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

Effects of Action Observation and Action Observation Combined with Motor Imagery on Maximal Isometric Strength

Action observation (AO) alone or combined with motor imagery (AO + MI) has been shown to engage the motor system. While recent findings support the potential relevance of both techniques to enhance muscle function, this issue has received limited scientific scrutiny. In the present study, we implemented a counterbalanced conditions design where 21 participants performed 10 maximal isometric contractions (12-s duration) of elbow flexor muscles against a force platform. During the inter-trial rest periods, participants completed i) AO of the same task performed by an expert athlete, ii) AO + MI, i.e. observation of an expert athlete while concurrently imagining oneself performing the same task, and iii) watching passively a video documentary about basketball shooting (Control). During force trials, we recorded the total force and integrated electromyograms from the biceps brachii and anterior deltoideus. We also measured skin conductance from two finger electrodes as an index of sympathetic nervous system activity. Both AO and AO + MI outperformed the Control condition in terms of total force (2.79–3.68%, p < 0.001). For all conditions, we recorded a positive relationship between the biceps brachii activation and the total force developed during the task. However, only during AO was a positive relationship observed between the activation of the anterior deltoideus and the total force. We interpreted the results with reference to the statements of the psycho-neuromuscular theory of mental practice. Present findings extend current knowledge regarding the priming effects of AO and AO + MI on muscle function, and may contribute to the optimization of training programs in sports and rehabilitation

A New Algorithm to Reduce and Individualize HRV Recording Time

International audienc

The impact of breathing on HRV measurements: Implications for the longitudinal follow-up of athletes

International audienc

The breathing effect of the LF/HF ratio in the heart rate variability measurements of athletes

International audienc

Predicting recovery oxygen consumption after cycle exercise

Le but de l’étude était de construire un modèle mathématique à partir des données de la littérature permettant de prédire l’amplitude de l’«excess post-exercise oxygen consumption» (EPOC) et d’analyser l’impact du déficit en O2 (DO2) (L), de la quantité d’O2 consommée (EOC) (L), de l’intensité de l’exercice (P) (% VO2max et de la durée (t) (min). Quinze études de la littérature donnant 33 valeurs d’EPOC (n = 33) mesurées après des exercices sur ergocycle de puissance sous-maximale variant de 29 % à 80 % VO2max sont sélectionnées