| 11. |
- Hallman, David, et al.
(författare)
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Effect of an aerobic exercise intervention on cardiac autonomic regulation : A worksite RCT among cleaners
- 2017
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Ingår i: Physiology and Behavior. - : Elsevier BV. - 0031-9384 .- 1873-507X. ; 169, s. 90-97
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveThe aim of this randomized controlled trial (RCT) was to determine whether aerobic exercise during work hours affects cardiac autonomic regulation in cleaners characterized by high levels of occupational physical activity and poor cardiorespiratory fitness.MethodEligible cleaners (n=116) were randomized to an aerobic exercise group (n=59) or a reference group (n=57) with lectures. The intervention group received two 30-min sessions per week of supervised aerobic exercise over 4 months. Diurnal measurements of heart rate variability (HRV) and physical activity (accelerometry) were obtained at baseline and at 4-month follow-up. Time and frequency domain indices of HRV were derived during work, leisure time and sleep to evaluate cardiac autonomic regulation. Linear mixed models were used to determine the effect of the intervention on HRV indices, with adjustment for age, gender and daily use of antihypertensive and/or heart medication.ResultsCompared with the reference group, the exercise group increased all HRV indices apart from a reduction in LF/HF ratio from baseline to follow-up both during work (p<0.05) and leisure (p<0.05). In contrast, during sleep, the HRV indices tended to decrease in the exercise group compared with the reference group from baseline to follow-up, being significant for the HF spectral component (p=0.03).ConclusionAmong cleaners, a worksite aerobic exercise intervention improved cardiac autonomic regulation during work and leisure, but not during sleep. The health effect of this contrasting change in autonomic regulation needs further investigation.
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| 12. |
- Krustrup, Peter, et al.
(författare)
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Neuromuscular blockade of slow twitch muscle fibres elevates muscle oxygen uptake and energy turnover during submaximal exercise in humans.
- 2008
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Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 586:Pt 24, s. 6037-48
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Tidskriftsartikel (refereegranskat)abstract
- We tested the hypothesis that a greater activation of fast-twitch (FT) fibres during dynamic exercise leads to a higher muscle oxygen uptake (VO2 ) and energy turnover as well as a slower muscle on-kinetics. Subjects performed one-legged knee-extensor exercise for 10 min at an intensity of 30 W without (CON) and with (CUR) arterial injections of the non-depolarizing neuromuscular blocking agent cisatracurium. In CUR, creatine phosphate (CP) was unaltered in slow twitch (ST) fibres and decreased (P < 0.05) by 28% in FT fibres, whereas in CON, CP decreased (P < 0.05) by 33% and 23% in ST and FT fibres, respectively. From 127 s of exercise, muscle VO2 was higher (P < 0.05) in CUR compared to CON (425 +/- 25 (+/- S.E.M.) versus 332 +/- 30 ml min(-1)) and remained higher (P < 0.05) throughout exercise. Using monoexponential fitting, the time constant of the exercise-induced muscle VO2 response was slower (P < 0.05) in CUR than in CON (55 +/- 6 versus 33 +/- 5 s). During CUR and CON, muscle homogenate CP was lowered (P < 0.05) by 32 and 35%, respectively, and also muscle lactate production was similar in CUR and CON (37.8 +/- 4.1 versus 35.2 +/- 6.2 mmol). Estimated total muscle ATP turnover was 19% higher (P < 0.05) in CUR than in CON (1196 +/- 90 versus 1011 +/- 59 mmol) and true mechanical efficiency was lower (P < 0.05) in CUR than in CON (26.2 +/- 2.0 versus 30.9 +/- 1.5%). In conclusion, the present findings provide evidence that FT fibres are less efficient than ST fibres in vivo at a contraction frequency of 1 Hz, and that the muscle VO2 kinetics is slowed by FT fibre activation.
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| 13. |
- Krustrup, Peter, et al.
(författare)
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Recruitment of fibre types and quadriceps muscle portions during repeated, intense knee-extensor exercise in humans.
- 2004
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Ingår i: Pflügers Archiv. - : Springer Science and Business Media LLC. - 0031-6768 .- 1432-2013. ; 449:1, s. 56-65
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Tidskriftsartikel (refereegranskat)abstract
- To investigate recruitment of slow-twitch (ST) and fast-twitch (FT) muscle fibres, as well as the involvement of the various quadriceps femoris muscle portions during repeated, intense, one-legged knee-extensor exercise, 12 healthy male subjects performed two 3-min exercise bouts at approximately 110% maximum thigh O2 consumption (EX1 and EX2) separated by 6 min rest. Single-fibre metabolites were determined in successive muscle biopsies obtained from the vastus lateralis muscle (n = 6) and intra-muscular temperatures were continuously measured at six quadriceps muscle sites (n = 6). Creatine phosphate (CP) had decreased (P < 0.05) by 27, 73 and 88% in ST fibres and 25, 71 and 89% in FT fibres after 15 and 180 s of EX1 and after 180 s of EX2, respectively. CP was below resting mean-1 SD in 15, 46, 84 and 100% of the ST fibres and 9, 48, 85 and 100% of the FT fibres at rest, after 15 and 180 s of EX1 and after 180 s of EX2, respectively. A significant muscle temperature increase (deltaTm) occurred within 2-4 s at all quadriceps muscle sites. DeltaTm varied less than 10% between sites during EX1, but was 23% higher (P < 0.05) in the vastus lateralis than in the rectus femoris muscle during EX2. DeltaTm in the vastus lateralis was 101 and 109% of the mean quadriceps value during EX1 and EX2, respectively. We conclude that both fibre types and all quadriceps muscle portions are recruited at the onset of intense knee-extensor exercise, that essentially all quadriceps muscle fibres are activated during repeated intense exercise and that metabolic measurements in the vastus lateralis muscle provide a good indication of the whole-quadriceps muscle metabolism during repeated, intense, one-legged knee-extensor exercise.
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| 14. |
- Krustrup, Peter, et al.
(författare)
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Slow-twitch fiber glycogen depletion elevates moderate-exercise fast-twitch fiber activity and O2 uptake.
- 2004
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Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 36:6, s. 973-82
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: We tested the hypotheses that previous glycogen depletion of slow-twitch (ST) fibers enhances recruitment of fast-twitch (FT) fibers, elevates energy requirement, and results in a slow component of VO2 during moderate-intensity dynamic exercise in humans. METHODS: Twelve healthy, male subjects cycled for 20 min at approximately 50% VO2max with normal glycogen stores (CON) and with exercise-induced glycogen depleted ST fibers (CHO-DEP). Pulmonary VO2 was measured continuously and single fiber, muscle homogenate, and blood metabolites were determined repeatedly during each trial. RESULTS: ST fiber glycogen content decreased (P < 0.05) during CON (293 +/- 24 to 204 +/- 17 mmol x kg d.w.), but not during CHO-DEP (92 +/- 22 and 84 +/- 13 mmol x kg d.w.). FT fiber CP and glycogen levels were unaltered during CON, whereas FT fiber CP levels decreased (29 +/- 7%, P < 0.05) during CHO-DEP and glycogen content tended to decrease (32 +/- 14%, P = 0.07). During CHO-DEP, VO2 was higher (P < 0.05) from 2 to 20 min than in CON (0-20 min:7 +/- 1%). Muscle lactate, pH and temperature, ventilation, and plasma epinephrine were not different between trials. From 3 to 20 min of CHO-DEP, VO2 increased (P <0.05) by 5 +/- 1% from 1.95 +/- 0.05 to 2.06 +/- 0.08 L x min but was unchanged during CON. In this exercise period, muscle pH and blood lactate were unaltered in both trials. Exponential modeling revealed a slow component of VO2 equivalent to 0.12 +/- 0.04 L x min during CHO-DEP. CONCLUSION: This study demonstrates that previous glycogen depletion of ST fibers enhances FT fiber recruitment, elevates O2 cost, and causes a slow component of VO2 during dynamic exercise with no blood lactate accumulation or muscular acidosis. These findings suggest that FT fiber recruitment elevates energy requirement of dynamic exercise in humans and support an important role of active FT fibers in producing the slow component of VO2
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| 15. |
- Krustrup, Peter, et al.
(författare)
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The slow component of oxygen uptake during intense, sub-maximal exercise in man is associated with additional fibre recruitment.
- 2004
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Ingår i: Pflügers Archiv. - : Springer Science and Business Media LLC. - 0031-6768 .- 1432-2013. ; 447:6, s. 855-66
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Tidskriftsartikel (refereegranskat)abstract
- Single muscle fibre metabolites and pulmonary oxygen uptake (VO2) were measured during moderate and intense, sub-maximal exercise to test the hypothesis that additional fibre recruitment is associated with the slow component of VO2. Seven healthy, male subjects performed 20 min moderate (MOD, approximately 50% of VO(2,max)) and intense (INT, approximately 80% VO(2,max)) cycling at 70 rpm. Glycogen content decreased significantly in type I and IIa fibres during INT, but only in type I fibres during MOD. During INT, creatine phosphate (CP) content decreased significantly both in types I and II fibres in the first 3 min (DeltaCP: 16.0+/-2.7 and 16.8+/-4.7 mmol kg(-1) d.w., respectively) and in the next 3 min (DeltaCP: 16.2+/-4.9 and 25.7+/-6.7 mmol kg(-1) d.w., respectively) with no further change from 6-20 min. CP content was below the pre-exercise level (mean-1 SD) in 11, 37, 70 and 74% of the type I fibres after 0, 3, 6 and 20 min of INT, respectively, and in 13, 45, 83 and 74% of the type II fibres. During INT, VO2 increased significantly by 6+/-1 and 4+/-1% in the periods 3-6 and 6-20 min, respectively (Delta VO(2,(6-3 min)): 0.14+/-0.02 l min(-1)), whereas VO2 was unchanged from 3 to 20 min of MOD. Exponential fitting revealed a slow component of VO2 during INT that appeared after approximately 2.6 min and amounted to 0.24 l min(-1). The present study demonstrates that additional type I and II fibres are recruited with time during intense sub-maximal exercise in temporal association with a significant slow component of VO2.
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| 16. |
- Lind, Rune Rasmussen, et al.
(författare)
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Acute high-intensity football games can improve children's inhibitory control and neurophysiological measures of attention
- 2019
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - Chichester : Wiley-Blackwell Publishing Inc.. - 0905-7188 .- 1600-0838. ; 29:10, s. 1546-1562
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies suggest that a single bout of exercise can lead to transient performance improvements in specific cognitive domains in children. However, more knowledge is needed to determine the key exercise characteristics for obtaining these effects and how they translate into real-world settings. In the present study, we investigate how small-sided football games of either high-or moderate-intensity affect measures of inhibitory control in a school setting. Eighty-one children (mean age 11.8, 48 boys) were randomly allocated to three groups performing 20-minute of high-intensity small-sided real football games (SRF), moderate-intensity small-sided walking football games (SWF) or resting (RF). Behavioral measures of inhibitory control and neurophysiological measures of attention (P300 latency and amplitude) were obtained during a flanker task performed at baseline and 20 minutes following the intervention. Retention of declarative memory was assessed in a visual memory task 7 days after the intervention. Measures of inhibitory control improved more in children performing SRF compared to SWF 19 ms, 95% CI [7, 31 ms] (P = 0.041). This was paralleled by larger increases in P300 amplitudes at Fz in children performing SRF compared both to RF in congruent (3.54 mu V, 95% CI [0.85, 6.23 mu V], P = 0.039) and incongruent trials (5.56 mu V, 95% CI [2.87, 8.25 mu V], P < 0.001) and compared to SWF in incongruent trials (4.10 mu V, 95% CI [1.41, 6.68 mu V], P = 0.010). No effects were found in measures of declarative memory. Together this indicates that acute high-intensity small-sided football games can transiently improve measures of inhibitory control and neurophysiological correlates of attention. Intense small-sided football games are easily implementable and can be employed by practitioners, for example, during breaks throughout the school day. © 2019 The Authors. Scandinavian Journal of Medicine & Science In Sports Published by John Wiley & Sons Ltd.
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| 17. |
- Lindberg, Ann-Sofie, 1972-
(författare)
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Firefighters' physical work capacity
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to identify valid, simple, and inexpensive physical tests that can be used for evaluation of firefighters’ physical work capacity. Paper I included fulltime- and part-time firefighters (n = 193), aged 20-60 years. Perceived physical demands of firefighting work tasks were ranked, and comparisons between subject groups rating were done with the Mann Whitney U-test and Binominal test. Papers II and III included male firefighters and civilian men and women (n = 38), aged 24-57 years. Laboratory and field tests of aerobic fitness, muscle strength and endurance, balance, and simulated firefighting work tasks were performed. Physical capacity comparisons between subject groups were done and bivariate correlations between physical tests and work capacity in the simulated firefighting work tasks analyzed. Paper IV included the same subjects as in Paper II-III (training-set), and additional 90 subjects (prediction-set), aged 20-50 years. Laboratory and field tests of aerobic fitness, muscle strength and endurance and balance, and simulated firefighting work tasks were included. Data from the training-set was used to build models for prediction of firefighters’ physical work capacity, using multivariate statistic. The prediction-set was used to externally validate the selected models. Several work tasks were rated as physically demanding and significant differences (p < 0.05) in ratings were found between full-time and part-time firefighters (Paper I). Significant differences were found between subject groups in physical capacity, and work capacity (p < 0.01) (Paper II-IV). Both laboratory and field tests were significantly (p < 0.01) correlated with work capacity time (Paper II-III). The prediction (R2) and predictive power (Q2) of firefighters’ work capacity (Carrying hose baskets upstairs, Hose pulling, Demolition at or after a fire, Victim rescue, and Carrying hose baskets over terrain) was R2 = 0.74 to 0.91, and Q2 = 0.65 to 0.85, and the external validation ranged between R2: 0.38 to 0.80 (Paper IV).In conclusion, rowing 500 m (s), maximal handgrip strength (kg), endurance bench press (n), running 3000 m (s and s scaled to body weight) upright barbell row (n) and standing broad jump (m) together provides valid information about firefighters’ physical work capacity.
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| 18. |
- Madsen, Esben Elholm, et al.
(författare)
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Motivational predictors of children's involvement in out-of-school activities : An application of a football program
- 2023
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - Chichester : Wiley-Blackwell Publishing Inc.. - 0905-7188 .- 1600-0838. ; 33:1, s. 72-83
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Tidskriftsartikel (refereegranskat)abstract
- The “11 for Health in Denmark” in-school educational football program has shown to have numerous positive physiological and psychological effects in 10- to 12-year-old schoolchildren. A key part of the successful application of the program, however, has not yet been examined, namely the motivational processes underlying participation and behavioral changes. This study examined such motivational processes (i.e., autonomous motivation, beliefs, and intentions) using the trans-contextual model (TCM) and investigated if the 11 for Health in Denmark program increased intentions to participate in physical activity (PA) outside of school in 10- to 12-year-old schoolchildren. Using a web-based questionnaire, Danish-speaking schoolchildren (N = 276 [boys, 50.4%]; Mage = 10.44, SD = 0.35) from three schools and seven classes completed TCM-based questionnaires at three time-points (weeks 0, 1, and 5) while participating in the 11 for Health in Denmark program. Single-indicator structural equation modeling was performed to examine goodness-of-fit and parameter estimates. A path analysis using maximum likelihood estimation was used to test the direct and indirect effects of the TCM model. The results partly supported a mediation sequence, as we found significant direct effects in eight of 13 motivational variables (β = −0.25–0.83, p <0.05), indirect effects in one of nine variables (β = 0.15, p < 0.01), but no effects with regard to PA behavior. Findings provide evidence for a motivational link between Danish-speaking schoolchildren's autonomous and controlled motivation from in school to out of school, and may inform future interventions promoting motivation and participation in out of school PA. © 2022 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.
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| 19. |
- Madsen, Mads, et al.
(författare)
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The “11 for Health in Denmark” intervention in 10- to 12-year-old Danish girls and boys and its effects on well-being—A large-scale cluster RCT
- 2020
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - Chichester : Wiley-Blackwell Publishing Inc.. - 0905-7188 .- 1600-0838. ; 30:9, s. 1787-1795
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Tidskriftsartikel (refereegranskat)abstract
- Background: The present study investigates the well‐being effects for 10‐ to 12‐year‐old children who participated in the school‐based intervention “11 for Health in Denmark,” which comprises physical activity (PA) and health education. Subgroup analyses were carried out for boys and girls.Method: Three thousand sixty‐one children were randomly assigned to an intervention group (IG) or a control group (CG) by 5:1 cluster randomization by school. 2533 children (mean age 11.5 ± 0.4; 49.7% boys) were assigned to IG and 528 children (mean age 11.4 ± 0.5; 50.8% boys) were assigned to CG. IG participated in the “11 for Health in Denmark” 11‐week program, consisting of 2 × 45 min per week of football drills, small‐sided games, and health education. CG did not participate in any intervention and continued with their regular education. Before and after the intervention period, both groups answered a shortened version of the multidimensional well‐being questionnaire KIDSCREEN‐27.Results: The “11 for Health in Denmark” intervention program had a positive effect on physical well‐being in girls (IG: 48.6 ± 8.5 to 50.2 ± 9.3), whereas the improvement was not significant in boys. The program also had a positive impact on well‐being scores for peers and social support (IG: 50.2 ± 10.2 to 50.8 ± 10.1), though when analyzed separately in the subgroups of boys and girls the changes were not significant. No between‐group differences were found for psychological well‐being or school environment.Conclusion: The intervention program had a positive between‐group effect on physical well‐being in girls, whereas the change was not significant in boys. The overall scores for peers and social support improved during the intervention period, but no subgroup differences were found. © 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
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| 20. |
- Madsen, Mads, et al.
(författare)
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Well-Being, Physical Fitness, and Health Profile of 2,203 Danish Girls Aged 10-12 in Relation to Leisure-time Sports Club Activity-With Special Emphasis on the Five Most Popular Sports
- 2022
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Ingår i: Strength and conditioning journal. - Philadelphia, PA : Lippincott Williams & Wilkins. - 1524-1602 .- 1533-4295. ; 36:8, s. 2283-2290
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the relationship between leisure-time sports club activities and well-being as well as physical health parameters in 10-12-year-old Danish girls. Two thousand two hundred three girls took part in the study, which included questionnaires on participation in leisure-time sports clubs, well-being, Yo-Yo intermittent recovery level 1 children's test, long jump, balance tests, body composition, blood pressure (BP), and resting heart rate (RHR). Data were analyzed according to whether the girls participated in leisure-time sport and according to the 5 most frequently reported sports. Girls enrolled in leisure-time sports had higher physical well-being (49.3 ± 8.6 vs. 45.2 ± 8.3), psychological well-being (50.4 ± 9.0 vs. 49.4 ± 9.8), experienced more peer and social support (50.2 ± 10.0 vs. 48.9 ± 10.7), and perceived a more positive school environment (52.5 ± 8.0 vs. 50.5 ± 9.3), as well as showing higher Yo-Yo (+39%), long jump (+10%), and balance performance (+15%) than girls not involved in sport clubs. The girls active in sports clubs had higher relative muscle mass (+5%), lower fat percentage (-11%), body mass index (-5%), RHR (-3.4 b·min-1), and diastolic BP (-1.4 mm Hg) compared with girls not involved in sport (p<0.05). Girls who played soccer showed higher aerobic fitness compared with inactive girls (+67%), dancers (+39%), swimmers (+38%), and gymnasts (+16%). Gymnasts had a lower fat percentage than inactive girls (-19%), team handballers (-10%), swimmers (-12%), and soccer players (-4%). Girls participating in club-based leisure-time sports showed higher well-being and better fitness and health profiles than girls not involved in any sports club activities. Girls involved in soccer had better aerobic fitness and gymnasts a lower fat percentage. Copyright © 2020 National Strength and Conditioning Association.
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