Sex-based differences in skeletal muscle kinetics and fiber-type composition

Abstract

Previous studies have identified over 3,000 genes that are differentially expressed in male and female skeletal muscle. Here, we review the sex-based differences in skeletal muscle fiber composition, myosin heavy chain expression, contractile function, and the regulation of these physiological differences by thyroid hormone, estrogen, and testosterone. The findings presented lay the basis for the continued work needed to fully understand the skeletal muscle differences between males and females.

FIGURE 1.

Type-IIa fibers are differentially expressed in male vs. female hindlimb muscle sections and in different muscle bodies In the soleus, IIa expression is 58% in the male 36% in the female. In the plantaris, IIa expression is16% in the male and 37% in the female. In the tibialis anterior muscle, IIa expression is 39% in the male and 25% in the female. Green staining identifies IIa fibers, whereas red staining identifies IIb fibers. Figure was generously provided by Brooke Harrison, PhD.