| 1. |
- Rano, Jacqueline, et al.
(författare)
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Effects of acute psychological stress on athletic performance in elite male swimmers
- 2019
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 59:6, s. 76-1068
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: While physical activity has been shown to affect psychological as well as physiological stress responses, less research has explored the effects of acute stress on athletic performance. The current study hence aimed to investigate the effect of an Acute Psychological Stress (APS) provocation on performance and plasma lactate concentration during a following 200m swim race among male elite swimmers. Furthermore, associations between physiological stress responses (salivary cortisol and testosterone), and outcome measures (speed and lactate) were explored.METHODS: Twenty-three elite male swimmers participated in an experimental counterbalanced within-group repeated measures design consisting of an APS provocation followed by a 200m race and, on a separate day, a control race without prior stress exposure. Salivary cortisol and testosterone were collected prior to each race. Race time was recorded, and serum lactate were collected immediately following, and five min after completed race.RESULTS: Race speed was significantly slower (1.53 (95% CI: 0.08-2.79) seconds) following the APS provocation than under control conditions. Pre-race cortisol levels were positively associated with lactate response when preceding stress exposure was present (rho =.483 immediately, and rho=.429 five minutes post race, p's<0.05). Under control conditions however, both increased testosterone (rho= -657, p=0.001) and cortisol (rho= -.491, p=0.020) levels were associated with faster race times.CONCLUSIONS: The results indicated a negative impact of APS exposure on athletic performance. Further, potential beneficial effects on performance from physiological stress responses (as reflected by salivary cortisol and testosterone) may be diminished during performance following an APS provocation, compared with a regular non-provoked performance situation.
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| 2. |
- Ryman Augustsson, Sofia, et al.
(författare)
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Jump height as performance indicator for the selection of youth football players to national teams
- 2019
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Ingår i: Journal of Sports Medicine and Physical Fitness. - Turin : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 59:10, s. 1669-1675
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Tidskriftsartikel (refereegranskat)abstract
- Background: Different jump tests such as the Countermovement Jump (CMJ), Abalakov Jump (AJ) and Standing Long Jump (SLJ) are often used in practice to evaluate muscular power and functional performance in football. These tests are also used in different selection processes and talent identification, but the significance of the tests for the selection of youth players to national teams are relatively unknown. The aim of this study was to compare jump ability between youth football players selected or not selected for the national team.Methods: In this cross-sectional study, 22 players (aged 17±2 years), 11 national players (NP) and 11 non-national players (NNP) were evaluated in three different jump tests; CMJ, AJ and SLJ. Mean scores for the tests were analyzed and compared.Results: Significant differences were found between the groups regarding jump height in favor of the NP group in both the CMJ (NP 39.9±5.0 cm vs. NNP 34.2±4.9 cm, P=0.013) and the AJ (NP 47.1±5.4 vs. NNP 40.9±4.7, P=0.010). No group difference was found regarding jump length in SLJ (NP 246.2±17.9 vs. NNP 232.9±16.5, P=0.084).Conclusions: The results suggest that tests, measuring jump height, could be used as a performance indicator and part of the selection process of youth football players to national teams, whereas the use of jump length could be questioned. Copyright © 2019 Edizioni Minerva Medica
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| 3. |
- Aasa, Ulrika, et al.
(författare)
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A descriptive analysis of functional impairments and patho-anatomical findings in eight powerlifters
- 2020
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 60:4, s. 582-593
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Low back pain (LBP) is a common pain problem in powerlifters. There is a lack of evidence to guide powerlifters and health-care professionals in understanding the role of powerlifting in the development of LBP and treatment of injuries in powerlifters. This study aimed to describe functional impairments and patho-anatomical findings in eight powerlifters with and without LBP. METHODS: First, four powerlifters with LBP were recruited. Each powerlifter was then matched with a pain-free lifter (Control) by age, Body Mass Index and competition weight class. They all performed physical performance tests and were examined with magnetic resonance imaging. Four weeks prior to the examination the powerlifters also recorded training load. Powerlifters with LBP were also examined by a physiotherapist in order to define their pain and impairments. RESULTS: The four male powerlifters with LBP had a nociceptive pain associated with non-ideal squatting technique, higher flexibility in their lumbar spine than in their hips and patho-anatomical findings such as degenerated discs (four), spondylolysis (one) and spinal stenosis (one). However, the controls also showed similar functional impairments and patho-anatomical findings. CONCLUSIONS: Powerlifters with and without LBP show similar functional impairments and patho-anatomical findings. However, powerlifters' LBP seems associated with pain during movement and loading of the lumbar spine. The association and causation between specific functional impairments, patho-anatomical findings and LBP in powerlifters has to be further investigated in studies including more participants.
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| 4. |
- Alghadir, Ahmad H., et al.
(författare)
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Effect of voluntary teeth clenching and sitting posture on maximal static force of limb muscles
- 2019
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Ingår i: Journal of Sports Medicine and Physical Fitness. - Turin : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 59:5, s. 774-778
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: People clench their teeth to activate facial, neck and abdominal muscles when they need to generate heavy muscle force against large resistance like lifting heavy objects, in order to gain possible ergogenic advantage. These are termed as remote voluntary contractions. Aim of this study was to evaluate the effect of voluntary teeth clenching on maximal voluntary contraction of extensors and flexors of the knee, shoulder and elbow joints of the dominant side during slouch and unsupported upright sitting.METHODS: One hundred healthy young male adults (mean age 23.3 years) participated in this study. Maximal voluntary contraction was measured using a hand-held dynamometer.RESULTS: Jaw clenching caused different ergogenic effect during slouch versus unsupported sitting postures. The data revealed that during unsupported upright sitting, the effect of jaw clenching consistently results in larger maximal voluntary contraction of both extensor and flexor muscles of all the three studied joints. However, during slouch sitting, only the maximal voluntary contraction of extensors of elbow and flexors of knee were larger with clenched teeth position.CONCLUSIONS: Jaw clenching can affect the maximal voluntary contraction of limb muscles which is sitting posture dependent. Jaw clenching can consistently facilitate certain muscles of the upper and lower limbs to generate greater force production during upright sitting.
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| 5. |
- Bengtsson, Victor, et al.
(författare)
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Could the negative effects of static stretching in warm-up be restored by sport specific exercise?
- 2018
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 58:9, s. 1185-1189
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Static stretching (SS) is widely used in warm-up as it is generally believed to increase mobility and reduce the risk of injury; however, SS has been shown to induce transient negative effects on subsequent muscle performance. Interestingly, recent studies have shown that sport specific exercise could restore SS-induced negative effects on certain sports, especially of explosive muscular performance. Whether sport specific exercise could restore SS-induced negative effects on isokinetic muscle performance remains unclear.METHODS: The present study conducted two different warm-ups: 2-component warm-up and 3-component warm-up on 15 university students. Both protocols contained low intensity aerobic exercise and sport specific exercise, whereas the 3-component warm-up also contained SS which has been previously proven to induce negative effects on subsequent muscle performance. After the warm-ups, the subjects performed an isokinetic test on a Biodex. To make the sport specific exercise mimic the subsequent test, both included concentric isokinetic knee extension. During the tests, muscle performance of peak torque, mean power, and total work was recorded. Comparison of the measurements on each parameter between the two warm-ups was performed using paired t test.RESULTS: The comparisons did not reveal any significant difference in the measurement of any parameter between the two different warm-up protocols, and calculation of Cohen's revealed small effect sizes on all of the three variables.CONCLUSIONS: On basis of the present results and that the SS could induce transient negative effects on subsequent muscle performance, we concluded that the negative effects of the SS on the variables were restored by the isokinetic contractions.
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| 6. |
- Carlsson, Magnus, et al.
(författare)
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The acute effects of a short technique-intense training period on side-foot kick performance among elite female soccer players
- 2019
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 59:9, s. 1442-1449
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Previously, it was shown that elite soccer teams were 24% more likely to win matches if their passing effectiveness were increased by 1%. However, research interventions aiming to improve passing performance are scarce. The current study aimed to investigate the effect of a short technique-intense training period on side-foot kick performance among elite female soccer players.METHODS: Four side-foot kick tests were completed before and after a training period: kicking a stationary ball using match-relevant (SBRS) and maximal ball speed (SBMS), passing the ball on the move using match-relevant ball speed (RBRS), and repeated side-foot kicks onto a rebound-box with continuously increasing passing distance (RRB). The players were assigned to either the intervention group or the control group. The training intervention consisted of six 55-min training sessions with five side-foot kick exercises. Within-group and between-group differences were investigated using paired-samples t-test and Mann-Whitney U test, respectively.RESULTS: The intervention group improved the performance in the RBRS and RRB tests (both P < 0.05), but no differences were found for the SBRS and SBMS tests (both P > 0.05). No improvements were found for the control group independent of test condition (all P > 0.05). Significant between-group differences were found for the RBRS and RRB tests (both P < 0.05), whereas no differences were found for the SBRS and SBMS tests (both P > 0.05).CONCLUSIONS: The fundamental soccer skill of passing a moving ball was improved in elite female soccer players by a short technique-intense training period.
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| 7. |
- Fornasiero, Alessandro, et al.
(författare)
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Participation and performance by women and men in ski-mountaineering sprint races during the past decade
- 2023
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 63:6, s. 707-712
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The sprint is one of the two ski-mountaineering disciplines that will be held at the coming Milano Cortina 2026 Winter Olympics (Italy). To date little information exists on this novel Olympic discipline.METHODS: We characterized retrospectively the participation and performance in international male and female ski mountaineering sprint races from November 2012 to April 2022. Potential associations between sex and season with participation, as well as between sex, period, round and final ranking with parameters of performance were examined with linear-mixed models.RESULTS: The minimal performance time required for success (i.e., being eligible for the next round/winning a medal) decreased progressively from the qualifications (Qs) to the final (F). Finalists adopted a conservative strategy in the Qs, improving their performance in the quarter-finals (QFs) and semifinals (SFs). The best and second-best male skier and the best female skier improved their performances even further in the F, which appears to be a key feature for success. For women, the number of participants and level of competition increased over the decade, whereas male participation did not. During the last two seasons, male sprint winners performed relatively more slowly in the preliminary rounds leaving more room for improvement in the F, which could reflect increased specialization in this discipline.CONCLUSIONS: Our findings provide novel insights into ski-mountaineering sprint races that can guide competition strategies and could be of considerable importance in connection with the Milano Cortina 2026 Winter Olympics (Italy).
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| 8. |
- Haapala, Eero A., et al.
(författare)
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Association between cardiorespiratory fitness and metabolic health in overweight and obese adults
- 2022
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Ingår i: Journal of Sports Medicine and Physical Fitness. - Turin : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 62:11, s. 1526-1533
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Cardiorespiratory fitness (CRF) has been inversely associated with insulin resistance and clustering of cardiometabolic risk factors among overweight and obese individuals. However, most previous studies have scaled CRF by body mass (BM) possibly inflating the association between CRF and cardiometabolic health. We investigated the associations of peak oxygen uptake (V?O2peak) and peak power output (Wpeak) scaled either by BM-1, fat free mass (FFM-1), or by allometric methods with individual cardiometabolic risk factors and clustering of cardiometabolic risk factors in 55 overweight or obese adults with metabolic syndrome. METHODS: VO2peak and Wpeak were assessed by a maximal cycle ergometer exercise test. FFM was measured by air displacement plethysmo- graph and glucose, insulin, HbA1c, triglycerides, and total, LDL, and HDL cholesterol from fasting blood samples. HOMA-IR and metabolic syndrome score (MetS) were computed. RESULTS: VO2peak and Wpeak scaled by BM-1 were inversely associated with insulin (β=-0.404 to -0.372, 95% CI: -0.704 to -0.048), HOMAIR (β=-0.442 to -0.440, 95% CI: -0.762 to -0.117), and MetS (β=-0.474 to -0.463, 95% CI: -0.798 to -0.127). Other measures of CRF were not associated with cardiometabolic risk factors. CONCLUSIONS: Our results suggest that using BM-1 as a scaling factor confounds the associations between CRF and cardiometabolic risk in overweight/obese adults with the metabolic syndrome. © 2022 EDIZIONI MINERVA MEDICA.
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| 9. |
- Harringe, Marita L, et al.
(författare)
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Gymnasts' experiences and perception of a cruciate ligament injury.
- 2022
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 62:6, s. 812-821
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Gymnastics is a high injury risk sport including difficult technique. A cruciate ligament injury is common, though there are no evidence-based guidelines for return to gymnastics. The gymnasts' experiences may add specificity to a guideline. Therefore, the aim of the present study was to describe the gymnasts' experiences and perception of a cruciate ligament injury.METHODS: An embedded mixed methods design. Semi-structured interviews in 14 gymnasts between March and August 2018. The gymnasts represented a variation in age, sex, discipline, level of gymnastics, re- ruptures, associated injuries and return to gymnastics. The Knee Injury and Osteoarthritis Outcome Score, compared with age matched cruciate ligament injured gymnasts in the Swedish National Knee Ligament Registry, and the Tegner's Activity Score were supplements to the interviews. The interviews covered injury occasion, rehabilitation, return to gymnastics and current experience of the knee joint and were analyzed using qualitative content analysis with an inductive approach.RESULTS: The Knee Injury and Osteoarthritis Outcome Score was consistent with the Swedish National Knee Ligament Registry and showed low levels in the subscales Quality of Life and sports/recreation. One third reported Tegner's Score <6 supporting low levels in Sports/Recreation. The text analysis resulted in two parts "This really happened, cold facts" and "Prerequisites and hindrances for return to gymnastics." The gymnasts' narratives were similar and reached saturation.CONCLUSIONS: A cruciate ligament injury is a large trauma, and the physical and psychological demands must be understood. The results of the present study may be included in a framework for return to gymnastics, where the individual prerequisites and goals should be determined. The timeline within this framework would depend on the extent of the injury, expected time for healing and physical as well as psychological demands with respect to gymnastics' level. It may also include suggestions for different psychological strategies and performance enhancement techniques to increase the gymnasts' self-efficacy and encourage and motivate the gymnasts through the long and demanding rehabilitation.
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| 10. |
- Höög, Stefan, et al.
(författare)
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Incidence of acute injuries in Swedish gymnastics with a special focus on cruciate ligament injuries.
- 2023
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 63:5, s. 667-673
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Gymnastics is a sport with unique technical and physical demands. Elements of high rotational landing impacts may lead to severe injuries. In order to understand the risks of the sport and design injury prevention programs the magnitude of acute injuries must be understood. The aim was to investigate acute injuries, medical invalidity and injury costs in gymnastics using national insurance data.METHODS: Insurance data covering acute injuries in Swedish gymnastics from October 2015 to October 2020 were analyzed. All Swedish gymnasts with either a training or competition license were included (N.=333,932 licenses, 249,823 females; 84,109 males).RESULTS: A total of 1733 acute injuries were reported, and the injury incidence was 5.2 per 1000 gymnast years, with no differences between upper and lower body. The arm followed by the foot and the knee were body locations with highest injury incidence. Skeletal injuries were most common in the arm and foot, and ligament injuries in the foot and knee. The proportion of cruciate ligament injuries was 37% of all knee injuries and 5% of all acute injuries. No significant difference between male and female gymnasts was observed. The highest proportion of medical invalidity was found in the knee (33%), the foot (22%), and the arm (20%). Sixteen percent of all cruciate ligament injuries led to medical invalidity and was the injury causing highest costs to the insurance company.CONCLUSIONS: The knee was the third most common injury location and the injury causing the highest medical invalidity.
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| 11. |
- Iglesias, Xavier, et al.
(författare)
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Physiological demands of standing and wheelchair fencing in able-bodied fencers
- 2019
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 59:4, s. 569-574
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The purpose of this study was to determine the cardiorespiratory demands of standing and wheelchair (seated) fencing in a group of able-bodied fencers during simulated competitive bouts.METHODS: Participants were ten male able-bodied fencers of regional level with previous training experience in wheelchair fencing. After a standardised warm-up participants performed two series of simulated competitive épée bouts (5 and 15 touches) in a random order, either while standing or while sitting in a wheelchair. Expired gas was analyzed for oxygen consumption (V̇ O2) and respiratory exchange ratio (RER) and heart rate were continually monitored. Energy expenditure (EE) was subsequently calculated.RESULTS: V̇ O2, HR and EE peak responses were greater during standing than seated fencing (p< .05). Mean V̇ O2 during all ST bouts (5 and 15 touch) was 43% greater than in WC fencing (44.2 ± 7.8 vs. 25.1 ± 5.4 ml·kg-1·min-1). Mean HR during the standing 5 and 15 touch bouts was 91% ± 20% and 84% ± 7% of that recorded during the seated bouts. HR,V̇O2 and EE data also indicated that the 15-touch bouts were more physiologically demanding than the 5-touch bouts (P < .01). The HR-V̇ O2 relationship was similar between both fencing modes. The duration of the 5 and 15 touch bouts were shorter for the seated than the standing bouts (P < .01).CONCLUSIONS: The physiological demands of wheelchair fencing are lower than those for standing fencing. Furthermore, the physiology of 5 vs. 15 touch bouts, similar to those undertaken in fencing competition, also differs.
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| 12. |
- Mulder, Eric, et al.
(författare)
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Effects of dynamic apnea training on diving bradycardia and short distance swimming performance
- 2022
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 62:8, s. 1037-1044
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Apnea training enhances bradycardia and improves competitive apnea performance, and has been proposed as a training method for other sports, such as swimming. We evaluated the effects of apneic underwater swimming, i.e. dynamic apnea (DYN), in 9 competitive swimmers (TR) who completed ten DYN sessions over 2 weeks.METHODS: TR performed pre- and post-training tests including a static apnea test with continuous heart rate (HR) and peripheral oxygen saturation measurements, all-out 50m and 100m freestyle tests and an all-out DYN test. Control groups were competitive swimmers (SC; n=10) that trained swimming without DYN, and a non-swimmer group (AC; n=10) performing only static apnea tests.RESULTS: Post-training, TR mean±SD time for 50m freestyle improved from 25.51±2.01s to 24.64±2.02s (p<0.01) and for 100m from 55.5±4.2s to 54.1±4.4s (p<0.05). SC also improved their 100m time from 56.7±3.3s to 56.0±3.1s (p<0.01; p=0.07 between groups). Only TR performed DYN tests; DYN distance increased from 62.1±11.5m to 70.9±18.9m (p<0.05) while DYN speed decreased from 0.74±0.14m/s to 0.64±0.18m/s (p<0.01). Static apnea duration did not change in any of the groups, but HR-reduction was enhanced posttraining only in TR (24.8±14.8% to 31.1±10.9%, p<0.01; p<0.001 between groups).CONCLUSIONS: We conclude that 2 weeks of DYN training enhanced DYN performance, which may be caused by the enhanced apnea-induced diving bradycardia. Further research is required to determine whether DYN training enhances short distance freestyle swimming performance.
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| 13. |
- Sewry, N., et al.
(författare)
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Risk factors for not finishing an ultramarathon: 4-year study in 23,996 race starters, SAFER XXI
- 2022
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 62:5, s. 710-715
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Limited data support prerace medical screening to identify risk factors for not finishing an endurance running race. The aim of the study was to determine risk factors associated with not finishing an ultramarathon. METHODS: A prospective, cross-sectional study of Two Oceans ultramarathon (56 km) race starters who completed a prerace medical screening questionnaire. Race day environmental conditions were recorded on race day. Univariate analyses of risk factors associated with the did-not-finish (DNF) included race day factors and prerace medical screening history. RESULTS: Risk factors for DNF amongst 23,996 starters during the 56 km race included older age and females (P<0.0001). After adjusting for age and sex, the following were significant univariate risk factors: fewer years of running (P<0.0001), less previous race experience (P<0.0001), less training/racing per week (P=0.0002), lower average weekly training distance (P=0.0016), slower race vs. training speed (P<0.0001), lack of allergies (P=0.0100) and average wet-bulb globe temperature (P<0.0001). CONCLUSIONS: Females, older age, training-related factors (less training/racing, average weekly training distance, race vs. training speed) and average wet-bulb temperature, were risk factors for not finishing an ultramarathon. The results may not only assist runners and coaches in race preparation, but also have clinical implications for the medical planning prior to races.
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| 14. |
- Tillander, Bo, et al.
(författare)
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Associations between recreational runners anti-inflammatory drug use, coping strategies, and time loss due to injury and illness during preparations for a marathon event
- 2018
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : EDIZIONI MINERVA MEDICA. - 0022-4707 .- 1827-1928. ; 58:12, s. 1839-1843
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Due to the dominance of overuse injuries among runners, knowledge of how use of non-steroidal anti-inflammatory drugs (NSAIDs) and behavioral factors contribute to injury events is important. The aim of this study was to explore recreational marathon runners strategies for coping with injury and illness, including use of drugs for control of pain and inflammation, and to investigate whether these strategies were associated with the 1-year prevalence of time-loss injury and illness. METHODS: An online questionnaire was used for data collection in this cross-sectional study. The population consisted of runners who had registered for a marathon (N.=341). Strategies used to understand and manage perceptions of injury and illness were measured with the Brief COPE instrument and the use of NSAIDs was investigated. RESULTS: Complete survey data were provided by 161 runners (47%). 42% reported NSAID use. A notable injury in the past year was reported by 43%, and 19% reported having had a time-loss illness episode. Runners who reported NSAID use in the past year reported significantly fewer time-loss injuries (P=0.003). Time loss due to illness only showed a negative correlation with using emotional support for coping (P=0.010) and a positive correlation with self-blame (P=0.039). CONCLUSIONS: Runners stating NSAID use reported fewer time-loss running injuries than non-NSAID users. Time loss due to illness showed different correlates with NSAID use and coping strategies than time loss due to injury, i.e. no association with drug use, less use of emotional support for coping and more use of self-blame.
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| 15. |
- Wikström-Frisén, Lisbeth, 1955-, et al.
(författare)
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Effects on power, strength and lean body mass of menstrual/oral contraceptive cycle based resistance training
- 2017
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 57:1-2, s. 43-52
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The purpose of this study was to investigate the effects of menstrual and oral contraceptive cycle on a high frequency periodized leg resistance training in trained women. METHODS: Two groups performed high frequency leg resistance training for two weeks of each menstrual/oral contraceptive cycle for four months. The remaining part of the cycle they performed the leg training once a week. Group 1 (N.=19) trained with high frequency (5 times-w-') during the first two weeks of each cycle, and group 2 (N.=19) during the last two weeks of each cycle. A control group (N.=21) performed regurlar (3 times.w(-1)) leg resistance training for four months. RESULTS: Significant increase in squat and countermovement jump, and peak torque values in hamstrings for group 1 were observed, but not in group 2. In the control group an increase in squat and countermovement jump, and peak torque (only left hamstring) was also observed. There was also a significant increase in lean body mass of the legs in group 1 only. There were no evident differences in the training effects between women with or without oral contraceptive. CONCLUSIONS: The high frequency periodized leg resistance training during the first two weeks of the menstrual cycle is more beneficial to optimize training than in the last two weeks. Resistance training during the first two weeks of the menstrual cycle even resulted in a larger gain of lean body mass than regular training.
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| 16. |
- Wikström-Frisén, Lisbeth, et al.
(författare)
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Increasing training load without risking the female athlete triad : menstrual cycle based periodized training may be an answer?
- 2017
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 57:11, s. 1519-1525
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: An improved muscle strength are of great importance in many sports, hence an increased understanding on how to generate optimal strength training programs in women without negative side effects that may lead to the female athlete triad are essential. The purpose of this study was to investigate potential negative effects of high frequency periodized menstrual/OC cycle based leg resistance training on components in the female athlete triad.METHODS: Fifty-nine women, with experience of resistance training and with regular menstrual/OC cycles were included in the analyses. The participants were randomly assigned a training program consisted of high frequency leg resistance training, periodized to the first two weeks (group 1) or the last two weeks (group 2) of each cycle, or to a control group performing regular training, during four consecutive menstrual/OC cycles. The main analysis was the pre-to-post change of sex and growth hormones, cortisol, total body fat mass, bone mineral density in the spine. We further examined the participants’ own experience of the training programs.RESULTS: No significant negative impact on sex and growth hormones, cortisol, total body fat mass and bone mineral density in the spine, was detected in any of the groups. Moreover, the women in group 1 experienced their training program as positive.CONCLUSIONS: The high frequency periodized leg resistance training was not associated with exercise-related negative consequences on components in the female athlete triad. Moreover, the training was well accepted when performed during the first two weeks of each cycle.
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| 17. |
- Yousefian, F., et al.
(författare)
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Physical workload and fatigue pattern characterization in a top-class women's football national team: a case study of the 2019 FIFA Women's World Cup
- 2021
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 61:8, s. 1081-1090
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: With the growing scientific interest in women's football it is critical to understand the match demands and fatigue patterns during a top-class women's competition. METHODS: Physical characteristics and performance of top-class women football matches during the 2019 FIFA Women's World Cup was investigated from data collected using global positioning system for 21 outfield players during the tournament. RESULTS: Relative total distance (TD; m.min(-1)) was moderately lower (P=0.05, ES:0.6) in the final match (96.1 +/- 5.0 m.min(-1)) compared to the first (104.1 +/- 5.9 m.min(-1)) match. Performance in relative total high-speed running (THSR; m.min(-1)) declined -27.5% (P=0.05) throughout the tournament following peak performance in the third match (M3) (5.3 +/- 1.7 m.min(-1)). Match performance between halves was reduced -25.4 +/- 0.13% (P=0.05, ES:1.2-2.3) across all measures in M3. Relative high-intensity running (HIR; 25.9 +/- 3.5 m.min(-1)) and THSR (9.8 +/- 1.5 m.min(-1)) were greater (P=0.05, ES:0.2-0.7) for forwards, while midfielders performed greater (P=0.05, ES:0.6) relative total distance (102.0 +/- 5.5 m.min(-1)), compared to central defenders (HIR: 16.1 +/- 3.7 m.min(-1); THSR: 3.1 +/- 1.6 m.min(-1); TD: 92.5 +/- 5.7 m.min(-1)). Reductions in relative HIR between halves (-10.9%), within the first half (-31.0%), and the start and end of the match (-36.9%) were most pronounced for midfielders (P=0.05, ES:0.6-2.3). Across all matches, relative THSR performance was reduced, with moderate to large differences (P=0.001, ES: 0.7-0.8) observed between halves, within the first half, and throughout the match. CONCLUSIONS: In conclusion, specific fatigue patterns observed within and between matches throughout the women's World Cup, may be influenced by playing positions, the rank of the opposition, as well as the stage of the tournament.
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| 18. |
- Yu, Ji-Guo, et al.
(författare)
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Potential effects of long term abuse of anabolic androgen steroids on human skeletal muscle
- 2020
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 60:7, s. 1040-1048
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: We have previously evaluated muscle functions and morphology in power athletes of long term (5 to15 years) abuse of anabolic androgen steroids (AAS; Doped) and in clean power athletes (Clean), and observed significant improvements in both muscle morphology and muscle functions in Doped. To our knowledge, the effects of long term AAS abuse on human muscle protein profile have never been studied.METHODS: The study examined further the muscle biopsies using a two-dimensional difference gel electrophoresis (2D DIGE) for proteomic screening and protein expression. Cellular localization/distribution of specific proteins identified by proteomic analysis was examined using immunohistochemistry (IHC).RESULTS: Different protein profiles were observed between Doped and Clean, and a valid orthogonal projection of latent structure discriminant analysis model was built (N = 16, X = 5, R2 = 0.88/Q2 = 0.84, p = 0.0005), which separated Doped from Clean. Liquid chromatography followed by tandem spectrometry identified 14 protein spots (representing nine different proteins) of significant difference in relative quantity (p < 0.05), of which nine spots were down-regulated in Doped compared with Clean. IHC revealed no significant alteration in cellular localization in phosphoglucomutase-1 and heat shock protein beta-1, but indeed in two reference proteins desmin and F-actin in Doped.CONCLUSIONS: Long term abuse of AAS in combination with training is potentially associated with alterations in skeletal muscle protein profile and protein expression, and structural proteins rather than non-structural proteins are preferentially affected in cellular localization/distribution.
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| 19. |
- Alricsson, Marie, et al.
(författare)
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Self-reported health, physical activity and prevalence of complaints in elite cross-country skiers and matched controls
- 2005
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 45:4, s. 547-552
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Tidskriftsartikel (refereegranskat)abstract
- Aim. The purpose of this study was to compare physical health, physical activity and location for possible symptoms in high school students with cross-country skiers of the same age from ski high schools. Another aim was to study back pain with regards to influence on skiing.Methods. The subjects studied were: 92% (n=120) of all Swedish cross-country skiers at ski high schools and 68% (n=993) of regular high school students from the North part of Sweden answered a reliable questionnaire (r=1) with regards to health, physical activity and location of possible symptoms/injuries during the last 3 months. Furthermore, the skiers answered questions on possible ski related back pain.Results. All skiers were active also in other sports compared with 26% of the controls and at considerably higher levels of physical effort than the controls; 92% of the skiers and 76% of the controls described themselves as healthy, meaning "very good" or "good" (P=0.0001); 55% of the skiers and 64% of the controls reported recent symptoms (P=0.06); 47% of the skiers reported previous or present complaints of back pain, mainly low back pain, which could be relieved by changing body position from a flexed to a more extended one while skiing, and 77% reported their back pain to disappear during rest.Conclusion. These results show the need for encouraging regular high school students to participate in sport. It also shows the importance of introducing preventative strategies regarding back pain to long-distance cross-country skiers, who are exposed to a prolonged flexed position of their back.
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| 20. |
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| 21. |
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| 22. |
- Helge, E. Wulff, et al.
(författare)
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BMD in elite female triathletes is related to isokinetic peak torque without any association to sex hormone concentrations
- 2012
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 52:5, s. 489-500
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Tidskriftsartikel (refereegranskat)abstract
- Aim. Female endurance athletes suffering from low energy availability and reproductive hormonal disorders are at risk of low BMD. Muscle forces acting on bone may have a reverse site-specific effect. Therefore we wanted to test how BMD in female elite triathletes was associated to isokinetic peak torque (IPT) and reproductive hormone concentrations (RHC). A possible effect of oral contraceptives (OCON's) is taken into consideration. Methods. Eight female elite triathletes (training 8-24 hrs/wk) and seven sedentary controls, age 21-37 years, participated. Total body and regional BIVID (g.cm(-2)) were measured by DXA. IPT were measured during knee extension, and trunk extension and flexion (Nm). Serum RHC and biochemical bone markers were evaluated. Energy balance was estimated from 7-days training-and weighed food records. Results. Despite a high training volume, BMD in triathletes was not higher than in controls. In triathletes trunk flexion IPT, but not RHC, was a strong predictor of BMD in both total body and femur (0.70
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| 23. |
- Laurent, C M, et al.
(författare)
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Effect of gender on fatigue and recovery following maximal intensity repeated sprint performance
- 2010
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 50:3, s. 243-253
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Tidskriftsartikel (refereegranskat)abstract
- Aim. This study investigated the effects of gender on repeated, maximal-intensity intermittent sprint exercise following variable day-to-day recovery periods.Methods. Sixteen volunteers (8 men, 8 women) performed four trials of high-intensity intermittent sprint exercise consisting of three bouts of eight 30 m sprints (total of 24 sprints). Following completion of the baseline trial, in repeated-measures design, participants were assigned, in counter-balanced order, variable recovery periods of 24, 48, and 72 h whereupon they repeated an identical exercise trial.Results. Results from a series of 4 (trial) x 3 (bout) repeated measures ANOVAs revealed men produced significantly (P < 0.01) faster times throughout all bouts and trials of repeated sprint exercise. Additionally, women exhibited significantly lower (P < 0.05) blood lactate concentration and significantly lower (P < 0.05) decrement in performance, indicating increased resistance to fatigue during repeated exercise sessions. There were no significant differences (P > 0.05) between genders for heart rate or rating of perceived exertion during or following trials. There were no significant differences for overall sprint performance within either gender among trials.Conclusions. These results indicate men, while able to produce higher absolute power outputs (i.e., lower sprint time), demonstrate higher decrement scores within a trial compared to women, thus suggesting women may recover faster and fatigue less. Also, gender differences affecting recovery within in a trial were observed to be diminished between trials (i.e., day-today recovery) of maximal intermittent sprint work evidenced by the observed stability of performance between trials following various recovery durations.
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| 24. |
- Malmgren, Andreas, et al.
(författare)
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Cardiac dimensions and function in female handball players.
- 2015
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Minerva Medica. - 0022-4707 .- 1827-1928. ; 55:4, s. 320-328
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Long-term intensive endurance training leads to increased left ventricular mass and increased left ventricular end-diastolic and left atrial end-systolic diameters. Different types of sports tend to give rise to distinct morphological forms of the athlete's heart. However, the sport-specific aspects have not been fully investigated in female athletes. The purpose of the present study was to investigate differences in left and right cardiac dimensions, cardiac volumes, and systolic and diastolic function in elite female handball players compared to sedentary controls. METHODS: A cross-sectional study of 33 elite female handball players was compared to 33 matched sedentary controls. Mean age was 21.5±2 years. The subjects underwent echocardiography examinations, both 2-dimensional (2DE) and 3-dimensional (3DE). Cardiac dimensions and volumes were quantified using M-mode, 2DE and 3DE. Systolic and diastolic left ventricular functions were also evaluated. All cardiac dimensions and volumes were adjusted for body surface area (BSA). RESULTS: Left atrium and left ventricle volumes were significantly (P<0.001) larger in elite female handball players compared with sedentary controls. Even right atrium area as well as right ventricular end-diastolic and end-systolic area were significantly (P<0.001) larger in elite female handball players. Significant differences were observed in three out of five systolic parameters. Most diastolic function parameters did not differ between the two groups. CONCLUSION: The findings from the present study suggest that similar cardiac remodeling takes place in elite female handball players as it does in athletes pursuing endurance or team game sports.
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| 25. |
- Mandroukas, A, et al.
(författare)
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Deltoid muscle fiber characteristics in adolescent and adult wrestlers.
- 2010
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 50:2, s. 113-20
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Tidskriftsartikel (refereegranskat)abstract
- Our findings suggest that the observed muscle fiber profile in the deltoid muscle of wrestlers may represent an adaptation based on the mechanical and biochemical demands of the long-term training. Such adaptations are linked to the specific characteristics of the training program, the level and the previous training experience of the wrestlers.
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| 26. |
- Sjökvist, Jesper, et al.
(författare)
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The effect of incline on sprint and bounding performance in cross-country skiers
- 2015
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 55:5, s. 405-414
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Tidskriftsartikel (refereegranskat)abstract
- Aim. Aim of the present study was to investigate performance and kinematics of cross-country skiers during sprint running and bounding on different inclines, in relationship to maximal strength, power and skiing performance. Methods. On day one, the maximal strength of 14 elite skiers was tested using a mid-thigh isometric pull and maximal relative leg power determined using squat and countermovement jumps. Day two involved 15-m maximal sprints and 5-step bounding at 0 degrees, 7.5 degrees and 15 degrees inclines. From video recordings sprint, step, contact and flight times; step length and frequency; total number of sprint steps and average bounding velocity were determined. Skiing performance was assessed using International Ski Federation (FIS) points from the preceding season and compared to strength, power, bounding and sprint performance, and kinematics. Results. On steeper inclines sprint time was higher and bounding distance shorter (both P<0.001), and step frequency during sprinting and bounding, reduced and increased respectively (P<0.001). Isometric maximal strength correlated strongly with bounding distance on the two steeper inclines (r=0.76 and 0.83). Squat and countermovement jump heights correlated moderately with sprint performance at both 7 degrees and 15 degrees, and bounding performance on all three inclines (r=0.55-0.65). The distance bounded uphill correlated moderately with FIS points (r=-0.55 and -0.67). Conclusion. Incline influenced sprinting and bounding performance and kinematics. Maximal leg power is important for both sprinting and bounding uphill, while maximal strength is important for the latter. The skiers with better FIS rankings bounded farther on steeper inclines, suggesting that this capacity is beneficial for cross-country skiing performance.
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| 27. |
- Sperlich, Billy, et al.
(författare)
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Cardiorespiratory, metabolic and hormonal responses during open-wheel indoor kart racing
- 2014
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 54:4, s. 475-480
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Tidskriftsartikel (refereegranskat)abstract
- AIM: This study aimed to quantify the cardiorespiratory, metabolic and hormonal responses of elite open-wheel indoor kart racers.METHODS: Ten male racers (age: 21±3 yrs; height: 1.92±0.06 m, body mass: 76.0±5.9 kg) participated in a racing tournament. Their peak oxygen uptake and heart rate were assessed by a ramp test (100 W, increase 30 W·min-1) in the laboratory. During the racing itself, the cardio-respiratory and accelerometer values were recorded and pre- and post-race levels of blood lactate and salivary cortisol were determined.RESULTS: The average peak values for all of the drivers with respect to oxygen uptake and heart rate were 4.5±0.8 L·min-1 (56.7±7.9 mL·min-1·kg-1) and 193±5 beats·min-1, respectively. Overall, 28.3±3.3 laps were completed during 30-min of racing. Acceleration forces for the entire test averaged 1.20±0.51 G (maximum: 3.30 G), declining from the first 10 min until the end of racing (P<0.03). The oxygen uptake (~20 mL·min-1·kg-1), heart rate (~133 beats·min-1), respiratory exchange ratio (~0.96) and ventilation (~70 L·min-1) observed indicated moderate cardio-respiratory responses. Blood lactate concentration was significantly higher after the race than before but remained at <2 mmol·L-1 (P<0.01; effect size: 1.62).CONCLUSION: There were no differences between salivary cortisol levels before and after the race (P<0.06; effect size: 0.49). Directly after the race, the drivers rated their perceived exertion on Borg’s scale as 11.1±1.3. The present data revealed that the psycho-physical exertion associated with a 30-min open-wheel indoor kart race is moderate.
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| 28. |
- Sperlich, Billy, et al.
(författare)
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Physiological effects of a new racing suit for elite cross country skiers
- 2011
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707 .- 1827-1928. ; 51:4, s. 555-559
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Tidskriftsartikel (refereegranskat)abstract
- AIM: The aim of this paper was to investigate the influence of the new cross country racing suit, designed for the Olympic Winter Games in Vancouver 2010, on cardio-respiratory, thermoregulatory and perceptual responses.METHODS: Six elite cross country skiers (29±6 years, peak oxygen uptake 73.2±6.9 mL·min-1·kg-1) performed two exercise bouts wearing either the 2009 or the 2010 racing suit. Bouts consisted of incremental testing on roller skis (12 km·h-1 at 5° inclination; 11 km·h-1 at 6° inclination and 12 km·h-1at 8° inclination for six minutes).RESULTS: During increasing intensities, significantly lower values were found for oxygen uptake, minute ventilation, RER and heart rate when wearing the new suit compared to the old one (P<0.05; effect sizes: 0.21-4.00). Core temperature was lower with the new suit during steps 2 and 3 (P<0.05, effect size: 1.22-1.27). Also, mean skin temperature was lower during the last increment (P<0.05, effect size: 0.87).CONCLUSION:The new 2010 racing suit, developed specifically for the Olympic Winter Games in Vancouver 2010, demonstrated lower values for oxygen uptake, minute ventilation, heart rate, skin and core temperature, ratings of thermal and sweat sensation when compared to the 2009 racing suit.
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| 29. |
- Rago, Vincenzo, et al.
(författare)
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Switching between pitch surfaces: practical applications and future perspectives for soccer training
- 2019
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707. ; 59:3, s. 510-519
-
Tidskriftsartikel (refereegranskat)abstract
- Soccer training and completion is conventionally practiced on natural grass (NG) or artificial turf (AT). Recently, AT pitches for training / competition, and of unstable surfaces for injury prevention training has increased. Therefore, soccer players are frequently exposed to variations in pitch surface during either training or competition. These ground changes may impact physical and physiological responses, adaptations as well as the injury. The aim of this review was to summarize the acute physical and physiological responses, chronic adaptations, and injury risk associated with exercising on different pitch surfaces in soccer. Eligible studies were published in English, had pitch surface as an independent variable, and had physical, physiological or epidemiological information as outcome variables. Specific data extracted from the articles included the training response, training adaptations or injury outcomes according to different pitch surfaces. A total of 224 studies were retrieved from a literature search. Twenty articles met the inclusion criteria: 9 for acute physical and physiological responses, 2 for training adaptations and 9 for injury assessment. The literature lacks consistent evidence regarding the effects of pitch surface on performance and health outcomes in soccer players. However, it seems that occasionally switching training surfaces seems a valuable strategy for focusing on specific musculoskeletal queries and enhancing players’ fitness. For instance, sand training may be occasionally proposed as complementary training strategy, given the recruitment of additional musculature probably not involved on firmer surfaces, but the possible training-induced adaptations of non-conventional soccer surfaces (e.g., sand) might potentially result into a negative transfer on AT or NG. Since the specific physical demands of soccer can differ between surfaces, coaches should resort to the use of non-traditional surfaces with parsimony, emphasizing the specific surface-related motor tasks, normally observed on natural grass or artificial turf. Further studies are required to better understand the physiological effects induced by systematic surface-specific training, or switching between pitch surfaces.
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Dencker, Magnus, et al.
(författare)
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Aerobic capacity related to cardiac size in young children.
- 2013
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707. ; 53:1, s. 42-47
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Tidskriftsartikel (refereegranskat)abstract
- Aim:Aerobic capacity, defined as peak oxygen uptake (VO2PEAK), is generally considered to be the best single marker for aerobic fitness. We assessed if VO2PEAK is related to different cardiac dimensions in healthy young children on a population base. Methods: In a cross-sectional study, 245 children (137 boys and 108 girls) aged 8-11 years, were recruited from a population based cohort. VO2PEAK (ml/min-1/kg-1) was assessed by indirect calorimetry during a maximal exercise test. DXA-scan was used to measure lean body mass (LBM) and total fat mass (TBF). Echocardiography, with 2-dimensional guided M-mode, was performed in accordance with current guidelines. Left ventricular end-diastolic diameter (LVDD) and left atrial end-systolic diameter (LA) were measured, and left ventricular mass (LVM) was calculated. Results: Univariate correlations were found between VO2PEAK versus LVDD r=0.44 and LA r=0.27 (both P<0.05) and LVM r=-0.06 (NS) in boys. Corresponding values for girls were; 0.55, 0.34 (both P<0.05) and 0.11 (NS). Multiple regression analysis with VO2PEAK as dependent variable and inclusion of LBM, TBF, sex, age, Tanner stage, and maximal heart rate as independent variables showed that 67% of the total variance of VO2PEAK could be explained by these variables. Including LVDD or LA in the model, added 1% additional explained variance. Conclusion: Findings from this population based cohort of young healthy children show that multiple cardiac dimensions at rest are related to VO2PEAK. However, the different cardiac dimensions contributed very little to the added explained variance of VO2PEAK.
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| 35. |
- Dencker, Magnus, et al.
(författare)
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Importance of epoch length and registration time on accelerometer measurements in younger children.
- 2012
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707. ; 52:2, s. 115-121
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Tidskriftsartikel (refereegranskat)abstract
- AIM: The aim of this study was to investigate the effect of epoch length on accumulation of minutes of physical activity per day over a spectrum of intensities, and the effect that selection of number of hours of acceptable registration required per day had on number of days that were considered acceptable. METHODS: Participants were 696 children (369 boys and 327 girls) aged 6.7±0.4 yrs, from a population-based cohort. Physical activity was assessed by the Actigraph accelerometer for four days. RESULTS: Main findings were that epoch length had a profound impact on accumulation of minutes of physical activity per day for higher intensities, whereas it had no effect on mean counts per minute. The chosen number of hours for an acceptable registration per day heavily influenced the number of days that were considered acceptable. CONCLUSION: The findings in the present investigation should be taken into consideration when planning objective measurements of daily physical activity in younger children, and highlight the need for setting international recommendations for physical activity measurements with accelerometers, if different studies are to be comparable
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Karlsson, Magnus, et al.
(författare)
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Groin pain and soccer players: male versus female occurrence.
- 2014
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707. ; 54:4, s. 487-493
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Tidskriftsartikel (refereegranskat)abstract
- Groin pain is common in soccer players. Comparison of results from different studies, especially between genders, is difficult as studies use different definitions and data collection procedures. Therefore we conducted a study of both male and female soccer players enabling direct gender comparison.
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| 40. |
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| 41. |
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| 42. |
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| 43. |
- Osada, T., et al.
(författare)
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Differences in exercising limb blood flow variability between cardiac and muscle contraction cycle related analysis during dynamic knee extensor
- 2006
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Ingår i: Journal of Sports Medicine and Physical Fitness. - 0022-4707. ; 46:4, s. 590-597
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Tidskriftsartikel (refereegranskat)abstract
- Aim. Blood flow in peripheral conduit arteries during steady-state, dynamic exercise, can be estimated noninvasively with Doppler ultrasound, by measuring the conduit arterial diameter and the mean blood velocity averaged over consecutive cardiac beat-by-beat cycles (BBcycle) or muscle contraction-relaxation cycles (CRcycle). The precise impact fluctuations in the 1-BBcycle- or 1-CRcycle-rate may impose on the average blood flow measurements has previously not been clearly defined. The hypothesis investigated in the present study was that the blood flow measurements obtained, and its variability, during exercise, may differ between the 1-BBcycle and 1-CRcycle at incremental exercise intensities; as the BBcycle-measurements may be influenced by transient alterations in heart rate; whereas the CRcycle-measurements are dependent on the muscle contraction-relaxation frequencies independent of the exercise intensities per se. The main purpose was therefore to determine if fluctuations in blood flow for 1-BBcycle and 1-CRcycle varies at incremental exercise intensities (work rates) using the one-legged dynamic knee-extensor exercise (DKE) model. Methods. Limb femoral artery blood flow (LBF) was determined, for 1-BBcycle and 1-CRcycle, in 8 healthy male subjects during 4-min of steady-state DKE at 60 contractions per minute at 10, 20,30 and 40 W. The variability of LBF was determined from the coefficients of variation (CVLBF). Results. The CVLBF for the CRcycle-measurements at each work rate were similar (P=NS). The CVLBF for the BBcycle-measurements were higher (P<0.05) at 40 W compared to at 10 W. Furthermore, the CVLBF for the 1-BBcycle was higher (P<0.05) than for the 1-CRcycle at 30 and 40 W, despite almost identical mean LBF values for the BBcycle- and the CRcycle-measurements at each exercise intensity. Conclusions. The present data suggests that estimates of LBF at slightly higher exercise intensities such as above 30 W, for a few number of consecutive BBcycle renders a higher variability than for CRcycle-measurements. This may consequently result in slight over- and under-estimations of LBF compared to the CRcycle-measurement.
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| 44. |
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| 45. |
- Rago, Vincenzu, et al.
(författare)
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Variability of activity profile during medium-sided games in professional soccer
- 2019
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Ingår i: The Journal of Sports Medicine and Physical Fitness. - 1827-1928. ; 59:4, s. 547-554
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In Southern European countries it is very frequent to perform medium-sized games (MSG) as last training drill. We analyzed the individual variability and changes in activity patterns during MSG throughout the preseason. METHODS: Activity profile during MSGs (10v10+goalkeepers, duration: 10-min, field length: 50 m, width: 90 m, area per player: 204.5 m2) was quantified using a GPS in 14 professional male players (6 defenders, 5 midfielders 5 and attackers). RESULTS: Inter-individual variability was higher for high-intensity (HIR), very-high speed (VHS), maximum acceleration (Accmax) and maximum deceleration (Decmax) distance (CV=25.2 to 43.3%), compared to total distance (TD), total acceleration (Acctot) and total deceleration (Dectot) distance (CV= 8.3 to 18.3 %). Defenders showed higher variability in TD, HIR, VHS, Acctot and Dectot (ES= 1.30 to 11.28) compared to the other field positions, whereas attackers showed higher variability in HIR, VHS Accmax and Decmax (ES=-4.92 to 2.07) than other the field positions. Variability in TD regularly increased (ES= -2.13 to -0.91) towards the end of the preseason, while HIR and VHS variability tended to increase over the 3rd and the 4th preseason week (ES=-0.94 to -3.05). However, the behavior of variability across the preseason period was more unpredictable for Acctot and Dectot, both decreasing in the 3rd week (ES= 0.70 to 1.20), while Decmax increased in the 4th week (ES=-0.91±0.59). CONCLUSIONS: During MSGs, individual variability of activity differs among field positions, and tends to increase with either speed or acceleration intensity, underlining the need of an individualized approach for training load monitoring.
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| 46. |
- Rips, Leho, et al.
(författare)
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Severe deficiency of vitamin D has no negative effect on physical performance during military training.
- 2023
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Ingår i: The Journal of sports medicine and physical fitness. - 1827-1928. ; 63:2, s. 329-338
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Tidskriftsartikel (refereegranskat)abstract
- Decreased physical fitness and inferior physical performance are potentially life-threatening risk factors in a combat situation. To examine the effect of vitamin D on physical performance, a prospective study of young men conscripts in the Estonian Army was designed. The hypothesis of the study was that severe deficiency of vitamin D has a negative effect on physical performance.All conscripts (N.=410) entering 10-month military service in July 2015 at the Kuperjanov Battalion were asked to participate. Initially, a total of 98 conscripts volunteered to participate. A prospective longitudinal study with a 10-month follow-up period was performed. The Army Physical Fitness Test (APFT) was performed three times, and hand grip strength, and blood serum values of 25(OH)D, parathyroid hormone (PTH) and calcium (Ca) were measured four times.A significant decrease in the levels of 25(OH)D compared with baseline values were found, with a lowest mean value of 31.9 nmol/L in March 2016 (P<0.001). No significant differences were found in serum Ca levels. In March 2016, PTH was significantly higher in the severe deficiency group (<25 nmol/L of 25(OH)D) (P=0.02). No significant differences were found in terms of the APFT or hand grip strength between conscripts with severe deficiency of 25(OH)D or values >25 nmol/L. The main finding of the present study was that severe 25(OH)D deficiency was common among male conscripts during the winter season but had no negative effect on physical performance in terms of the APFT test and hand grip strength test.Severe vitamin D deficiency during the winter season is common but has no negative effect on physical performance in young, physically active men in military service.
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| 47. |
- Li, SS, et al.
(författare)
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Autocrine regulation of T cell motility by calreticulin-thrombospondin-1 interaction
- 2005
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Ingår i: Journal of immunology (Baltimore, Md. : 1950). - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 174:2, s. 654-661
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms regulating T lymphocyte migration within the extracellular matrix are not understood. We show in this study that the thrombospondin-1 binding site of calreticulin, spanning aa 19–32, is a major triggering factor for T cell motility and migration within a three-dimensional collagen type 1 matrix, and that exogenous motogenic factors such as chemokines can stimulate migration via a calreticulin-thrombospondin-1 pathway. Endogenous calreticulin binding to the N-terminal domain of endogenous thrombospondin-1 elicited a motogenic signal to the T cells through the C-terminal domain of thrombospondin-1 and its cell surface receptor integrin-associated protein (CD47). Our data further revealed that thrombospondin-1 was expressed on the cell surface with a high turnover, and that PI3K and the Janus family of tyrosine kinases were required for T cell motility mediated through calreticulin, thrombospondin-1, and CD47. These results unveil an autocrine mechanism of calreticulin-thrombospondin-1-CD47 interaction for the control of T cell motility and migration within three-dimensional extracellular matrix substrata.
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| 48. |
- Korchuganova, O. A., et al.
(författare)
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Microstructural evolution of Fe-22%Cr model alloy under thermal ageing and ion irradiation conditions studied by atom probe tomography
- 2016
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 477, s. 172-177
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructure evolution during ion irradiation of two thermally aged binary Fee22Cr alloys has been investigated using atom probe tomography. Specimens aged at 500 °C for 50 and 200 h were irradiated by 5.6 MeV Fe ions at room temperature up to fluences of 0.3 × 1015 ions/cm2 and 1 × 1015 ions/cm2. The effect of irradiation on the material nanostructure was examined at a depth of 1 ?m from the irradiated surface. The analysis of Cr radial concentration functions reveals that dense ??-phase precipitates in the 200 h aged alloy become diffuse and thereby larger when subjected to irradiation. On the other hand, less Cr-enriched precipitates in the alloy aged for 50 h are less affected. The CreCr pair correlation function analysis shows that matrix inhomogeneity decreases under irradiation. Irradiation leads to a decrease in the number density of diffuse clusters, whereas in the case of well-developed precipitates it remains unchanged.
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| 49. |
- Hemmingsson, Carl, et al.
(författare)
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Hydride vapour phase epitaxy growth and characterization of thick GaN using a vertical HVPE reactor
- 2007
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 300:1, s. 32-36
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Tidskriftsartikel (refereegranskat)abstract
- Growth of 2-inch diameter bulk GaN layers with a thickness up to 2 mm is demonstrated in a vertical hydride vapour phase growth reactor. Morphology, dislocations, optical and electrical properties of the material have been investigated using atomic force microscopy, optical microscopy, decorative etching in hot H3PO4, Hall measurements and low-temperature photoluminescence. Atomic force microscopy reveals a two-dimensional step flow growth mode with step bunching for layers with a thickness of 250 µm. As the growth proceeds, the morphology is changed to a hill and valley structure. The EPD was determined to 5×105 cm-2 for a 2 mm thick layer. The Hall mobility and the carrier concentration were determined. For a 1.7 mm thick layer at 300 K the mobility and the carrier concentration is 520 cm2/V s and about 4×1017 cm-3, respectively. Low-temperature photoluminescence spectra measured on a 350 µm thick freestanding layer show the DBE line at 3.4707 eV with a full-width half-maximum of 1 meV, confirming a stress free GaN layer. © 2006 Elsevier B.V. All rights reserved.
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