Size of Biceps Femoris Long Head Muscle Is Related to Running Economy in Male Recreational Runners.

Although the hamstring muscles play an important role in running, very little is known about the individual contributions of each hamstring muscle (biceps femorislong head, biceps femorisshort head, semitendinosus, and semimembranosus) toward running economy. As such, our study examined all the muscles in the hamstring to provide insight into which muscles contribute the most to running economy. Such information can provide insight in designing precise exercise training programs for enhancing running performance. Secondary analysis from our cross-sectional study conducted on 23 male recreational runners examined the relationships between stretch shortening cycle potentiation (via leg press throw), running net VO2 (inverse of running economy) (at 11.3 km/h), and maximum cross-sectional area of biceps femorislong head, biceps femorisshort head, semitendinosus, and semimembranosus was assessed via magnetic resonance imaging. We obtained significant correlations between the maximum cross-sectional area of the biceps femorislong head and log10running net VO2 (r = -0.52; p < 0.05). Our multiple regression model showed that the maximum cross-sectional area of biceps femorislong head but not stretch shortening cycle potentiation predicted log10running net VO2 (r = -0.52; p < 0.01). We found no other relationship between any other hamstring muscles and log10running net VO2. Our findings provide preliminary evidence of the importance of the biceps femorislong head toward running economy. This may be due to the preferential activation of efficient slow twitch muscle fibers of the biceps femorislong head. Additionally, we noted that the biceps femorisshort head, semitendinosus, and semimembranosus muscles were not related to running economy in recreational male runners.