Muscle-Fiber Typology Is Associated With Sprint-Cycling Characteristics in World-Class and Elite Track Cyclists

Purpose: Identifying the determinants of performance is fundamental to talent identification and individualizing training prescription. Consequently, the aim of this study was to determine whether estimated muscle typology is associated with the key mechanical characteristics of track sprint cycling. Methods: Sixteen world-class and elite track cyclists (n = 7 female) completed a laboratory session wherein torque-cadence and power-cadence profiles were constructed to determine maximal power output (Pmax), optimal cadence (Fopt), and maximal cadence (Fmax), and fatigue rate per pedal stroke was determined during a 15-second maximal sprint at Fopt. Muscle typology was estimated by measuring carnosine content via proton magnetic resonance spectroscopy in the gastrocnemius and soleus. Results: Using partial correlation analysis to account for sex, greater muscle carnosine content (ie, greater estimated proportion of type II fibers) was associated with a greater Pmax (r= .68, P= .007), Fmax (r = .77, P= .0014), Fopt (r = .61, P = .0196), and absolute fatigue rate (W<middle dot>stroke-1; r = -.55, P = .0418) but not relative fatigue rate (%peak power<middle dot>stroke-1; r = -.33, P=.246). Conclusions: The findings from this study substantiate the mechanical differences in muscle-fiber types derived from single musclefiber studies and highlight the importance of estimated muscle typology for sprint cycling performance.