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- Björklund, Glenn, 1972-, et al.
(author)
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Biomechanical Adaptations and Performance Indicators in Short Trail Running
- 2019
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In: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 10
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Journal article (peer-reviewed)abstract
- Our aims were to measure anthropometric and oxygen uptake ((V)over dot O-2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 +/- 5 years; stature: 179.5 +/- 0.8 cm; body mass: 69.1 +/- 7.4 kg) performed laboratory tests to determine (V)over dot O-2 (max), running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 +/- 1:57 min vs. 21:08 +/- 2:09 min, P < 0.001), runners lost most time on the uphill sections and least on technical downhills (-2.5 +/- 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64 +/- 0.03 vs. 0.84 +/- 0.09 s; 0.26 +/- 0.03 vs. 0.46 +/- 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 +/- 46 vs. 175 +/- 24 Ns, P < 0.001) and related to GCT (r = 0.904, P < 0.001). Peak force was greater during downhill than during uphill running (1106 +/- 135 vs. 959 +/- 104 N, P < 0.01). Performance was related to absolute and relative (V)over dot O-2 (max) (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. (V)over dot O-2 (max), vertical running speed and fat percent are important predictors for trail running performance. Performance between runners varied the most on downhills throughout the course, while pacing resembled a reversed J pattern. Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.
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| 4. |
- Born, Dennis, et al.
(author)
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Near-Infrared Spectroscopy: More Accurate Than Heart Rate for Monitoring Intensity in Running in Hilly Terrain
- 2017
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In: International Journal of Sports Physiology and Performance. - : Human Kinetics. - 1555-0265 .- 1555-0273. ; 12:4, s. 440-447
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Journal article (peer-reviewed)abstract
- Purpose:To 1) investigate the cardiorespiratory and metabolic response of trail running and 2) evaluate whether heart rate (HR) adequately reflects the exercise intensity or whether the tissue saturation index (TSI) could provide a more accurate measure when running in hilly terrain.Methods:Seventeen competitive runners (female: n=4, V’O2max: 55±6 mL·kg−1·min−1; male: n=13, V’O2max: 68±6 mL·kg−1·min−1) performed a time trial on an off-road trail course. The course was made up of two laps covering a total distance of 7 km and included six steep up- and downhill sections with an elevation gain of 486 m. All runners were equipped with a portable breath-by-breath gas analyzer, HR belt, global positioning system receiver and near-infrared spectroscopy (NIRS) device to measure the TSI.Results:During the trail run, the exercise intensity within the uphill and downhill sections was 94±2% and 91±3% of HRmax, 84±8% and 68±7% of V’O2max, respectively. The oxygen uptake (V’O2) increased within the uphill and decreased within the downhill sections (P< .01). While HR was unaffected by the altering slope conditions, the TSI was inversely correlated to the changes in V’O2 (r = - .70, P< .05).Conclusions:The HR was unaffected by the continuously changing exercise intensity, however, the TSI reflected the alternations in V’O2. Recently used exclusively for scientific purpose, this NIRS based variable may offer a more accurate alternative to HR to monitor running intensity in the future, especially for training and competition in hilly terrain.
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- Jonsson Kårström, Malin, et al.
(author)
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Kinematical effects of rifle carriage on roller skiing in well-trained female and male biathletes
- 2023
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In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 33:4, s. 444-454
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Journal article (peer-reviewed)abstract
- Purpose: This study aimed to investigate how rifle carriage and skiing speed during biathlon roller skiing affect range of motion (ROM) in joint angles and equipment (skis and poles), the vertical distance between shoulders and treadmill (vertdist), as well as possible sex differences associated with rifle carriage. Methods: Fourteen biathletes (6 women, 8 men) roller-skied on a treadmill at submaximal and simulated race speeds, with (WR) and without (NR) a rifle, using gears 3 and 2. Kinematical data for the whole body, poles, roller-skis, rifle, and treadmill were monitored using a 3D motion capture system. Movements determined as flexion/extension (x), abduction/adduction (y), and/or internal/external rotation (z) were analyzed for the hip, shoulder, thorax, knee, ankle, elbow, poles, and roller skis. ROM (the difference between maximal and minimal angles) in joints and equipment, and vertdist were analyzed over six skiing cycles during each condition (WR and NR) and speed. Results: The maximal vertdist was lower for WR compared with NR (gear 3: 1.53 ± 0.06 vs 1.54 ± 0.06 m; gear 2: 1.49 ± 0.06 vs 1.51 ± 0.06 m; both p < 0.001). ROM in the upper body was altered when roller skiing WR (movements decreased in thorax and shoulder (x) and increased in elbow (only gear 3) (x), thorax (only gear 2), and shoulder (y) and (z); all p < 0.05) and increased with speed, without differences between sexes (p > 0.05). Conclusion: Since rifle carriage and speed appear to affect the kinematics of roller skiing, coaches, and biathletes are advised to perform skiing technique training under competition-like conditions (i.e., at race speeds while carrying the rifle).
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- Jonsson, Malin, et al.
(author)
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Biomechanical differences in double poling between sexes and level of performance during a classical cross-country skiing competition
- 2019
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In: Journal of Sports Sciences. - : Informa UK Limited. - 0264-0414 .- 1466-447X. ; 37:14, s. 1582-1590
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Journal article (peer-reviewed)abstract
- Biomechanical differences in double poling (DP) between sex and performance level were investigated in female and male cross-country skiers during a classical race (10/15 km). Skiers were divided into faster and slower on basis of race performance: females faster (n=20), females slower (n=20), males faster (n=20), and males slower (n=20). Based on video analysis while DP in a flat section of the track, joint and pole angles at pole plant (PP) and pole-off, cycle characteristics and the use and coordination pattern of heel-raise (raise of heels from the ground to have a higher body position at PP) were analysed. Faster females and males had 4.3% and 7.8% higher DP velocity than their slower counterparts (both P<0.001). Faster males had 6.5% longer cycles than slower males (P<0.001). Faster skiers stopped heel-raise later than slower skiers (females: 2.0±3.4% vs. −1.0±3.5%, P<0.05; males: 3.9±2.4% vs. 0.8±3.2% of cycle time in relation to PP, P<0.001). At PP, faster skiers and male skiers had a smaller pole angle and greater ankle to hip and ankle to shoulder angle with respect to vertical, resulting in a more distinct forward body lean. However, the majority of the differences are likely due to higher DP velocity.
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- Stöggl, Thomas, 1977-, et al.
(author)
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Biomechanical determinants of oxygen extraction during cross-country skiing
- 2013
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In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 23:1, s. e9-e20
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Journal article (peer-reviewed)abstract
- To determine the relationship of muscle activation, force production, and cycle characteristics to O2 extraction during high- and lower-intensity double poling (DP), nine well-trained male cross-country skiers performed DP on a treadmill for 3 min at 90% VO2peak followed by 6 min at 70%. During the final minute at each workload, arterial, femoral, and subclavian venous blood were collected for determination of partial pressure of O2, partial pressure of CO2, pH, and lactate. Electromyography (EMG) was recorded from six upper and lower body muscles, leg and pole forces were measured, and cardiorespiratory variables were monitored continuously. O2 extraction was associated with time point of peak pole force (PFpeak), duration of recovery, EMG activity, and lower body use. Arm O2 extraction was lower than in the legs at both intensities (P < 0.001) and was reduced to a lesser extent upon decreasing the workload (P < 0.05). Arm root-mean-square EMG was higher during the poling phase and entire cycle compared with the legs (P < 0.001). Blood lactate was higher in the subclavian than in femoral vein and artery (P < 0.001) and independent of intensity. O2 extraction was correlated to low muscle activation, later PFpeak, prolonged poling time, and extensive dynamic lower body use. Cycle rate and recovery time were associated with O2 extraction during high-intensity exercise only.
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| 8. |
- Stöggl, Thomas, 1977-, et al.
(author)
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High intensity interval training leads to greater improvements in acute heart rate recovery and anaerobic power as high volume low intensity training
- 2017
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In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 8
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Journal article (peer-reviewed)abstract
- The purpose of the current study was to explore if training regimes utilizing diverse training intensity distributions result in different responses on neuromuscular status, anaerobic capacity/power and acute heart rate recovery (HRR) in well-trained endurance athletes.Methods: Thirty-six male (n = 33) and female (n = 3) runners, cyclists, triathletes and cross-country skiers [peak oxygen uptake: (VO2peak): 61.9 ± 8.0 mL·kg−1·min−1] were randomly assigned to one of three groups (blocked high intensity interval training HIIT; polarized training POL; high volume low intensity oriented control group CG/HVLIT applying no HIIT). A maximal anaerobic running/cycling test (MART/MACT) was performed prior to and following a 9-week training period.Results: Only the HIIT group achieved improvements in peak power/velocity (+6.4%, P < 0.001) and peak lactate (P = 0.001) during the MART/MACT, while, unexpectedly, in none of the groups the performance at the established lactate concentrations (4, 6, 10 mmol·L−1) was changed (P > 0.05). Acute HRR was improved in HIIT (11.2%, P = 0.002) and POL (7.9%, P = 0.023) with no change in the HVLIT oriented control group.Conclusion: Only a training regime that includes a significant amount of HIIT improves the neuromuscular status, anaerobic power and the acute HRR in well-trained endurance athletes. A training regime that followed more a low and moderate intensity oriented model (CG/HVLIT) had no effect on any performance or HRR outcomes.
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| 10. |
- Swarén, Mikael, 1980-, et al.
(author)
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How do custom made insoles affect the pressure distribution under the feet in alpine skiing?
- 2016
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Conference paper (peer-reviewed)abstract
- Introduction Elite alpine skiers frequently adjust insoles, boots and skis to optimize skiing performance. There are numerous different constructions of custom made insoles. However, nobody has, to the authors’ knowledge, investigated the mechanisms behind a plausible performance increase. The purpose of the study was therefore to investigate the potential difference in pressure distribution under the feet when skiing with regular insoles compared to custom made insoles. Method A pre-study investigated differently constructed insoles and their possible effects on the pressure distribution under the feet. One test subject performed different squat and fly-wheel exercises with six differently constructed insoles. Kinetics and 3D-kinematics were collected to identify possible differences. One insole construction, with a flat bottom and a semi-soft upper layer, was thereafter chosen to be used for field tests. Nine professional skiers, including both race skiers and full time ski instructors, were recruited for the field tests. Each skier performed in a randomized order, three runs with a standard insole and three runs with a custom made insole. Plantar pressure under the feet was measured with the Pedar Mobile System at 100 Hz, for eight consecutive carving turns. The skiers were instructed to have the smallest possible time difference between all runs. The three runs for each situation were synchronized and the mean total, forefoot and midfoot pressure distributions were calculated. Results The pre-study results show that the pressure distribution between foot and insole and between insole and ski-boot depends on the insole construction. The mean time for all 54 runs was 26.62 ± 2.41 s and the mean individual time difference between the fastest and the slowest runs was 0.62 ± 0.33 s. All skiers showed large individual differences in percentage of “used” area under the feet, between the two types of insoles (5-80%). When skiing with the custom made insole, the total mean difference in percentage usage of the forefoot was -17 ± 19% and 8 ± 12% for the midfoot. Discussion The results show that the pressure distribution under the feet depends on the type of insole. However, the effect of a custom made insole is very individual. Hence, when performing studies of skiing kinetics and/or equipment, it is of vast importance that all subjects use similarly constructed custom made insoles. It can also be hypothesized that e.g., different canting angles of the ski-boot, affect the skier differently depending on the type of insole. Our suggestion is therefore to perform measurements to optimize the insoles before investigating and optimizing canting angles. The results also show that custom made insoles can assist the skier to utilize different areas of the foot. However, future studies are needed to investigate whether the decreased usage of the forefoot affects the overall aggressiveness of the setup and whether custom made insoles have a positive effect on skiing performance.
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