Caractérisation des propriétés mécaniques et géométriques des structures tendineuses et musculaires des fléchisseurs plantaires de la cheville in vivo. Effets de l’entraînement pliométrique et excentrique

Plyometric and eccentric contractions lead to a different use of potential elastic energy by muscular and tendinous structures. To determine the geometrical and mechanical properties adaptations of the ankle plantar flexors musculo-tendinous complex to 14 weeks of plyometric and eccentric training, a methodological development was required. The geometry of the triceps surae muscles and the Achilles tendon and also the mechanical properties of each elastic components based on Zajac’s rheological modeling (1989) were assessed non-invasively in vivo. The results showed that the tendon and muscles mechanical properties changed in a specific and different way according to the training modality in order to optimize the muscular tension transmission to the skeleton and potential elastic energy storage-recoil processes during movement. Plyometric and eccentric trainings lead to a decrease of the muscle stiffness allowing an increase of the energy stored. Only plyometric training induced an increase in tendon stiffness and a decrease in energy dissipated by the tendon allowing a better restitution of the elastic energy stored. The eccentric training did not change the tendon mechanical properties, the aim of eccentric contraction consisting in dissipating the stored energy rather than restoring it. The nature of the mechanical properties adaptations in muscles and tendon is rather due to change in intrinsic mechanical properties of muscle and tendinous tissues rather than in geometric parameters of plantar flexors muscles and tendon.Les modalités d’exercice pliométriques et excentriques induisent une utilisation différente de l’énergie élastique potentielle par les structures musculaires et tendineuses. Afin de déterminer les adaptations des structures du système musculo-tendineux des fléchisseurs plantaires de la cheville à 14 semaines d’entraînement pliométrique et excentrique, un travail de développement et de validation méthodologique a été nécessaire. La géométrie des muscles du triceps sural et du tendon d’Achille ainsi que les propriétés mécaniques de l’ensemble des composantes élastiques du modèle rhéologique de Zajac (1989) ont pu être caractérisées non-invasivement in vivo. Les résultats ont montré que les propriétés mécaniques du tendon et du muscle s’adaptent de manière spécifique et différente selon le type d’entraînement afin d’optimiser les processus de transmission de la tension musculaire au squelette et de stockage-restitution de l’énergie potentielle élastique lors du mouvement. Les entraînements pliométrique et excentrique aboutissent à une diminution de la raideur du muscle permettant une augmentation du stockage d’énergie élastique. En revanche, seul l’entraînement pliométrique a provoqué une augmentation de la raideur tendineuse et une diminution de l’énergie dissipée par le tendon permettant une meilleure restitution de l’énergie élastique stockée. L’entraînement excentrique n’a pas modifié les propriétés mécaniques du tendon, la finalité de la contraction excentrique consistant à dissiper l’énergie stockée plutôt qu’à la restituer. La nature des adaptations des propriétés mécaniques des muscles et du tendon après les deux types d’entraînement est associée à une modification de propriétés mécaniques intrinsèques des tissus musculaires et tendineux plutôt qu’à un changement au niveau des paramètres géométriques des muscles et du tendon

New Imaging Methods for Non-invasive Assessment of Mechanical, Structural, and Biochemical Properties of Human Achilles Tendon: A Mini Review

International audienceThe mechanical properties of tendon play a fundamental role to passively transmit forces from muscle to bone, withstand sudden stretches, and act as a mechanical buffer allowing the muscle to work more efficiently. The use of non-invasive imaging methods for the assessment of human tendon's mechanical, structural, and biochemical properties in vivo is relatively young in sports medicine, clinical practice, and basic science. Non-invasive assessment of the tendon properties may enhance the diagnosis of tendon injury and the characterization of recovery treatments. While ultrasonographic imaging is the most popular tool to assess the tendon's structural and indirectly, mechanical properties, ultrasonographic elastography, and ultra-high field magnetic resonance imaging (UHF MRI) have recently emerged as potentially powerful techniques to explore tendon tissues. This paper highlights some methodological cautions associated with conventional ultrasonography and perspectives for in vivo human Achilles tendon assessment using ultrasonographic elastography and UHF MRI

Skeletal Muscle Damage Produced by Electrically Evoked Muscle Contractions

International audienceUnderstanding the physiological/mechanical mechanisms leading to skeletal muscle damage remains one of the challenges in muscle physiology. This review presents the functional, structural, and cellular consequences of electrically evoked submaximal isometric contractions that can elicit severe and localized skeletal muscle damage. Hypotheses related to underlying physiological and mechanical processes involved in severe and localized muscle damage also are discussed

Effects of vertical and horizontal plyometric training on jump performances and sprint force–velocity profile in young elite soccer players

International audiencePurpose: During a soccer match, horizontal acceleration ability during short sprints is determinant for performance. Development of sprint force and velocity qualites have been reported after plyometric training. However, orientation of plyometric training exercises can influence the functional performance. The purpose of this study was to compare the horizontal and vertical orientation of plyometric training on explosiveness performances and sprint force-velocity profile in young soccer players.Methods: Twenty-eight soccer players were recruited and divided in two groups: vertical (VG, n = 14) and horizontal (HG, n = 14) groups. Tests including jumps and sprint performances were conducted before and after the 8 week training period. Sprint force-velocity profile (FVP) was evaluated during a 30 m sprint test.Results: The results demonstrated significant improvements in both VG and HG for jump performances (from + 4.9% to + 9.0%), sprint times (from -5.5% to -8.7%) and FVP parameters. Higher relative changes for the HG than for the VG were observed in 5 m and 15 m sprint times, horizontal jump lengths, and also in FVP parameters, especially improvements in maximal power (VG: + 16.4% vs. HG: + 28.1%) and in the decrease rate of horizontal orientation of force with increasing speed (HG: + 22.9%) during the 30 m sprint.Conclusions: Both horizontal and vertical plyometric training can be either used in young soccer players to improve vertical and horizontal performances in jump and sprint. However, horizontal plyometric training may result in a greater improvement in horizontal ballistic actions while similarly developing vertical jump qualities compared to vertical plyometric training in young soccer players

Heterogeneity of energy metabolism within the tibialis anterior: is it just an outcome of a specific muscle activation, architecture and composition?

International audienc

Both vertical and horizontal plyometric training influence sprint force-velocity profile in young elite soccer players.

International audienceINTRODUCTION:During a soccer match, sprint horizontal acceleration ability is determinant for performance. Development of sprint force and velocity qualities has been reported after plyometric training (1). However, the orientation of plyometric training exercises can influence functional performance (2). The purpose of this study was to compare horizontal and vertical orientation plyometric training on explosiveness performance and sprint force-velocity profile in young soccer players.METHODS:Twenty-eight soccer players were recruited and divided in two groups: vertical group (VG, n = 14) and horizontal group (HG, n = 14). Tests including vertical and horizontal jumps (i.e., squat jump [SJ], countermovement jump and 30-cm drop jump [DJ]) and a 30-m sprint were conducted before and after the 8-wk training period. Sprint force-velocity profile (FVP) was evaluated during a 30-m sprint test.RESULTS:The results demonstrated significant improvements in both VG and HG for vertical jump performances (from +5.0% to +11.5%), horizontal jump performances (from +5.6% to +9.8%), sprint times (from -4.7% to -12.2%) and FVP parameters. Higher decrease in sprint performance for HG were found in 5-m (VG: -6.4% vs. HG: -12.2%) and 15-m (VG: -4.7% vs. HG: -8.6%) sprint times, horizontal DJ (VG: +5.8% vs. HG: +9.8%), but also in FVP parameters, especially the maximal power (VG: +16.4% vs. HG: +28.1%) and the horizontal orientation of force (VG: no significant difference vs. HG: +22.9%) during the 30-m sprint (P < 0.05).CONCLUSION:Both horizontal and vertical plyometric training can be either used in young soccer players to improve vertical and horizontal performances in jump and sprint as previously reported (3). However, horizontal plyometric training may give a larger gain in horizontal ballistic actions while developing vertical jump qualities in young soccer players. Further studies are necessary to more deeply compare motor coordination and muscular synergies involved in vertical and horizontal actions and potential specific effects on musculoskeletal structural adaptations

Is Branched-Chain Amino Acids Supplementation an Efficient Nutritional Strategy to Alleviate Skeletal Muscle Damage? A Systematic Review

International audienceAmino acids and more precisely, branched-chain amino acids (BCAAs), are usually consumed as nutritional supplements by many athletes and people involved in regular and moderate physical activities regardless of their practice level. BCAAs have been initially shown to increase muscle mass and have also been implicated in the limitation of structural and metabolic alterations associated with exercise damage. This systematic review provides a comprehensive analysis of the literature regarding the beneficial effects of BCAAs supplementation within the context of exercise-induced muscle damage or muscle injury. The potential benefit of a BCAAs supplementation was also analyzed according to the supplementation strategy-amount of BCAAs, frequency and duration of the supplementation-and the extent of muscle damage. The review protocol was registered prospectively with Prospective Register for Systematic Reviews (registration number CRD42017073006) and followed Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Literature search was performed from the date of commencement until August 2017 using four online databases (Medline, Cochrane library, Web of science and ScienceDirect). Original research articles: (i) written in English; (ii) describing experiments performed in Humans who received at least one oral BCAAs supplementation composed of leucine, isoleucine and valine mixture only as a nutritional strategy and (iii) reporting a follow-up of at least one day after exercise-induced muscle damage, were included in the systematic review analysis. Quality assessment was undertaken independently using the Quality Criteria Checklist for Primary Research. Changes in indirect markers of muscle damage were considered as primary outcome measures. Secondary outcome measures were the extent of change in indirect markers of muscle damage. In total, 11 studies were included in the analysis. A high heterogeneity was found regarding the different outcomes of these studies. The risk of bias was moderate considering the quality ratings were positive for six and neutral for three. Although a small number of studies were included, BCAAs supplementation can be efficacious on outcomes of exercise-induced muscle damage, as long as the extent of muscle damage was low-to-moderate, the supplementation strategy combined a high daily BCAAs intake (\textgreater200 mg kg(-1) day(-1)) for a long period of time (\textgreater10 days); it was especially effective if taken prior to the damaging exercise

Effect of hip and knee joint angles on resting hamstring muscles rigidity in men and women

Purpose: Hamstring muscle strains are one of the most common injuries in sports practice, for both men and women. However, sex disparities in the rate of muscle injuries have been observed. As these muscular injuries usually occur at long muscle length, this study aimed to determine the effect of sex on hamstring muscles' resting rigidity under different stretching conditions.Methods: The shear wave speed (SWS) of resting hamstring muscles was measured in 12 men and 12 women in different hip and knee positions (hip extended with knee flexed, hip flexed with knee extended, both joints extended and both joints flexed).Results: Combining all the positions, the SWS of the semitendinosus was higher in men than in women (2.96 vs. 2.71 m.s-1). Regardless of sex, a significant rise in SWS was systematically observed when the semimembranosus was stretched (1.86, 2.37, 2.76 and 4.39 m.s-1) but it was neither the case for the semitendinosus (p = 0.82) nor for the biceps femoris (p = 0.50). Finally, differences in SWS among the hamstring muscles were only observed at the longest muscle length, with greater SWS values for the semimembranosus and semitendinosus in comparison with the biceps femoris (4.39 and 4.12 vs. 3.38 m.s-1 respectively).Conclusion: In conclusion, a sex difference was only observed in the resting semitendinosus rigidity. Independently of sex, the increase in resting hamstring muscles SWS with stretch was muscle specific