Abstract
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).
Highlights
Sprint performance 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 [1]; the ability to accelerate rapidly in the first steps of a sprint is what separates an elite sprinter from a merely good one [2]; best sprinters exert larger propulsive forces in the sprint running acceleration phase [3,4,5]
Force and power were not directly measured but calculated based on values of horizontal speed. This is a limitation of this study; this analysis allowed us to get a better insight on the determinants of sprint performance in comparison with previous studies where only the average speed over the 100 m distance was taken into consideration
Our findings indicate that the correlation coefficients of the relationships between muscle-tendon parameters and sprint performance largely improve when peak values of v, F and P in the acceleration phase are considered (R range: 0.62–0.92), peak power and τ being the parameters best correlated with muscle-tendon proprieties (R range: 0.73–0.96)
Summary
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 [1]; the ability to accelerate rapidly in the first steps of a sprint is what separates an elite sprinter from a merely good one [2]; best sprinters exert larger propulsive forces (relative horizontal impulses) in the sprint running acceleration phase [3,4,5]. As an example Rabita et al [6] have shown that, in the first 30 m of a 100 m race the increase in running velocity is mirrored by a decrease in horizontal force; as a result, power output, which is recognized to be the major determinant of sprint performance and acceleration ability [5,6,7], is maximal in the first steps of a sprint. Force, velocity and power are influenced by fibre type distribution and architecture: i) fast contracting fibres can shorten up to 2–3 times faster than slow contracting ones; ii) muscles with larger cross sectional area (CSA) generate larger tensions and peak isometric forces (this is, as an example, the case of pennate muscles); iii) muscles with (relatively) longer fibres (e.g. fusiform, non-pennate, muscles) can contract more rapidly and generate peak power at a higher velocity [8,9,10,11,12,13]
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