A new study funded in part by the NIA funded Pepper Center at UTMB looked at whether natural changes in estrogen levels during the menstrual cycle influence how women’s muscles respond to exercise and protein.  Dr. Andrew Murton and colleagues compared muscle protein synthesis — the process that helps muscles repair and grow — during two phases of the cycle: the early follicular phase (when estrogen is low) and the late follicular phase (when estrogen is high).

Seventeen healthy women completed resistance exercise and drank an amino‑acid supplement while scientists measured how their muscles responded. Despite big differences in estrogen levels between the two phases, the rate of muscle protein synthesis didn’t change.

Interestingly, some genes linked to muscle building were more active during the high‑estrogen phase, but this didn’t translate into actual increases in muscle protein production. The study also found moderate links between testosterone levels (not estrogen) and muscle‑building activity.

Bottom line: Even though estrogen influences many body systems, it doesn’t appear to play a major role in short‑term muscle growth after exercise in women with regular menstrual cycles.