In vivo maximal fascicle-shortening velocity during plantar flexion in humans

Abstract

Interindividual variability in performance of fast movements is commonly explained by a difference in maximal muscle-shortening velocity due to differences in the proportion of fast-twitch fibers. To provide a better understanding of the capacity to generate fast motion, this study aimed to 1) measure for the first time in vivo the maximal fascicle-shortening velocity of human muscle; 2) evaluate the relationship between angular velocity and fascicle-shortening velocity from low to maximal angular velocities; and 3) investigate the influence of musculo-articular features (moment arm, tendinous tissues stiffness, and muscle architecture) on maximal angular velocity. Ultrafast ultrasound images of the gastrocnemius medialis were obtained from 31 participants during maximal isokinetic and light-loaded plantar flexions. A strong linear relationship between fascicle-shortening velocity and angular velocity was reported for all subjects (mean R 2 ϭ 0.97). The maximal shortening velocity (V Fmax) obtained during the no-load condition (NLc) ranged between 18.8 and 43.3 cm/s. V Fmax values were very close to those of the maximal shortening velocity (V max), which was extrapolated from the F-V curve (the Hill model). Angular velocity reached during the NLc was significantly correlated with this V Fmax (r ϭ 0.57; P Ͻ 0.001). This finding was in agreement with assumptions about the role of muscle fiber type, whereas interindividual comparisons clearly support the fact that other parameters may also contribute to performance during fast movements. Nevertheless, none of the biomechanical features considered in the present study were found to be directly related to the highest angular velocity, highlighting the complexity of the upstream mechanics that lead to maximalvelocity muscle contraction. maximal unloaded velocity; muscle-tendon unit; muscle mechanics; muscle architecture; stiffness; ultrasound THE CAPACITY OF HUMAN SKELETAL muscle to achieve maximal power production is functionally very important during ballistic movements such as sprinting or jumping. The maximal angular velocity an individual can produce represents one of the key determinants of this ability and hence of human performance in various explosive tasks such as a sprint while running or cycling (31, 57). In the literature, this ability to reach extreme angular velocities in unloaded conditions is related mainly to a higher proportion of fast-twitch fibers (5, 11, 56) or a longer fascicle length, or both, which implies a higher number of sarcomeres in series (9, 53). These considerations suggest that subjects who are able to produce high velocity at the joint level should also be able to develop high muscle fascicle-shortening velocity. Consequently, the muscleshortening velocity should be a key determinant of the ability to perform very-high-velocity movements.To our knowledge, no previous study has measured actual maximal fascicle-shortening velocity in vivo in humans. Although measurement of fascicle-shortening velocity is classically performed using ul...

Muscle fascicle shortening behaviour of vastus lateralis during a maximal force–velocity test

“…Contrary to the results obtained for plantar flexions, according to these authors, the muscle fascicle shortening velocity plateaued for joint velocities above 240° s −1 , suggesting an increase in the tendinous tissues contribution with the increase in knee extension velocity (up to 90% at 500° s −1 ). The discrepancy with the results obtained by Hauraix et al (2013Hauraix et al ( , 2015 on plantar flexor muscles could reflect different muscle fascicles-tendon interactions, according to the joint tested (ankle vs. knee), which may be associated with different mechanical tendon properties. In addition, De Brito Fontana et al (2014) measured the mean muscle fascicle shortening velocity during the entire motion, including acceleration as well as isokinetic and deceleration phases, while Hauraix et al (2013Hauraix et al ( , 2015 continuously tracked muscle fascicle during the movement to appraise the "instantaneous" muscle fascicle shortening velocity.…”

“…The discrepancy with the results obtained by Hauraix et al (2013Hauraix et al ( , 2015 on plantar flexor muscles could reflect different muscle fascicles-tendon interactions, according to the joint tested (ankle vs. knee), which may be associated with different mechanical tendon properties. In addition, De Brito Fontana et al (2014) measured the mean muscle fascicle shortening velocity during the entire motion, including acceleration as well as isokinetic and deceleration phases, while Hauraix et al (2013Hauraix et al ( , 2015 continuously tracked muscle fascicle during the movement to appraise the "instantaneous" muscle fascicle shortening velocity. Considering that (1) the respective contributions of muscle fascicles and tendinous tissues are highly dependent on the range of motion considered during the movement (Hauraix et al 2013), and the fact that (2) ultrasound data were sampled at very low frequencies (42-49 Hz, which is not recommended in the study of fast movements, Cronin and Lichtwark 2013), the chosen methodological approach may strongly influence the subsequent results and potentially explain the observed differences.…”

“…After each extension, the knee was passively placed in starting position. The previous studies showed higher maximal joint velocity during unloaded plantar flexions performed with preactivation (1325° s −1 , Farcy et al 2014) compared to without pre-activation (701° s −1 , Hauraix et al 2015). However, the maximal fascicle shortening velocity was much higher without pre-activation (23.2 cm s −1 compared to 34.7 cm s −1 ).…”

“…Subsequently, when the contraction starts and after a possible additional slight lengthening of tendinous tissues induced by shortening of muscle fascicles, the elastic tendinous tissues are, in turn, shortened, contributing significantly to the shortening velocity of the muscle-tendon unit (up to 46%). Interestingly, during these maximal concentric contractions, the respective contributions of muscle fascicles and tendinous tissues to muscle-tendon unit shortening velocity did not change with the movement velocity from slow plantar flexions (30° s −1 ) up to maximal joint velocity (Hauraix et al 2013(Hauraix et al , 2015.…”

“…Muscle fascicles-tendon interactions are also involved in concentric contractions of the knee extensors (De Brito Fontana et al 2014;Finni et al 2003;Ichinose et al 2000) and plantar flexors (Chino et al 2008;Hauraix et al 2013Hauraix et al , 2015Randhawa et al 2013). For instance, during a maximal plantar flexion, the initial ankle dorsiflexion position induces stretching of the muscle-tendon unit and hence of the tendinous tissues before the contraction (Hauraix et al 2013).…”