The muscle morphology of sprinters

The ability to sprint fast and jump high are important abilities for athletes in a variety of sports. Currently there is a lack of research investigating the muscular characteristics important for sprinting and jumping. Therefore, the aims of this thesis were to: comprehensively assess the importance of lower body muscle volumes (measured by magnetic resonance imaging) for sprint performance within both male and female sprinters, by comparing groups of different performance standards and examining the relationships with season’s best race time; compare muscle volumes between male and female sprinters, and also between sub-groups of elite males, elite females, and performance matched (to elite females) sub-elite males; and assess the relationships between muscle volumes and vertical jump performance (jump height). Chapter III revealed pronounced anatomically-specific differences in muscle volumes between groups of elite male sprinters, sub-elite male sprinters and untrained males; absolute and relative total lower body muscularity differentiated elite from sub-elite sprinters, with the hip extensor muscle group in particular exhibiting the largest differences / relationships (elite, +32% absolute, +15% relative [per kg body mass] volume vs. sub-elite, and explaining 31-48% of the variability in sprint performance across the whole male sprint cohort). Chapter IV found that in females, total lower body absolute muscle volume was larger in elite than sub-elite sprinters (+15%). Elite female sprinters had larger volumes of the hip flexors (absolute +28%, relative +19%), hip extensors (absolute +22%, relative +14%) and knee extensors (absolute +21%), with relative hip flexor volume alone explaining 48% of sprint performance variability across the whole female cohort. Chapter V documented male sprinters being significantly more muscular than females, but in an anatomically specific pattern (i.e. differences in hip extensors and flexors > knee flexors and extensors > plantarflexors). Notably, this chapter provided novel evidence that muscle volume may be the primary explanatory variable for the sex difference in sprint performance, and indicated a distinct muscular distribution common to elite sprinters, irrespective of sex. Chapter VI highlighted the particular importance of knee extensor muscle volumes for countermovement jump performance, where the vastus medialis alone explained 14% of the variance in jump height. In conclusion, this thesis provides the first comprehensive description of lower body muscle volumes in elite sprinters, and provides novel evidence illustrating the importance of overall lower body muscularity, but particularly the anatomical distribution of that muscularity (specifically relative volumes of the hip extensors for males, and the hip extensors and flexors for females, as a determinant of sprint performance.