French National Institute of Sport


French National Institute of Sport


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Schaal K.,French National Institute of Sport | Schaal K.,University of California at Davis | Le Meur Y.,French National Institute of Sport | Louis J.,French National Institute of Sport | And 4 more authors.
Medicine and Science in Sports and Exercise | Year: 2015

Introduction Elite athletes frequently undergo periods of intensified training (IT) within their normal training program. These periods can lead athletes into functional overreaching, characterized by high perceived fatigue, impaired sleep, and performance. Because whole-body cryostimulation (WBC) has been proven to be an effective recovery method in the short term (<76 h), we investigated whether daily WBC sessions during IT could prevent exercise and sleep-related signs of overreaching. Methods After a normal training week (BASE), 10 elite synchronized swimmers performed two 2-wk IT periods in a randomized crossover fashion using WBC daily (ITWBC) or not (ITCON), separated by 9 d of light training. Swim time trials (400 m) were performed at BASE and after each IT to quantify blood lactate ([La-]B), HR (HR400), salivary alpha amylase ([α-amylase]s400), and cortisol ([cortisol]s400) responses. Swimmers wore a wrist actigraph nightly to monitor sleep patterns. Results Swim speed (400 m), [La-]B400, and [α-amylase]s400 decreased from BASE to ITCON, although no significant changes were found after ITWBC. Decreased swim speed was correlated to decreased HR400 and [cortisol]s400. During ITCON, significant decreases in actual sleep duration (-21 ± 7 min) and sleep efficiency (-1.9% ± 0.8%) were observed, with increased sleep latency (+11 ± 5 min) and fatigue compared with BASE, although these variables did not change during ITWBC. Using a qualitative statistical analysis, we observed that daily WBC use resulted in a 98%, 59%, 66%, and 78% chance of preserving these respective variables compared with ITCON. Conclusion WBC use during IT helped mitigate the signs of functional overreaching observed during ITCON, such as reduced sleep quantity, increased fatigue, and impaired exercise capacity. These results support the daily use of WBC by athletes seeking to avoid functional overreaching during key periods of competition preparation. © 2014 by the American College of Sports Medicine.

PubMed | Australian Catholic University, University Cote dAzur and French National Institute of Sport
Type: Journal Article | Journal: Nutrients | Year: 2016

Sleep-low consists of a sequential periodization of carbohydrate (CHO) availability-low glycogen recovery after train high glycogen-depleting interval training, followed by an overnight-fast and light intensity training (train low) the following day. This strategy leads to an upregulation of several exercise-responsive signaling proteins, but the chronic effect on performance has received less attention. We investigated the effects of short-term exposure to this strategy on endurance performance.Following training familiarization, 11 trained cyclists were divided into two groups for a one-week intervention-one group implemented three cycles of periodized CHO intake to achieve the sleep-low strategy over six training sessions (SL, CHO intake: 6 gkgSL improved their performance (mean: +3.2%; Implementing the sleep-low strategy for one week improved performance by the same magnitude previously seen in a three-week intervention, without any significant changes in selected markers of metabolism.

PubMed | University of Nice Sophia Antipolis, University of California at Davis and French National Institute of Sport
Type: Journal Article | Journal: PloS one | Year: 2015

Recent research on whole-body cryotherapy has hypothesized a major responsibility of head cooling in the physiological changes classically reported after a cryostimulation session. The aim of this experiment was to verify this hypothesis by studying the influence of exposing the head to cold during whole-body cryostimulation sessions, on the thermal response and the autonomic nervous system (ANS). Over five consecutive days, two groups of 10 participants performed one whole-body cryostimulation session daily, in one of two different systems; one exposing the whole-body to cold (whole-body cryostimulation, WBC), and the other exposing the whole-body except the head (partial-body cryostimulation, PBC).10 participants constituted a control group (CON) not receiving any cryostimulation. In order to isolate the head-cooling effect on recorded variables, it was ensured that the WBC and PBC systems induced the same decrease in skin temperature for all body regions (mean decrease over the 5 exposures: -8.6C 1.3C and -8.3 0.7C for WBC and PBC, respectively), which persisted up to 20-min after the sessions (P20). The WBC sessions caused an almost certain decrease in tympanic temperature from Pre to P20 (-0.28 0.11C), while it only decreased at P20 (-0.14 0.05C) after PBC sessions. Heart rate almost certainly decreased after PBC (-8.6%) and WBC (-12.3%) sessions. Resting vagal-related heart rate variability indices (the root-mean square difference of successive normal R-R intervals, RMSSD, and high frequency band, HF) were very likely to almost certainly increased after PBC (RMSSD:+49.1%, HF: +123.3%) and WBC (RMSSD: +38.8%, HF:+70.3%). Plasma norepinephrine concentration was likely increased in similar proportions after PBC and WBC, but only after the first session. Both cryostimulation techniques stimulated the ANS with a predominance of parasympathetic tone activation from the first to the fifth session and in slightly greater proportion with WBC than PBC. The main result of this study indicates that the head exposure to cold during whole-body cryostimulation may not be the main factor responsible for the effects of cryostimulation on the ANS.

Doron J.,French National Institute of Sport | Martinent G.,University Claude Bernard Lyon 1
Journal of Sports Sciences | Year: 2016

This study examined the trajectories and within-person synergies of psychological processes during the final stages of matches. A process-oriented approach was used with nine women elite fencers during an international competition. Multiple assessments of perceived control, threat and challenge appraisals, problem- and emotion-focused coping, positive and negative affects were completed after each touches using video recall method. Multilevel growth curve analyses (MGCAs) indicated that winning and losing matches were each characterised by distinct psychological processes. Specifically, perceived control, challenge appraisal, problem- and emotion-focused coping, and positive affects increased linearly and threat appraisal decreased linearly for wining matches, whereas negative affects increased linearly for losing matches. Regarding the within-person synergies of psychological processes, MGCAs indicated that (1) perceived control and challenge appraisal were significantly associated with problem- and emotion-focused coping for losing matches, the strength of these associations remaining consistent across touches; (2) problem-focused coping was significantly associated with negative affects whereas emotion-focused coping was significantly associated with positive affects for winning matches, the strength of these associations remaining consistent across touches; and (3) problem- and emotion-focused coping were significantly associated with negative affects for losing matches, the linear trajectory of negative affects accelerating at times when athletes had higher levels of emotion-focused coping. Overall, this study provided insights into transactional processes during competition. © 2015 Taylor & Francis.

PubMed | University of Technology, Sydney and French National Institute of Sport
Type: | Journal: Sports medicine (Auckland, N.Z.) | Year: 2016

Despite the predominance of research on physical performance in the heat, many activities require high cognitive functioning for optimal performance (i.e. decision making) and/or health purposes (i.e. injury risk). Prolonged periods of demanding cognitive activity or exercise-induced fatigue will incur altered cognitive functioning. The addition of hot environmental conditions will exacerbate poor cognitive functioning and negatively affect performance outcomes. The present paper attempts to extract consistent themes from the heat-cognition literature to explore cognitive performance as a function of the level of heat stress encountered. More specifically, experimental studies investigating cognitive performance in conditions of hyperthermia, often via the completion of computerised tasks (i.e. cognitive tests), are used to better understand the relationship between endogenous thermal load and cognitive performance. The existence of an inverted U-shaped relationship between hyperthermia development and cognitive performance is suggested, and highlights core temperatures of ~38.5C as the potential threshold for hyperthermia-induced negative cognitive performance. From this perspective, interventions to slow or blunt thermal loads and protect both task- and hyperthermia-related changes in task performances (e.g. cooling strategies) could be used to great benefit and potentially preserve cognitive performance during heat strain.

PubMed | University Hospital Lariboisiere, University of Technology, Sydney and French National Institute of Sport
Type: Journal Article | Journal: Scandinavian journal of medicine & science in sports | Year: 2015

To determine if pre-cooling (PC) following heat-acclimatization (HA) can further improve self-paced endurance performance in the heat, 13 male triathletes performed two 20-km cycling time-trials (TT) at 35C, 50% relative humidity, before and after an 8-day training camp, each time with (PC) or without (control) ice vest PC. Pacing strategies, physiological and perceptual responses were assessed during each TT. PC and HA induced moderate (+1018W; effect size [ES] 4.4 4.6%) and very large (+2819W; ES 11.74.1%) increases in power output (PO), respectively. The overall PC effect became unclear after HA (+414W; ES 1.43.0%). However, pacing analysis revealed that PC remained transiently beneficial post-HA, i.e., during the first half of the TT. Both HA and PC pre-HA were characterized by an enhanced PO without increased cardio-thermoregulatory or perceptual disturbances, while post-HA PC only improved thermal comfort. PC improved 20-km TT performance in unacclimatized athletes, but an 8-day HA period attenuated the magnitude of this effect. The respective converging physiological responses to HA and PC may explain the blunting of PC effectiveness. However, perceptual benefits from PC can still account for the small alterations to pacing noted post-HA.

PubMed | University of Nantes and French National Institute of Sport
Type: Journal Article | Journal: Muscle & nerve | Year: 2016

In this study we aimed to quantify the effect of exercise-induced muscle damage on both the electrochemical and mechanical components of electromechanical delay using very-high-frame-rate ultrasound.Fifteen participants underwent electrically evoked contractions of the medial gastrocnemius muscle with an ultrasound transducer on the muscle belly and on the myotendinous junction, before, 1 hour, and 48 hours after eccentric exercise of the plantar flexor muscles.Maximal isometric plantar flexor torque was significantly lower at 1 hour (-41.114.9%; P=0.0001) and 48 hours (-11.914.9%; P=0.038) post-exercise compared with pre-exercise. However, the delay between electrical stimulation and the onset of muscle activation, the delay between electrical stimulation and myotendinous junction motion, and the electromechanical delay were not altered significantly by eccentric exercise (P=0.063).These findings suggest that moderate muscle damage does not affect the time for the electrochemical or mechanical components of electromechanical delay. Muscle Nerve 54: 136-141, 2016.

PubMed | University of Nantes and French National Institute of Sport
Type: | Journal: Scandinavian journal of medicine & science in sports | Year: 2016

Little is known about how team sport athletes individually and collectively experience sources of stress during competitive sport encounters. This study aimed to examine the nature of the stressors team sport athletes appraised during games at individual and team levels, as well as their degree of synchronization during an unfolding game. Through individual self-confrontation interviews, the activities of nine basketball players of the same team were examined in detail. The results revealed that 12 categories of stressors were reported, and categorized into two larger units reflecting stressors perceived as affecting (a) the team functioning as a whole and (b) a players own functioning. Thus, the nature and degree of similarity of the game-specific stressors experienced by basketball players within a single team were identified during a game. In addition, the findings showed six different patterns of synchronizations of team members stressors, as well as their changes over the course of the game. They provided support for the synchronized appraisal and experience of stressors within a team during a game. By adopting an interpersonal perspective and examining the temporal interplay in team members activities, this study shed light on stress within teams.

Marquet L.-A.,University of Nice Sophia Antipolis | Hausswirth C.,French National Institute of Sport | Hays A.,CREPS Sud Est | Vettoretti F.,CREPS Sud Est | Brisswalter J.,University of Nice Sophia Antipolis
International Journal of Sports Physiology and Performance | Year: 2015

Purpose: To assess the impact of between-training-sessions recovery strategies (passive [PAS], active [ACT], cold-water immersion [CWI], and ingestion of a recovery drink [NUTR]) on maximal cycling performance, perceptions of delayed-onset muscle soreness (DOMS), and fatigue in world-class BMX riders. Methods: Eleven elite BMX athletes, members of the French national team (top country in the 2011 international ranking, 4 medals at the 2012 World Championships, top European country), participated in the study, which involved standardized training periods. Athletes performed 3 maximal-sprint power tests: the first day of the week before the training session and before and after training on the third day of the week (D3). The recovery strategy was randomly assigned to each participant on day 2 immediately after the last training period of the day. Perceptions of DOMS and general fatigue were recorded on D3. Results: After training on D3, the decrease in maximal-sprint power (Pmax) was significantly greater for PAS than with CWI (P = .02) and NUTR (P = .018). Similar results were found with ACT (vs CWI P = .044, and vs NUTR P = .042). Self-reported DOMS and fatigue were significantly greater after PAS than after other strategies. Conclusions: For elite BMX riders, between training days, nutritional and/or CWI recovery strategies appear to be best for reducing muscle fatigue and increasing the capacity to withstand the training schedule. © 2015 Human Kinetics, Inc.

PubMed | University of Nice Sophia Antipolis, Liverpool John Moores University and French National Institute of Sport
Type: Journal Article | Journal: European journal of applied physiology | Year: 2016

We investigated the effects of a 3-week dietary periodization on immunity and sleep in triathletes.21 triathletes were divided into two groups with different nutritional guidelines during a 3-week endurance training program including nine twice a day sessions with lowered (SL group) or maintained (CON group) glycogen availability during the overnight recovery period. In addition to performance tests, sleep was monitored every night. Systemic and mucosal immune parameters as well as the incidence of URTI were monitored every week of the training/nutrition protocol. Two-ways ANOVA and effect sizes were used to examine differences in dependent variables between groups at each time point.The SL group significantly improved 10km running performance (-1min 13s, P<0.01, d=0.38), whereas no improvement was recorded in the CON group (-2s, NS). No significant changes in white blood cells counts, plasma cortisol and IL-6 were recorded over the protocol in both groups. The vitamin D status decreased in similar proportions between groups, whereas salivary IgA decreased in the SL group only (P<0.05, d=0.23). The incidence of URTI was not altered in both groups. All participants in both groups went to bed earlier during the training program (SL -20min, CON -27min, P<0.05, d=0.28). In the SL group, only sleep efficiency slightly decreased by 1.1% (P<0.05, d=0.25) and the fragmentation index tended to increase at the end of the protocol (P=0.06).Sleeping and training the next morning regularly with reduced glycogen availability has minimal effects on selected markers of immunity, the incidence of URTI and sleeping patterns in trained athletes.

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