Gender differences in FFM accumulation and architectural characteristics of muscle

Purpose: The purpose of this study was to gain insight into the skeletal muscle development potential in women and to evaluate the contribution of muscle pennation angle (PANG) and fascicle length to gender differences in muscle size or FFM accumulation. Methods: Skeletal muscle architectural characteristics and FFM were studied in 29 strength-trained female and 22 age- and height-matched male college athletes. Muscle thickness (MTH) was measured by B-mode ultrasound at 13 anatomical sites. Isolated MTH and PANG of the triceps long head (TL), vastus lateralis (VL), and gastrocnemius medialis (MG) muscles were measured in vivo , and fascicle length was estimated. Results: Six female athletes had more than 60 kg of FFM, with the largest being 82.1 kg. In general, male athletes had a significantly greater FFM and MTH at all sites except for the anterior thigh. Isolated MTH and PANG of, the TL, VL, and MG were greater in males. There were no gender differences in limb length or fascicle length of the three isolated muscles. A significant correlation was observed between MTH and PANG for TL (r = 0.84) and MG (r = 0.41), but not for VL. Conclusions: In contrast to previous estimates, we conclude that the theoretical upper limit of FFM accumulation and FFM-to-height ratio in women is greater than 80 kg and 0.44 kg cm(-1), respectively. Gender differences in PANG appear to be related to differences in muscle size (MTH) and do not appear to contribute independently to the gender difference in FFM.