Franck Brocherie

Electrostimulation training effects on the physical performance of ice hockey players.

PURPOSE The aim of this study was to examine the influence of a short-term electromyostimulation (EMS) training program on the strength of knee extensors, skating, and vertical jump performance of a group of ice hockey players. METHODS Seventeen ice hockey players participated in this study, with nine in the electrostimulated group (ES) and the remaining height as controls (C). EMS sessions consisted of 30 contractions (4-s duration, 85 Hz) and were carried out 3x wk for 3 wk. Isokinetic strength of the knee extensor muscles was determined with a Biodex dynamometer at different eccentric and concentric angular velocities (angular velocities ranging from -120 to 300 degrees .s). Jumping ability was evaluated during squat jump (SJ), countermovement jump (CMJ), drop jump (DJ), and 15 consecutive CMJ (15J). Sprint times for 10- and 30-m skates in specific conditions were measured using an infrared photoelectric system. RESULTS After 3 wk of EMS training, isokinetic torque increased significantly (P<0.05) for ES group in eccentric (-120 and -60 degrees .s) and concentric conditions (60 and 300 degrees .s), whereas vertical jump height decreased significantly (P<0.05) for SJ (-2.9+/-2.4 cm), CMJ (-2.1+/-2.0 cm), and DJ (-1.3+/-1.1 cm). The 10-m skating performance was significantly improved (from 2.18+/-0.20 to 2.07+/-0.09 s, before and after the 3-wk EMS period, respectively; P<0.05). CONCLUSION It was demonstrated that an EMS program of the knee extensors significantly enhanced isokinetic strength (eccentric and for two concentric velocities) and short skating performance of a group of ice hockey players.

Hypoxic training and team sports: a challenge to traditional methods?

In 2007, Wilber1 presented the main altitude/hypoxic training methods used by elite athletes: ‘live high—train high’ (LHTH) and ‘live high—train low’ (LHTL); sleeping at altitude to gain the haematological adaptations (increased erythrocyte volume) but training at sea level to maximise performance (maintenance of sea-level training intensity and oxygen flux). The LHTL method can be accomplished through a number of methods and devices: natural/terrestrial altitude, nitrogen dilution, oxygen filtration and supplemental oxygen. Another method is the ‘live low—train high’ (LLTH) method including intermittent hypoxic exposure at rest (IHE) or during intermittent hypoxic training sessions (IHT). Noteworthy, all supporting references were conducted with endurance elite athletes (ie, cyclists, triathletes, cross-country skiers, runners, swimmers, kayakers and rowers) and there is an extensive literature relative to LHTH as well as LHTL. However, there is a lack of evidence for the applicability of these methods in team-sport athletes. In recent times, media reports have provided us with coverage of some high-profile clubs or national squads in various team-sport disciplines undertaking fitness programmes at altitude during the early preseason or in preparation of a major competition. Despite the evident observation that athletes from different team sports and from all around the world are using altitude training more than ever before, it is …

High-intensity Intermittent Training in Hypoxia: A Double-blinded, Placebo-controlled Field Study in Youth Football Players

Abstract Brocherie, F, Girard, O, Faiss, R, and Millet, GP. High-intensity intermittent training in hypoxia: A double-blinded, placebo-controlled field study in youth football players. J Strength Cond Res 29(1): 226–237, 2015—This study examined the effects of 5 weeks (∼60 minutes per training, 2 d·wk−1) of run-based high-intensity repeated-sprint ability (RSA) and explosive strength/agility/sprint training in either normobaric hypoxia repeated sprints in hypoxia (RSH; inspired oxygen fraction [FIO2] = 14.3%) or repeated sprints in normoxia (RSN; FIO2 = 21.0%) on physical performance in 16 highly trained, under-18 male footballers. For both RSH (n = 8) and RSN (n = 8) groups, lower-limb explosive power, sprinting (10–40 m) times, maximal aerobic speed, repeated-sprint (10 × 30 m, 30-s rest) and repeated-agility (RA) (6 × 20 m, 30-s rest) abilities were evaluated in normoxia before and after supervised training. Lower-limb explosive power (+6.5 ± 1.9% vs. +5.0 ± 7.6% for RSH and RSN, respectively; both p < 0.001) and performance during maximal sprinting increased (from −6.6 ± 2.2% vs. −4.3 ± 2.6% at 10 m to −1.7 ± 1.7% vs. −1.3 ± 2.3% at 40 m for RSH and RSN, respectively; p values ranging from <0.05 to <0.01) to a similar extent in RSH and RSN. Both groups improved best (−3.0 ± 1.7% vs. −2.3 ± 1.8%; both p ⩽ 0.05) and mean (−3.2 ± 1.7%, p < 0.01 vs. −1.9 ± 2.6%, p ⩽ 0.05 for RSH and RSN, respectively) repeated-sprint times, whereas sprint decrement did not change. Significant interactions effects (p ⩽ 0.05) between condition and time were found for RA ability–related parameters with very likely greater gains (p ⩽ 0.05) for RSH than RSN (initial sprint: 4.4 ± 1.9% vs. 2.0 ± 1.7% and cumulated times: 4.3 ± 0.6% vs. 2.4 ± 1.7%). Maximal aerobic speed remained unchanged throughout the protocol. In youth highly trained football players, the addition of 10 repeated-sprint training sessions performed in hypoxia vs. normoxia to their regular football practice over a 5-week in-season period was more efficient at enhancing RA ability (including direction changes), whereas it had no additional effect on improvements in lower-limb explosive power, maximal sprinting, and RSA performance.

Therapeutic Use of Exercising in Hypoxia: Promises and Limitations

It is well-established that different altitude training modalities can improve convective oxygen (O2) transport capacity and physical fitness of athletes (Millet et al., 2010). Exercising in hypoxia also induces specific muscular adaptations including increased oxidative enzymes (e.g., citrate synthase) activity, mitochondrial density, capillary-to-fiber ratio, and fiber cross-sectional area (Hoppeler et al., 2008). These changes with hypoxic training are mostly modulated via hypoxia-inducible factor 1α (HIF-1α) signaling cascade, which is not activated to the same extent when training is performed in normoxia or by passive hypoxic exposure. Indeed, large body of literature shows that, compared to hypoxic exercise, passive exposure to hypoxia does not provoke similar acute responses. In healthy individuals, both systemic (e.g., performance enhancement), cardiovascular (e.g., maximal O2 uptake, VO2max) or transcriptional muscular responses are minimal with intermittent passive exposures at moderate altitude. On the other hand, there are clear evidences that when hypoxia is combined with exercise, it triggers specific responses, not observed following similar exercise in normoxia (Bartsch et al., 2008; Lundby et al., 2009). In addition, greater specific adaptations have been reported in high-intensity vs. moderate-intensity hypoxic intervention (Faiss et al., 2013) (e.g., improvements in muscle O2 homeostasis and tissue perfusion induced by enhanced mitochondrial efficiency, control of mitochondrial respiration, angiogenesis, and muscle buffering capacity). It seems that the main underlying mechanism is the larger hypoxemia resulting from the combination of muscle deoxygenation (high-intensity exercise) and systemic desaturation (moderate hypoxia). In patients or elderly individuals, altitude is generally associated with increased health risks through enhanced sympathetic vasoconstrictor activation (Blitzer et al., 1996), obstructive sleep apneas (Nespoulet et al., 2012), hypoxemia (Levine et al., 1997), pulmonary hypertension (Valencia-Flores et al., 2004), arrhythmias (Kujanik et al., 2000), and alterations of postural control (Degache et al., 2012). However, several studies have investigated the therapeutic benefits of exercising in mild hypoxia on the blood pressure regulation and the influence of different hypoxic modalities in healthy individuals (Bailey et al., 2001; Wang et al., 2007; Haufe et al., 2008; Nishiwaki et al., 2011; Morishima et al., 2014; Shi et al., 2014) or in patients with different cardiovascular and respiratory risk factors such as chronic obstructive pulmonary disease (COPD) (Haider et al., 2009), obesity (Wiesner et al., 2010), coronary artery disease (Burtscher et al., 2004). Recent studies (Haufe et al., 2008; Wiesner et al., 2010) have also reported that sustained hypoxia may be of benefit to weight management programs of obese patients (Urdampilleta et al., 2012; Kayser and Verges, 2013). Both exercise (Williams et al., 2002) and/or intermittent hypoxia (Burtscher et al., 2004; Shatilo et al., 2008) have been suggested to positively influence age-related alterations in elderly individuals. Finally, living at altitude seems to have contradictory effects on different mortality risk factors. Therefore, this essay summarizes recent evidences suggesting that exercising in hypoxia might be a valuable and viable “therapeutic strategy.” We discuss the benefits and risks/limitations in (i) hypertensive (ii) obese, (iii) elderly individuals. Since the benefits of being active have been extensively investigated in these three groups of individuals (see respective reviews on the effects of physical activity in Cherubini et al., 1998; Baillot et al., 2014; Borjesson et al., 2016), the present article focus on the potential additional health benefits provided by hypoxic exercise, when compared to normoxic exercise. For safety and practical reasons, patients cannot access high altitude (even by using hypoxic devices) and preferably stay at moderate altitude (1800–3000 m). In this setting, exercise is used to increase the overall hypoxia-induced metabolic stress and thereby provide benefits beyond those achievable by normoxic therapeutic training modalities.

Relationships between anthropometric measures and athletic performance, with special reference to repeated-sprint ability, in the Qatar national soccer team

Abstract The aim of this study was to determine potential relationships between anthropometric parameters and athletic performance with special consideration to repeated-sprint ability (RSA). Sixteen players of the senior male Qatar national soccer team performed a series of anthropometric and physical tests including countermovement jumps without (CMJ) and with free arms (CMJwA), straight-line 20 m sprint, RSA (6 × 35 m with 10 s recovery) and incremental field test. Significant (P < 0.05) relationships occurred between muscle-to-bone ratio and both CMJs height (r ranging from 0.56 to 0.69) as well as with all RSA-related variables (r < –0.53 for sprinting times and r = 0.54 for maximal sprinting speed) with the exception of the sprint decrement score (Sdec). The sum of six skinfolds and adipose mass index were largely correlated with Sdec (r = 0.68, P < 0.01 and r = 0.55, P < 0.05, respectively) but not with total time (TT, r = 0.44 and 0.33, P > 0.05, respectively) or any standard athletic tests. Multiple regression analyses indicated that muscular cross-sectional area for mid-thigh, adipose index, straight-line 20 m time, maximal sprinting speed and CMJwA are the strongest predictors of Sdec (r2 = 0.89) and TT (r2 = 0.95) during our RSA test. In the Qatar national soccer team, players’ power-related qualities and RSA are associated with a high muscular profile and a low adiposity. This supports the relevance of explosive power for the soccer players and the larger importance of neuromuscular qualities determining the RSA.

Sprint performance under heat stress: A review.

Training and competition in major track‐and‐field events, and for many team or racquet sports, often require the completion of maximal sprints in hot (>30 °C) ambient conditions. Enhanced short‐term (<30 s) power output or single‐sprint performance, resulting from transient heat exposure (muscle temperature rise), can be attributed to improved muscle contractility. Under heat stress, elevations in skin/core temperatures are associated with increased cardiovascular and metabolic loads in addition to decreasing voluntary muscle activation; there is also compelling evidence to suggest that large performance decrements occur when repeated‐sprint exercise (consisting of brief recovery periods between sprints, usually <60 s) is performed in hot compared with cool conditions. Conversely, poorer intermittent‐sprint performance (recovery periods long enough to allow near complete recovery, usually 60–300 s) in hotter conditions is solely observed when exercise induces marked hyperthermia (core temperature >39 °C). Here we also discuss strategies (heat acclimatization, precooling, hydration strategies) employed by “sprint” athletes to mitigate the negative influence of higher environmental temperatures.

On the use of mobile inflatable hypoxic marquees for sport-specific altitude training in team sports

Background/aim With the evolving boundaries of sports science and greater understanding of the driving factors in the human performance physiology, one of the limiting factors has now become the technology. The growing scientific interest on the practical application of hypoxic training for intermittent activities such as team and racket sports legitimises the development of innovative technologies serving athletes in a sport-specific setting. Methods Description of a new mobile inflatable simulated hypoxic equipment. Results The system comprises two inflatable units—that is, a tunnel and a rectangular design, each with a 215 m3 volume and a hypoxic trailer generating over 3000 Lpm of hypoxic air with FiO2 between 0.21 and 0.10 (a simulated altitude up to 5100 m). The inflatable units offer a 45 m running lane (width=1.8 m and height=2.5 m) as well as a 8 m×10 m dome tent. FiO2 is stable within a range of 0.1% in normal conditions inside the tunnel. The air supplied is very dry—typically 10–15% relative humidity. Conclusions This mobile inflatable simulated hypoxic equipment is a promising technological advance within sport sciences. It offers an opportunity for team-sport players to train under hypoxic conditions, both for repeating sprints (tunnel configuration) or small-side games (rectangular configuration).

Intrasession and Intersession Reliability of Running Mechanics During Treadmill Sprints

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.

Repeated maximal-intensity hypoxic exercise superimposed to hypoxic residence boosts skeletal muscle transcriptional responses in elite team-sport athletes

To determine whether repeated maximal‐intensity hypoxic exercise induces larger beneficial adaptations on the hypoxia‐inducible factor‐1α pathway and its target genes than similar normoxic exercise, when combined with chronic hypoxic exposure.

Comparison of Four Sections for Analyzing Running Mechanics Alterations During Repeated Treadmill Sprints.

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.