Muscle fibre type, efficiency, and mechanical optima affect freely chosen pedal rate during cycling

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Abstract
This study investigated the variation in freely chosen pedal rate between subjects and its possible dependence on percentage myosin heavy chain I (%MHC I) in m. vastus lateralis, maximum leg strength and power, as well as efficiency. Additionally, the hypothesis was tested that a positive correlation exists between percentage MHC I and efficiency at pre‐set pedal rates but not at freely chosen pedal rate. Twenty males performed cycling at low and high submaximal power output (∼40 and 70% of the power output at which maximum oxygen uptake (VO2max) was attained at 80 r.p.m.) with freely chosen and pre‐set pedal rates (61, 88, and 115 r.p.m.). Percentage MHC I as well as leg strength and power were determined. Freely chosen pedal rate varied considerably between subjects: 56–88 r.p.m. at low and 61–102 r.p.m. at high submaximal power output. This variation was only partly explained by percentage MHC I (21–97%) as well as by leg strength and power. Interestingly, %MHC I correlated significantly with the pedal rate at which maximum peak crank power occurred (r = −0.81). As hypothesized, %MHC I and efficiency were unrelated at freely chosen pedal rate, which was in contrast to a significant correlation found at pre‐set pedal rates (r = 0.61 and r = 0.57 at low and high power output, respectively). Conclusions: Subjects with high percentage MHC I chose high pedal rates close to the pedal rates at which maximum peak crank power occurred, while subjects with low percentage MHC I tended to choose lower pedal rates, favouring high efficiency. Nevertheless, the considerable variation in freely chosen pedal rate between subjects was neither fully accounted for by percentage MHC I nor by leg strength and power. Previously recognized relationships between percentage Type I (∼%MHC I) and efficiency as well as between pedal rate and efficiency were confirmed for pre‐set pedal rates, but for freely chosen pedal rate, these variables were unrelated.