Repeated practice runs during on-snow training do not generate any measurable neuromuscular alterations in elite alpine skiers

Background Alpine skiers typically train using repeated practice runs requiring high bursts of muscle activity but there is little field-based evidence characterizing neuromuscular function across successive runs. Purpose To examine the impact of repeated ski runs on electromyographic activity (EMG) of the knee extensors and flexors in elite alpine skiers. Methods Nineteen national team alpine skiers were tested during regular ski training [Slalom (SL), Giant Slalom (GS), Super Giant Slalom and Downhill (Speed)] for a total of 39 training sessions. The surface EMG of the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF) and semimembranosus/semitendinosus (SMST) muscles was continuously recorded along with right knee and hip angles. The EMG root mean square signal was normalized to a maximal voluntary contraction (%MVC). The first and fourth runs of the training session were compared. Results There was no meaningful main effect of run on EMG relative activation time or mean power frequency beyond the skier's intrinsic variability. However, EMG activity of the vastii increased from the first to the fourth run in SL [VM, ~+3%MVC for IL and outside leg (OL), p = 0.035)], speed (VL, IL:+6%/OL:+11%, p = 0.015), and GS (VM, IL:0/OL:+7%, p < 0.001); the later with an interaction with leg (p < 0.001) due to a localized increase on the OL. The run time and turn time did not change from the first to the fourth run. There were no meaningful changes in angular velocities, amplitude of movement, or maximal and minimal angles. Conclusion Neuromuscular activity remains highly stable in elite skiers with low variability across four runs

Association between thermal responses, medical events, performance, heat acclimation and health status in male and female elite athletes during the 2019 Doha World Athletics Championships

Please read abstract in the article.The World Athletics Health and Science Department.http://bjsm.bmj.comhj2022Sports Medicin

Contribution à l'analyse de l'activité neuromusculaire des skieurs alpins d'élite lors de tests isocinétiques et en conditions réelles d'entraînement

The overall aim of this PhD was to characterize the neuromuscular function of elite alpine skiers in regard to their specialty to enhance isokinetic screening protocols. The first part of this work is a review of the literature. The second part describes the general methods used for the experimental protocols. The third part presents the results and publications in five chapters. In the first chapter, a fatiguing task at 180°.s-1 showed that peak torque was less sensitive than rapid torque development to fatigue and/or environmental conditions. In the chapter II, a new method called Statistical Parametric Mapping (SPM) was used to describe thigh muscle torque of the skiers with respect to sex and discipline factors. The SPM analysis allowed detecting sub-group differences that could not be detected via a traditional scalar analysis of the peak torques. For example, females displayed hamstrings-to-quadriceps ratio deficits toward knee extension only. Chapters III to V report on-snow data to characterize the specificities of the alpine skiing disciplines. Chapters III-IV showed a scalar analysis of the ski cycle to allow comparison with the literature and update it following the major changes of the last twenty years. In particular, the individualization of an isometric phase led us to better characterize the speed disciplines. In Chapter V, the SPM method used in chapter I was used to analyze the discipline effect on the ski cycle structure. Activation pattern and EMG level varied according to the disciplines and muscles studiedL’objectif général de ce travail était de caractériser la fonction neuromusculaire des skieurs alpins élites, notamment au regard de leur discipline de spécialité, afin d’améliorer les procédures de tests isocinétiques réalisés en routine. La première partie du travail est une revue de littérature. La seconde partie décrit la méthodologie générale. La troisième partie présente les résultats et publications en cinq chapitres. Dans le chapitre I, un protocole de fatigue isocinétique à 180°.s-1 a montré le manque de sensibilité du pic de couple comparé au taux de développement de force pour détecter les baisses de forces induites par la fatigue et/ou les conditions environnementales. Au chapitre II, une nouvelle méthode d’analyse des tests isocinétiques par cartographie statistique paramétrique (SPM) a été utilisée pour analyser la force des muscles extenseurs et fléchisseurs de la cuisse chez des skieurs en fonction du sexe et de la discipline. L’analyse traditionnelle des tests isocinétiques via les pics de couples s’est révélée moins performante que l’analyse SPM pour détecter des différences entre les sous-groupes. Les femmes présentent des déficits du ratio ischiojambiers / quadriceps à proximité de l’extension du genou uniquement. Les chapitres III à V rapportent des résultats de terrain pour mettre en avant les besoins spécifiques du ski de haut niveau. Les chapitres III-IV présentent une analyse par scalaires des phases du cycle de virages en ski afin d’avoir des points de comparaison avec la littérature, ainsi qu’une mise à jour de celle-ci prenant en compte les changements en ski alpin de ces dernières années. En particulier l’isolement d’une phase isométrique a permis de mieux caractériser les disciplines de vitesse. Au chapitre V, la méthode SPM a été utilisée pour analyser les effets de la discipline alpine sur la structure du cycle de ski. La séquence des activations ainsi que leur niveau variaient selon la discipline et le muscle étudié

Contribution to the neuromuscular analysis of elite alpine skiers during isokinetic assessment and on-hill racing

L’objectif général de ce travail était de caractériser la fonction neuromusculaire des skieurs alpins élites, notamment au regard de leur discipline de spécialité, afin d’améliorer les procédures de tests isocinétiques réalisés en routine. La première partie du travail est une revue de littérature. La seconde partie décrit la méthodologie générale. La troisième partie présente les résultats et publications en cinq chapitres. Dans le chapitre I, un protocole de fatigue isocinétique à 180°.s-1 a montré le manque de sensibilité du pic de couple comparé au taux de développement de force pour détecter les baisses de forces induites par la fatigue et/ou les conditions environnementales. Au chapitre II, une nouvelle méthode d’analyse des tests isocinétiques par cartographie statistique paramétrique (SPM) a été utilisée pour analyser la force des muscles extenseurs et fléchisseurs de la cuisse chez des skieurs en fonction du sexe et de la discipline. L’analyse traditionnelle des tests isocinétiques via les pics de couples s’est révélée moins performante que l’analyse SPM pour détecter des différences entre les sous-groupes. Les femmes présentent des déficits du ratio ischiojambiers / quadriceps à proximité de l’extension du genou uniquement. Les chapitres III à V rapportent des résultats de terrain pour mettre en avant les besoins spécifiques du ski de haut niveau. Les chapitres III-IV présentent une analyse par scalaires des phases du cycle de virages en ski afin d’avoir des points de comparaison avec la littérature, ainsi qu’une mise à jour de celle-ci prenant en compte les changements en ski alpin de ces dernières années. En particulier l’isolement d’une phase isométrique a permis de mieux caractériser les disciplines de vitesse. Au chapitre V, la méthode SPM a été utilisée pour analyser les effets de la discipline alpine sur la structure du cycle de ski. La séquence des activations ainsi que leur niveau variaient selon la discipline et le muscle étudiésThe overall aim of this PhD was to characterize the neuromuscular function of elite alpine skiers in regard to their specialty to enhance isokinetic screening protocols. The first part of this work is a review of the literature. The second part describes the general methods used for the experimental protocols. The third part presents the results and publications in five chapters. In the first chapter, a fatiguing task at 180°.s-1 showed that peak torque was less sensitive than rapid torque development to fatigue and/or environmental conditions. In the chapter II, a new method called Statistical Parametric Mapping (SPM) was used to describe thigh muscle torque of the skiers with respect to sex and discipline factors. The SPM analysis allowed detecting sub-group differences that could not be detected via a traditional scalar analysis of the peak torques. For example, females displayed hamstrings-to-quadriceps ratio deficits toward knee extension only. Chapters III to V report on-snow data to characterize the specificities of the alpine skiing disciplines. Chapters III-IV showed a scalar analysis of the ski cycle to allow comparison with the literature and update it following the major changes of the last twenty years. In particular, the individualization of an isometric phase led us to better characterize the speed disciplines. In Chapter V, the SPM method used in chapter I was used to analyze the discipline effect on the ski cycle structure. Activation pattern and EMG level varied according to the disciplines and muscles studie

Intérêt de l immobilisation des fractures du poignet par attelle thermoformable en urgence (résultats de l étude pilote sur l hiver 2008-2009 en montagne)

Une étude de cohorte descriptive a été réalisée pour évaluer la tolérance, l efficacité et l innocuité des attelles thermoformées dans l immobilisation des fractures du poignet. Cette immobilisation produit de bons résultats fonctionnels, radiologiques, et est bien tolérée dans le traitement des fractures du poignet en urgence. Un essai libre prospectif a été conduit dans 2 cabinets médicaux de station durant l hiver 2008-2009.136 patients âgés de 5 à 80 ans ont été inclus, avec un diagnostic de fracture du poignet dans le cabinet de montagne. Nous avons utilisé un questionnaire pour évaluer la douleur, la satisfaction et l état d activité du patient. L immobilisation avec attelle thermoformée était associée avec les résultats suivants : une durée de douleur de 10,4 jours avec une médiane de 4 jours ; temps de reprise des activités normales à 12,5 jours avec une médiane de 7 jours. La sévérité de la douleur initiale était de 57,5/100 sur l EVA, diminuée à 31,1/100 après immobilisation. Les patients qui ont eu cette attelle présentaient un taux de déplacement secondaire de 2,2%. Le taux de satisfaction atteignait presque 90% (88,7%) ; 89,6% trouvaient l attelle confortable. Dans les complications, il a été noté 6,5% de mauvaise tolérance cutanée. Les médecins assurant le suivi ont estimé l attelle adaptée dans 87,5% des cas. 93,8% de bons résultats fonctionnels ont été obtenus. L attelle thermoformée a été bien tolérée dans cette étude préliminaire. Les attelles thermoformées pourraient remplacer avantageusement le plâtre dans un grand nombre de cas. Cependant ceci reste à évaluer lors d une étude ultérieure comparative.GRENOBLE1-BU Médecine pharm. (385162101) / SudocSudocFranceF

Epidemiology and risk factors for heat illness: 11 years of Heat Stress Monitoring Programme data from the FIVB Beach Volleyball World Tour

Objectives: To analyse 11 years of FIVB heat stress-monitoring data to determine the relative influence of the different environmental parameters in increasing the likelihood of a heat-related medical time-out (MTOheat). Methods: A total of 8530 matches were recorded. The referee measured air temperature, black globe temperature, relative humidity and wet-bulb globe temperature (WBGT) before the matches, and registered the MTOheat. The absolute humidity was computed at posteriori. Results: There were 20 MTOheat cases, but only 3 resulted in forfeiting the match. MTOheat incidence was not statistically impacted by sex (p=0.59). MTOheat cases were more prevalent during the games played in Asia during the 4th quarter of the year (p<0.001). Two cases of MTOheat experienced diarrhoea or gastroenteritis during the 5 preceding days; both of them forfeited the match. A principal component analysis showed a specific environmental profile for the matches with MTOheat. They occurred at higher WBGT, temperatures and absolute humidity (p<0.001), but with a lower relative humidity (p=0.027). Conclusions: The current data showed that an increase in ambient or black globe temperature, but not relative humidity, increased the risk of a MTOheat; but that the absolute risk remained low in elite beach volleyball players. However, suffering or recovering from a recent illness may represent a risk factor for a MTOheat to lead to player forfeit

On-Field Ski Kinematic According to Leg and Discipline in Elite Alpine Skiers

International audienceThis study used wireless technology to investigate joint kinematic characteristics of the four alpine skiing disciplines. Knee and hip angles were measured in 20 national team alpine skiers during 253 ski runs under FIS regulation, including: 85 Slalom (SL), 123 Giant Slalom (GS), 29 Super Giant Slalom (SG), and 16 Downhill (DH). Data were analyzed by outside (OL, n = 2,087) and inside leg (IL, n = 2,015). The proportion of concentric and eccentric phases (extension and flexion respectively for the knee extensors) as well as the proportion of the quasi-isometric phase defined between ±20 • .s −1 depended on the discipline in interaction with the IL/OL (p 1.8), suggesting a highly dynamic style. Quasi-isometric mode was significantly longer on OL than IL in GS (34 vs. 20%, p < 0.001, d = 1.16) and SG (42 vs. 28%, p < 0.001, d = 1.11) but was significantly longer on IL than OL in SL (19 vs. 11%, p < 0.001, d = 0.64). Thus, GS and SG showed similarities, with a significantly faster knee eccentric mean angular velocity on IL compared to OL (GS −58 vs. −54 • .s −1 , SG −52 vs. −45 • .s −1 , p < 0.001, d ≥ 0.22) whereas SL showed an opposite pattern (−72 vs. −89 • .s −1 , p < 0.001, d = 1.10). The quasi-isometric phase was overlooked in previous studies but is crucial to consider. The current data may be used to train the outside and inside leg specificities incorporating discipline-specific contraction modes and exercises

Thermoregulation and shivering responses in elite alpine skiers

International audienceThis study aimed to characterize the thermoregulatory responses of elite alpine skiers. Core(gastro-intestinal) and skin temperatures were recorded continuously from 4 national teamskiers representing 18 training-sessions for a total of 83 ski runs (average ambient temperature1.9ºC). Shivering responses were estimated from quadriceps and hamstrings EMG recordingsduring 77 chairlifts. Temperature responses were also obtained from 6 accompanying staffsrepresenting 16 training-sessions (passive in 10 cases, following the skiers in 6 cases). Coretemperature of the skiers (p<0.001) but not the staff (p=0.103) increased during training andwas higher in skiers than staff after one-third of the training session (p<0.006). Conversely,average skin temperature of the skiers decreased during training (p<0.001) and was lower inskiers than staff for the second half of the training. Muscle activity during chairlifts remainedbelow 1% and there was no meaningful shivering. Muscle activity decreased whilst mean andmedian power frequency increased during the chairlift (p<0.020). Muscle activity was alsolower during the last lift than the first one whilst mean and median power frequency werehigher (p<0.020). In conclusion, skin temperature decreased during Slalom and Giant Slalomin elite alpine skiers, likely due to the limited insulative capacity of the racing suit and the highvelocity increasing convective heat loss. Conversely, core temperature increased during thetraining session suggesting that the metabolic heat production was larger than the convectiveheat loss, and was also sufficient to maintain homeostasis without shivering

Angle specific analysis of hamstrings and quadriceps isokinetic torque identify residual deficits in soccer players following ACL reconstruction: a longitudinal investigation

Analysing the isokinetic curve is important following ACL reconstruction as there may be deficits in torque production at specific points throughout the range of motion. We examined isokinetic (60°.s-1) torque-angle characteristics in 27 male soccer players (24.5 ± 3.9 years) at 3 time-points (17 ± 5; 25 ± 6; and 34 ± 7 weeks post-surgery). Extracted data included knee flexor and extensor peak torque, conventional hamstrings: quadriceps (H/Q) ratio, and angle-specific torque using Statistical Parametric Mapping (SPM). There were significant involved limb increases in extension peak torque at each assessment (p<0.001); however, asymmetry favouring the un-involved limb was observed (p<0.01). Flexion peak torque was greater on the un-involved limb at assessments 1 and 2 only (p<0.05). The angle of peak torque was not significantly different at individual time-points or within-limbs across the 3 assessments. SPM revealed involved limb angle-specific reductions in extension torque across the full range of motion at time-points 1 and 2 (p<0.001) but only in angles [51-80°] at assessment 3 (p<0.05). Between limb H/Q angle differences [33-45°] were shown at assessments 2 and 3. The ratio ranged from 1.60-0.74 depending on the angle tested. Angle-specific moment curves are useful for monitoring patterns of strength development during rehabilitation

Muscle-tendon unit length changes in knee extensors and flexors during alpine skiing

International audienceThis study characterised the thigh muscle-tendon unit length variations (MTUv) in elite alpine skiing. MTUv were modelled for seven muscles from knee and hip angles in 17 national team skiers during 1602 cycles (546 Slalom (SL), 908 Giant-Slalom (GS), 136 Super-Giant (SG) and 12 Downhill (DH) cycles). The biarticular rectus femorisshowed a dynamic pattern on both legs, especially in SL. On the other side, vastii displayed a stable length on the inside leg in all disciplines (37–46% of the cycle), contrasting with their dynamic behaviour on the outside leg being quasi-static for only 3% (SL) to 27% (DH) of the cycle. SL showed the largest amplitude of MTUv followed by GS, SG and DH. For vastus lateralis, MTUv was ~60%Lr. s −1 in SL but only ~12%Lr.s−1 in DH. In SL, a fine desynchronisation between both joints led to nearly constant MTUv (slow lengthening lasting ~45-51% of the cycle) for the biarticular hamstrings separated by faster variations during turn switch from outside to insideleg. In summary, biarticular MTUv were not characterised by singlejoint behaviours, suggesting that extrapolating contraction regimen from knee joint only is not accurate in alpine skiing