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Franck Brocherie, Grégoire P. Millet, and Olivier Girard

Purpose:

To compare psychophysiological responses to 6 repeated-sprint sessions in normobaric hypoxia (RSH) and normoxia (RSN) in team-sport athletes during a 2-wk “live high–train low” training camp.

Methods:

While residing under normobaric hypoxia (≥14 h/d, FiO2 14.5–14.2%), 23 lowland elite field hockey players performed, in addition to their usual training, 6 sessions (4 × 5 × 5-s maximal sprints, 25-s passive recovery, 5 min rest) under either RSH (FiO2 ~14.5%) or RSN (FiO2 21%). Sprint 1 and 5 times, physiological strain (heart rate [HR], arterial oxyhemoglobin saturation [SpO2]), and perceptual responses (overall peripheral discomfort, difficulty breathing, and lower-limb discomfort) were monitored.

Results:

During the 1st session, HR increased across sets (P < .001) independently of the conditions, while SpO2 was globally lower (P < .001) for RSH (averaged value: 91.9% ± 1.2%) vs RSN (96.9% ± 0.6%). Thereafter, SpO2 and HR remained similar across sessions for each condition. While 1st-sprint time remained similar, last-sprint time and fatigue index significantly decreased across sets (P < .01) and sessions (P < .05) but not between conditions. Ratings of overall perceived discomfort, difficulty breathing, and lower-limb discomfort were higher (P < .05) in RSH vs RSN at the 1st session. During subsequent sessions, values for overall perceived discomfort (time [P < .001] and condition [P < .05] effects), difficulty breathing (time effect; P < .001), and lower-limb discomfort (condition [P < .001] and interaction [P < .05] effects) decreased to a larger extent in RSH vs RSN.

Conclusion:

Despite higher hypoxia-induced physiological and perceptual strain during the 1st session, perceptual responses improved thereafter in RSH so as not to differ from RSN. This indicates an effective acclimation and tolerance to this innovative training.

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Olivier Girard, Franck Brocherie, Jean-Benoit Morin, and Grégoire P. Millet

Purpose:

To determine the intrasession and intersession (ie, within- and between-days) reliability in treadmill sprinting-performance outcomes and associated running mechanics.

Methods:

After familiarization, 13 male recreational sportsmen (team- and racket-sport background) performed three 5-s sprints on an instrumented treadmill with 2 min recovery on 3 different days, 5–7 d apart. Intrasession (comparison of the 3 sprints of the first session) and intersession (comparison of the average of the 3 sprints across days) reliability of performance, kinetics, kinematics, and spring-mass variables were assessed by intraclass correlation coefficient (ICC) and coefficients of variation (CV%).

Results:

Intrasession reliability was high (ICC > .94 and CV < 8%). Intersession reliability was good for performance indices (.83 < ICC < .89 and CV < 10%, yet with larger variability for mean velocity than for distance covered or propulsive power) and kinetic parameters (ICC > .94 and CV < 5%, yet with larger variability for mean horizontal forces than for mean vertical forces) and ranged from good to high for all kinematic (.88 < ICC < .95 and CV ≤ 3.5%) and spring-mass variables (.86 < ICC < .99 and CV ≤ 6.5%). Compared with intrasession, minimal detectable differences were on average twice larger for intersession designs, except for sprint kinetics.

Conclusion:

Instrumented treadmill sprint offers a reliable method of assessing running mechanics during single sprints either within the same session or between days.

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Naoya Takei, Katsuyuki Kakinoki, Olivier Girard, and Hideo Hatta

Background: Training in hypoxia versus normoxia often induces larger physiological adaptations, while this does not always translate into additional performance benefits. A possible explanation is a reduced oxygen flux, negatively affecting training intensity and/or volume (decreasing training stimulus). Repeated Wingates (RW) in normoxia is an efficient training strategy for improving both physiological parameters and exercise capacity. However, it remains unclear whether the addition of hypoxia has a detrimental effect on RW performance. Purpose: To test the hypothesis that acute moderate hypoxia exposure has no detrimental effect on RW, while both metabolic and perceptual responses would be slightly higher. Methods: On separate days, 7 male university sprinters performed 3 × 30-s Wingate efforts with 4.5-min passive recovery in either hypoxia (FiO2: 0.145) or normoxia (FiO2: 0.209). Arterial oxygen saturation was assessed before the first Wingate effort, while blood lactate concentration and ratings of perceived exertion were measured after each bout. Results: Mean (P = .92) and peak (P = .63) power outputs, total work (P = .98), and the percentage decrement score (P = .25) were similar between conditions. Arterial oxygen saturation was significantly lower in hypoxia versus normoxia (92.0% [2.8%] vs 98.1% [0.4%], P < .01), whereas blood lactate concentration (P = .78) and ratings of perceived exertion (P = .51) did not differ between conditions. Conclusion: In sprinters, acute exposure to moderate hypoxia had no detrimental effect on RW performance and associated metabolic and perceptual responses.

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Naoya Takei, Jacky Soo, Hideo Hatta, and Olivier Girard

Background: Compared with normoxia, repeated short (5–10 s) sprints (>10 efforts) with incomplete recovery (≤30 s) in hypoxia likely cause substantial performance reduction accompanied by larger metabolic disturbances and magnitude of neuromuscular fatigue. However, the effects of hypoxia on performance of repeated long (30 s) “all-out” efforts with near complete recovery (4.5 min) and resulting metabolic and neuromuscular adjustments remain unclear. Purpose: The intention was to compare acute performance, metabolic, and neuromuscular responses across repeated Wingates between hypoxia and normoxia. Methods: On separate visits, 6 male participants performed 4 × 30-second Wingate efforts with 4.5-minute recovery in either hypoxia (fraction of inspired oxygen: 0.145) or normoxia. Responses to exercise (muscle and arterial oxygenation trends, heart rate, and blood lactate concentration) and the integrity of neuromuscular function in the knee extensors were assessed for each exercise bout. Results: Mean (P = .80) and peak (P = .92) power outputs, muscle oxygenation (P = .88), blood lactate concentration (P = .72), and perceptual responses (all Ps > .05) were not different between conditions. Arterial oxygen saturation was significantly lower, and heart rate higher, in hypoxia versus normoxia (P < .001). Maximal voluntary contraction force and peripheral fatigue indices (peak twitch force and doublets at low and high frequencies) decreased across efforts (all Ps < .001) irrespective of conditions (all Ps > .05). Conclusion: Despite heightened arterial hypoxemia and cardiovascular solicitation, hypoxic exposure during 4 repeated 30-second Wingate efforts had no effect on performance and accompanying metabolic and neuromuscular adjustments.

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Carl James, Aishwar Dhawan, Timothy Jones, and Olivier Girard

Purpose: To quantify the demands of specific on- and off-court sessions, using internal and external training load metrics, in elite squash. Methods: A total of 15 professional squash players (11 males and 4 females) wore a 100-Hz triaxial accelerometer/global positioning system unit and heart rate monitor during on-court “Group,” “Feeding,” “Ghosting,” “Matchplay,” and off-court “Conditioning” sessions across a 2-week in-season microcycle. Comparisons of absolute training load (total values) and relative intensity (per minute) were made between sessions for internal (session rating of perceived exertion, differential rating of perceived exertion, TRIMP) and external (Playerload, very high–intensity movements [>3.5 m·s−2]) metrics. Results: The Group sessions were the longest (79 [12] min), followed by Feeding (55 [15] min), Matchplay (46 [17] min), Conditioning (37 [9] min), and Ghosting (35 [6] min). Time >90% maximum heart rate was the lowest during Feeding (vs all others P < .05) but other sessions were not different (all P > .05). Relative Playerload during Conditioning (14.3 [3.3] arbitrary unit [a.u.] per min, all P < .05) was higher than Ghosting (7.5 [1.2] a.u./min) and Matchplay (6.9 [1.5] a.u./min), with no difference between these 2 sessions (P ≥ .999). Conditioning produced the highest Playerloads (519 [153] a.u., all P < .001), with the highest on-court Playerloads from Group (450 [94] a.u., all P < .001). The highest session rating of perceived exertion (all P < .001), Edward’s TRIMP (all P < .001), and TEAM-TRIMP (all P < .019) occurred during the Group sessions. Conclusions: Squash Matchplay does not systematically produce the highest training intensities and loads. Group sessions provide the highest training loads for many internal and external parameters and, therefore, play a central role within the training process. These findings facilitate planning or adjustment of intensity, volume, and frequency of sessions to achieve desirable physical outcomes.

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Olivier Girard, Franck Brocherie, Jean-Benoit Morin, Francis Degache, and Grégoire P. Millet

We compared different approaches to analyze running mechanics alterations during repeated treadmill sprints. Thirteen active male athletes performed five 5-second sprints with 25 seconds of recovery on an instrumented treadmill. This approach allowed continuous measurement of running kinetics/kinematics and calculation of vertical and leg stiffness variables that were subsequently averaged over 3 distinct sections of the 5-second sprint (steps 2–5, 7–10, and 12–15) and for all steps (steps 2–15). Independently from the analyzed section, propulsive power and step frequency decreased with fatigue, while contact time and step length increased (P < .05). Except for step frequency, all mechanical variables varied (P < .05) across sprint sections. The only parameters that highly depend on running velocity (propulsive power and vertical stiffness) showed a significant interaction (P < .05) between the analyzed sections, with smaller magnitude of fatigue-induced change observed for steps 2–5. Considering all steps or only a few steps during early, middle, or late phases of 5-second sprints provides similar mechanical outcomes during repeated treadmill sprinting, although acceleration induces noticeable differences between the sections studied. Furthermore, quantifying mechanical alterations from the early acceleration phase may not be readily detectable, and is not recommended.

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Alice Wallett, Andrew McKune, David Pyne, David Bishop, Olivier Girard, Philo Saunders, and Julien Périard

Introduction: Athletes engaged in repeated-sprint training in the heat can be at an increased risk of gastrointestinal ischemia and damage in response to a redistribution of blood to working skeletal muscles and the skin. This study investigated the effects of repeated sprinting in hot and cool conditions on markers of gastrointestinal damage. Methods: Twenty-five, well-trained, nonheat acclimated male team-sport athletes completed a five-session, repeated-sprint training regimen over 7 days in either HOT (40 °C and 40% relative humidity [RH]) or COOL (20 °C and 40% RH) conditions. Participants underwent a 20-min warm-up and four sets of 5 × 6-s maximal cycling sprints, with 24-s rest and 5-min recovery between sets. Venous blood was collected pre-, post-, and 1 hr postexercise and analyzed for intestinal fatty acid binding protein, lipopolysaccharide binding protein, soluble CD14, and heat-shock protein. Results: Intestinal fatty acid binding protein concentrations were significantly increased (p < .004) postexercise (593 and 454 pg/ml) and 1 hr postexercise (466 and 410 pg/ml) on both Days 1 and 5 in HOT. Soluble CD14 increased by 398 and 308 ng/ml postexercise (p = .041), and lipopolysaccharide binding protein increased by 1,694 ng/ml postexercise on Day 1 in HOT (p < .05) and by 1,520 ng/ml on Day 5 in COOL (p = .026). Core and skin temperature, rating of perceived exertion, and thermal sensation were higher (p < .05) in HOT on Days 1 and 5 during sprinting. Conclusions: Repeated sprinting in the heat induced greater thermal strain and mild changes in gastrointestinal damage, likely attributable to the combination of environmental conditions and maximal-intensity exercise.

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Olivier Girard, Romain Leuenberger, Sarah J. Willis, Fabio Borrani, and Grégoire P. Millet

Purpose: The authors compared the effects of active preconditioning with local and systemic hypoxia during submaximal cycling. Methods: On separate visits, 14 active participants completed 4 trials. Each visit was composed of 1 preconditioning phase followed, after 40 minutes of rest, by 3 × 6-minute cycling bouts (intensity = 85% of critical power; rest = 6 min). The preconditioning phase consisted of 4 × 5-minute cycling bouts at 1.5 W·kg−1 (rest = 5 min) in 4 conditions: control (no occlusion and normoxia), blood flow restriction (60% of total occlusion), HYP (systemic hypoxia; inspired fraction of oxygen = 13.6%), and blood flow restriction + HYP (local and systemic hypoxia combined). Results: During the preconditioning phase, there were main effects of both systemic (all P < .014) and local hypoxia (all P ≤ .001) on heart rate, arterial oxygen saturation, leg discomfort, difficulty of breathing, and blood lactate concentration. Cardiorespiratory variables, gross efficiency, energy cost, and energy expenditure during the last minute of 6-minute cycling bouts did not differ between conditions (all P > .105). Conclusion: Local and systemic hypoxic stimuli, or a combination of both, during active preconditioning did not improve physiological responses such as cycling efficiency during subsequent submaximal cycling.

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Nathan D.W. Smith, Jeremiah J. Peiffer, Olivier Girard, and Brendan R. Scott

Purpose: This study compared training loads and internal:external load ratios from an aerobic interval session at the highest perceptually sustainable intensity with and without blood flow restriction (BFR). Methods: On separate days, 14 endurance cyclists/triathletes completed four 4-minute self-paced aerobic cycling intervals at their highest sustainable intensity, with and without BFR (60% of arterial occlusion pressure). Internal training load was quantified using 3 training impulses (TRIMP; Banister, Lucia, and Edwards) and sessional ratings of perceived exertion. External load was assessed using total work done (TWD). Training load ratios between all internal loads were calculated relative to TWD. Results: Lucia TRIMP was lower for the BFR compared with non-BFR session (49 [9] vs 53 [8] arbitrary units [au], P = .020, d z = −0.71). No between-conditions differences were observed for Banister TRIMP (P = .068), Edwards TRIMP (P = .072), and training load in sessional ratings of perceived exertion (P = .134). The TWD was lower for the BFR compared with non-BFR session (223 [52] vs 271 [58] kJ, P < .001, d z = −1.27). Ratios were greater for the BFR session compared with non-BFR for Lucia TRIMP:TWD (0.229 [0.056] vs 0.206 [0.056] au, P < .001, d z = 1.21), Edwards TRIMP:TWD (0.396 [0.105] vs 0.370 [0.088] au, P = .031, d z = 0.66), and training load in sessional ratings of perceived exertion:TWD (1.000 [0.266] vs 0.890 [0.275] au, P = .044, d z = 0.60), but not Banister TRIMP:TWD (P = .306). Conclusions: Practitioners should consider both internal and external loads when monitoring BFR exercise to ensure the demands are appropriately captured. These BFR-induced changes were reflected by the Lucia TRIMP:TWD and Edwards TRIMP:TWD ratio, which could be used to monitor aerobic BFR training loads. The Lucia TRIMP:TWD ratio likely represents BFR-induced changes more appropriately compared with ratios involving either Edwards or Banister TRIMP.

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Myles C. Dennis, Paul S.R. Goods, Martyn J. Binnie, Olivier Girard, Karen E. Wallman, Brian T. Dawson, and Peter Peeling

Purpose: This study aimed to assess the influence of graded air temperatures during repeated-sprint training in hypoxia (RSH) on performance and physiological responses. Methods: Ten well-trained athletes completed one familiarization and 4 experimental sessions at a simulated altitude of 3000 m (0.144 FIO2) above sea level. Air temperatures utilized across the 4 experimental sessions were 20°C, 25°C, 30°C, and 35°C (all 50% relative humidity). The participants performed 3 sets of 5 × 10 seconds “all-out” cycle sprints, with 20 seconds of active recovery between sprints and 5 minutes of active recovery between sets (recovery intensity = 120 W). Core temperature, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion, and thermal sensation were collected. Results: There were no differences between conditions for peak power, mean power, and total work in each set (P > .05). There were no condition × time interaction effects for any variables tested. The peak core temperature was highest at 30°C (38.06°C [0.31°C]). Overall, the pulse oxygen saturation was higher at 35°C than at 20°C (P < .001; d < 0.8), 25°C (P < .001; d = 1.12 ± 0.54, large), and 30°C (P < .001; d = 0.84 ± 0.53, large). Conclusion: Manipulating air temperature between 20°C and 35°C had no effect on performance or core temperature during a typical RSH session. However, the pulse oxygen saturation was preserved at 35°C, which may not be a desirable outcome for RSH interventions. The application of increased levels of ambient heat may require a different approach if augmenting the RSH stimulus is the desired outcome.