Date Published: March 8, 2019
Publisher: Public Library of Science
Author(s): Andrea Monte, Paola Zamparo, Carlos Balsalobre-Fernández.
In this study we investigated the relationships between muscle-tendon parameters and average/peak values of velocity, force and power in sprint running focusing on the acceleration phase. Eighteen male sprinters (100 m PB: 10.66±0.51 s) participated to the study. Instantaneous values of horizontal velocity (v) were recorded by means of a radar and instantaneous values of force (F) and power (P) were calculated based on these data. Muscle thickness, fascicle length and pennation angle of knee extensors and plantar flexors, as well as Achilles tendon length and CSA, were measured by means of ultrasonography. In the first 20 m of the sprint average and peak speed were 6.31±0.59 and 8.88±0.98 m·s-1, respectively; force was highest at the start of the sprint (Fpeak = 10.02±1.43 N·kg-1) and power peaked about 1 s after the start (26.64±5.99 W·kg-1). Muscle-tendon parameters showed stronger correlations with peak values of power (R range: 0.81–0.92), force (R range: 0.56–0.84) and speed (R range: 0.53–0.85) than with average values of velocity over the 20 m distance (R range: 0.41–0.61) (R <0.47 = NS; R >0.71 = P < .001). These data underline that the influence of muscle tendon parameters on sprint performance could be better appreciated when peak values of power can be calculated rather than by considering the simple measure of average velocity (e.g. distance/time).
Sprint performance (e.g. in a 100 m race) is determined by the ability to accelerate rapidly, by the magnitude of maximal velocity and by the ability to maintain this velocity up to the end of the race ; the ability to accelerate rapidly in the first steps of a sprint is what separates an elite sprinter from a merely good one ; indeed, best sprinters exert larger propulsive forces (relative horizontal impulses) in the sprint running acceleration phase [3,4,5]. The ability to accelerate is a key parameter also in many team sports and the goal of many training programs.
The mean values and standard deviations of the muscle-tendon parameters are reported in Table 1.
In this study the relationship between muscle-tendon parameters and force/power production during the sprint running acceleration phase (in the first 20 m) was investigated; we observed that muscle thickness and relative fascicle length, as well as Achilles tendon CSA and length, are positively correlated with sprint running performance (with values of v, F and P) while pennation angle is negatively correlated with it.
The findings of this study improve our understanding of the interplay between muscle-tendon characteristics and sprint performance: the stronger correlations are observed between muscle-tendon parameters and peak power output and this suggests that considering/measuring this parameter: i) could allow to better understand the relationship between musculoskeletal morphometry and sprinting ability; ii) could allow to better understand the interplay between all these factors in determining sprint performance and iii) could increase the possibility to detect significant training induced changes.