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Effects of Hypoxia Severity on Muscle Oxygenation Kinetics Using Statistical Parametric Mapping During Repeated Treadmill Sprints

Clint Hansen, Franck Brocherie, Grégoire P. Millet, and Olivier Girard

Purpose: We examined the effects of increasing hypoxia severity on oxygenation kinetics in the vastus lateralis muscle during repeated treadmill sprints, using statistical parametric mapping (SPM). Methods: Ten physically active males completed 8 sprints of 5 seconds each (recovery = 25 s) on a motorized sprint treadmill in normoxia (sea level; inspired oxygen fraction = 0.21), moderate hypoxia (inspired oxygen fraction = 0.17), and severe hypoxia (SH; inspired oxygen fraction = 0.13). Continuous assessment of tissue saturation index (TSI) in the vastus lateralis muscle was conducted using near-infrared spectroscopy. Subsequently, TSI data were averaged for the sprint–recovery cycle of all sprints and compared between conditions. Results: The SPM analysis revealed no discernible difference in TSI signal amplitude between conditions during the actual 5-second sprint phase. However, during the latter portion of the 25-second recovery phase, TSI values were lower in SH compared with both sea level (from 22 to 30 s; P = .003) and moderate hypoxia (from 16 to 30 s; P = .001). The mean distance covered at sea level (22.9 [1.0] m) was greater than for both moderate hypoxia (22.5 [1.2] m; P = .045) and SH (22.3 [1.4] m; P = .043). Conclusions: The application of SPM demonstrated that only SH reduced muscle oxygenation levels during the late portion of the passive (recovery) phase and not the active (sprint) phase during repeated treadmill sprints. These findings underscore the usefulness of SPM for assessing muscle oxygenation differences due to hypoxic exposure and the importance of the duration of the between-sprints recovery period.

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Training Regimen of an Elite Ultramarathon Runner: A Case Study of What Led Up to the 24-Hour World-Record Run

Jonathan Byrne, Sarah Lynch, and G. Monique Mokha

Purpose: Ultramarathon running has gained popularity over several decades. Although there has been considerable research on training for other running events, from the 100-m to the marathon at 26.2 miles (42.2 km), there is little evidence on best practices for ultramarathons, where distances potentially exceed 100 miles (160.9 km). Methods: In this case study, we examine the training regimen of an elite ultramarathon runner who broke 8 world records in 2021 and 2022, including the 24-hour run in which he ran 319.6 km in September 2022. Training data from December 28, 2020, to September 17, 2022, were collected from the Strava application database (recorded on Coros watch) and analyzed using Microsoft Excel and Tableau. Results: Our subject completed 5 training blocks, with volume per training block averaging 172.1 to 263 km/wk. Peak running volume per training block occurred on average 3.2 weeks out from races and reached a maximum of 378 km/wk. Recovery was emphasized the week following a race, with less running (19 km/wk) and more cross-training. Interval-type workouts (1- to 10-km repeats) were completed throughout training blocks. The average pace during the 24-hour world-record run was 4 minutes and 30 seconds per kilometer (4:30/km), closely matching the overall average training pace. Conclusions: These findings suggest that training for ultramarathon races should include high-volume running at varied paces and intensity with cross-training to avoid injuries. We hope that this evidence helps athletes understand how to prepare for these ultraendurance events.

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The Dose–Response in Elite Soccer: Preliminary Insights From Menstrual-Cycle Tracking During the FIFA Women’s World Cup 2019

Dawn Scott, Georgie Bruinvels, Dean Norris, and Ric Lovell

Purpose: This preliminary study examined the influence of estimated menstrual-cycle (MC) phase on responses to soccer matches and training sessions in preparation for and during the FIFA (Fédération internationale de football association) Women’s World Cup 2019. Methods: Twenty outfield players representing a national team were tracked over a 45-day period. External (10-Hz global positioning system; total and distance covered at high-metabolic power [≥20 W·kg−1]) and internal load measures (minutes ≥80% heart-rate maximum, sessional ratings of perceived exertion) were collected during all training and matches, with single-item wellness measures (fatigue, soreness, sleep quality, and sleep duration) collected each morning prior to activity. MC phase was estimated individually via an algorithm, informed from pretournament survey responses and ongoing symptom reporting (FitrWoman). Model comparison statistics were used to determine the impact of estimated MC phase in nonhormonal contraceptive users (n = 16). Results: Sessional rating of perceived exertion responses to total distances ≥5 km were higher during the luteal phase (+0.6–1.0 au; P ≤ .0178) versus menstruation (phase 1), but no other observable dose–response trends were observed. Sleep, fatigue, and soreness ratings were not typically associated with MC phase, with the exception of exacerbated fatigue ratings in luteal versus follicular phase 48 hours postmatch (−0.73 au, P = .0275). Conclusions: Preliminary findings suggest that estimated MC phase may contribute to the understanding of the dose–response to soccer training and matches.

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Variability of External Load Measures During Soccer Match Play: Influence of Player Fitness or Pacing?

Alireza Rabbani, Giorgios Ermidis, Filipe Manuel Clemente, and Craig Twist

Purpose: The aims of this study were to examine the variability of selected external load metrics within 15-minute intervals during soccer match play and examine their relationship with players’ high-intensity intermittent fitness. Methods: A total of 18 male soccer players were monitored for their external load metrics during 26 matches, which included total distance, high-metabolic-load distance, and mechanical work (defined as the sum of accelerations and decelerations >3 m2). Additionally, players completed the 30-15 Intermittent Fitness Test. Results: Total distance had lower coefficients of variation than high-metabolic-load distance and mechanical work (effect size [ES]: 5.2 to 6.4; very large). Within-player Δ-15min showed moderate to large decreases (ES: −0.7 to −1.6) and increases (ES: 0.9 to 1.8) in absolute and coefficient-of-variation values, respectively. Large relationships (r = .55 to .61) were observed between the Intermittent Fitness Test and 15-minmean and 15-minbest in all selected external load metrics. However, small to moderate (0.27 to 0.41) associations were observed between the Intermittent Fitness Test and Δ-15min in selected external load metrics. Conclusions: These findings suggest that players with relatively lower intermittent running capacity might show lower variability during matches, as evidenced by smaller reductions in high-intensity actions during the final 15 minutes. We attribute these observations to players’ possessing better pacing strategies.

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Effect of the Fran CrossFit Workout on Oxygen Uptake Kinetics, Energetics, and Postexercise Muscle Function in Trained CrossFitters

Manoel Rios, Klaus Magno Becker, Ana Sofia Monteiro, Pedro Fonseca, David B. Pyne, Victor Machado Reis, Daniel Moreira-Gonçalves, and Ricardo J. Fernandes

Purpose: Fran is one of the most popular CrossFit benchmark workouts used to control CrossFitters’ improvements. Detailed physiological characterization of Fran is needed for a more specific evaluation of CrossFitters’ training performance improvements. The aim of the study was to analyze the oxygen uptake ( V ˙ O 2 ) kinetics and characterize the energy system contributions and the degree of postexercise fatigue of the unbroken Fran. Methods: Twenty trained CrossFitters performed Fran at maximal exertion. V ˙ O 2 and heart-rate kinetics were assessed at baseline and during and post-Fran. Blood lactate and glucose concentrations and muscular fatigue were measured at baseline and in the recovery period. Results: A marked increase in V ˙ O 2 kinetics was observed at the beginning of Fran, remaining elevated until the end ( V ˙ O 2 peak : 49.2 [3.7] mL·kg−1·min−1, V ˙ O 2 amplitude: 35.8 [5.2] mL·kg−1·min−1, time delay: 4.7 [2.5] s and time constant: 23.7 [11.1] s; mean [SD]). Aerobic, anaerobic lactic, and alactic pathways accounted for 62% (4%), 26% (4%), and 12% (2%) of energy contribution. Reduction in muscle function in jumping ability (jump height: 8% [6%], peak force: 6% [4%], and maximum velocity: 4% [2%]) and plank prone test (46% [20%]) was observed in the recovery period. Conclusions: The Fran unbroken workout is a high-intensity effort associated with an elevated metabolic response. This pattern of energy response highlights the primary contribution of aerobic energy metabolism, even during short and very intense CrossFit workouts, and that recovery can take >24 hours due to cumulative fatigue.

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Effect of Wetsuit Use on Body Temperature and Swimming Performance During Training in the Pool: Recommendations for Open-Water Swimming Training With Wetsuits

Tomomi Fujimoto, Yuiko Matsuura, Yasuhiro Baba, and Reira Hara

Purpose: Open-water swimmers need to train with wetsuits to get familiar with them; however, body core temperature (T core) kinetics when using wetsuits in swimming-pool training remains unclear. The present study assessed the effects of wetsuit use in pool training on T core, subjective perceptions, and swimming performance to obtain suggestions for wearing wetsuits in training situations. Methods: Four elite/international-level Japanese swimmers (2 female, age 24 [1] y) completed two 10-km trials with (WS) and without wetsuit (SS) in the swimming pool (T w: 29.0 °C). During the trial, swimmers were allowed to remove their wetsuit if they could no longer tolerate the heat. T core was continuously recorded via ingestible temperature sensors. Swimming speed was estimated from every 100-m lap time. Results: T core increased by distance in both trials in all swimmers. T core when swimmers removed their wetsuit in the WS (distance: 3800 [245] m, time: 2744 [247] s) was higher than that at the same distance in the SS in all swimmers. Rating of perceived exertion was higher in the SS than the WS, and swimming speed was slower in the WS than the SS in all swimmers. Conclusion: Wetsuit use during pool training increases T core and decreases swimming performance. Although wearing wetsuits in training situations is important for familiarization, for the safety of the swimmers, it is recommended that they remove their wetsuit if they feel too hot.

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Acute Responses to Repeated-Sprint Training in Hypoxia Combined With Whole-Body Cryotherapy: A Preliminary Study

Thibaud Mihailovic, Alain Groslambert, Romain Bouzigon, Simon Feaud, Grégoire P. Millet, and Philippe Gimenez

Purpose: This study aimed to investigate acute psychophysiological responses to repeated-sprint training in hypoxia (RSH) combined with whole-body cryotherapy (WBC). Method: Sixteen trained cyclists performed 3 sessions in randomized order: RSH, WBC-RSH (WBC pre-RSH), and RSH-WBC (WBC post-RSH). RSH consisted of 3 sets of 5 × 10-second sprints with 20-second recovery at a simulated altitude of 3000 m. Power output, muscle oxygenation (tissue saturation index), heart-rate variability, and recovery perception were analyzed. Sleep quality was assessed on the nights following test sessions and compared with a control night using nocturnal ActiGraphy and heart-rate variability. Results: Power output did not differ between the conditions (P = .27), while the decrease in tissue saturation index was reduced for WBC-RSH compared to RSH-WBC in the last set. In both conditions with WBC, the recovery perception was higher compared to RSH (WBC-RSH: +15.4%, and RSH-WBC: +21.9%, P < .05). The number of movements during the RSH-WBC night was significantly lower than for the control night (−18.7%, P < .01) and WBC-RSH (−14.9%, P < .05). RSH led to a higher root mean square of the successive differences of R-R intervals and high-frequency band during the first hour of sleep compared to the control night (P < .05) and RSH-WBC (P < .01). Conclusions: Inclusion of WBC in an RSH session did not modify the power output but could improve prolonged performance in hypoxia by maintaining muscle oxygenation. A single RSH session did not deteriorate sleep quality. WBC, particularly when performed after RSH, positively influenced recovery perception and sleep.

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Quantifying Offense and Defense Workloads in Professional Rugby Union

Luke J. Stevens, Will G. Hopkins, Jessica A. Chittenden, Bianca Z. Koper, and Tiaki Brett Smith

Purpose: Rugby union is a contact team sport demanding high levels of physical capacity, and understanding the match workloads can be useful to inform training. In this study, the factors influencing locomotion and contact workloads for offensive and defensive ball-in-play periods are quantified. Methods: Locomotion and contact metrics were collected from global positioning system units and videos for 31 professional players of a Super Rugby team across 14 games in the 2021 season. Data were analyzed with a generalized mixed-model procedure that included effects for type of play, playing position, match outcome, and ball-in-play time. Magnitudes were assessed with standardization, and evidence for substantial magnitudes was derived from sampling uncertainty. Results: When offense was compared to defense, most metrics showed decisively substantial increases (small to moderate) for forwards and backs. There was decisive evidence that locomotion metrics were substantially lower (large differences) and contact metrics were higher (very large differences) when comparing forwards to backs on offense and defense. When winning was compared to losing, there was good evidence that forwards experienced small increases in overall workload on defense, and backs experienced a small increase in high-speed running and a moderate decrease in contacts on offense. Match-to-match changes associated with ball-in-play time, attributed to fatigue, were decisive (moderate to very large) across most metrics for forwards and backs in offense and defense. Conclusions: The increased locomotion and contact workloads in offensive periods and the differing physical requirements between positions and match outcomes for both types of play are novel findings that should aid practitioners in designing effective training.

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Addressing Circadian Disruptions in Visually Impaired Paralympic Athletes

Travis Anderson, William M. Adams, Geoffrey T. Burns, Eric G. Post, Sally Baumann, Emily Clark, Karen Cogan, and Jonathan T. Finnoff

Purpose: Transmeridian travel is common for elite athletes participating in competitions and training. However, this travel can lead to circadian misalignment wherein the internal biological clock becomes desynchronized with the light–dark cycle of the new environment, resulting in performance decrement and potential negative health consequences. Existing literature extensively discusses recommendations for managing jet lag, predominantly emphasizing light-based interventions to synchronize the internal clock with the anticipated time at the destination. Nevertheless, visually impaired (VI) athletes may lack photoreceptiveness, diminishing or nullifying the effectiveness of this therapy. Consequently, this invited commentary explores alternative strategies for addressing jet lag in VI athletes. Conclusions: VI athletes with light perception but reduced visual acuity or visual fields may still benefit from light interventions in managing jet lag. However, VI athletes lacking a conscious perception of light should rely on gradual shifts in behavioral factors, such as meal timing and exercise, to facilitate the entrainment of circadian rhythms to the destination time. Furthermore, interventions like melatonin supplementation may prove useful during and after travel. In addition, it is recommended that athlete guides adopt phase-forward or phase-back approaches to synchronize with the athlete, aiding in jet-lag management and optimizing performance.

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Effects of 4 Different Velocity-Based Resistance-Training Programming Models on Physical Performance

Javier Riscart-López, Juan Sánchez-Valdepeñas, Raúl Mora-Vela, Javier Caro-Ávalos, Lidia Sánchez-González, Miguel Sánchez-Moreno, Juan Antonio León-Prados, and Fernando Pareja-Blanco

Purpose: To examine the effects of 4 programming models (linear [LP], undulating [UP], reverse [RP], and constant [CP]) on physical performance. Methods: Forty-eight moderately strength-trained men were randomly assigned to LP, UP, RP, and CP groups according to their 1-repetition maximum (1RM) in the full-squat exercise (SQ) and followed an 8-week training intervention using the SQ and monitoring movement velocity for every repetition. All groups trained with similar mean relative intensity (65% 1RM), number of repetitions (240), sets (3), and interset recovery (4 min) throughout the training program. Pretraining and posttraining measurements included, in the SQ, 1RM load, the average velocity attained for all absolute loads common to pretests and posttests (AV), and the average velocity for loads that were moved faster (AV > 1) and slower (AV < 1) than 1 m·s−1 at pretraining tests. Moreover, countermovement jump height and 20-m running sprint time were measured. Results: A significant time effect was found for all variables analyzed (P < .05), except for 20-m running sprint time. Significant group × time interactions were observed for 1RM, AV > 1, and AV (P < .05). After training, all groups attained significant strength gains on 1RM, AV, AV > 1, and AV < 1 (P < .001–.01). LP and RP groups improved their countermovement jump height (P < .01), but no significant changes were observed for UP and CP. No significant improvements were achieved in 20-m running sprint time for any groups. Conclusions: These different programming models are all suitable for improving physical performance. LP and RP induce similar or greater gains in physical performance than UP and CP.