Recent theories claim that estrogen has a protective effect against muscle damage caused by exercise. For example, estrogen may prevent delayed onset muscle soreness, or DOMS, which is the pain and associated damage to the muscle tissues that often occurs after intense exercise. A recent study in the Journal of Strength and Conditioning Research investigated the effects of estrogen on muscle damage after intense eccentric exercise, specifically in relation to the phases of the menstrual cycle.

 

It isn’t immediately clear that this protective effect is necessarily a good thing. To some extent, muscle damage is a part of the process of muscle growth and strength building. However, since athletes everywhere are universally united in hating DOMS and looking for a way to recover faster from it, female athletes may have just such a way.

 

The menstrual cycle is broken up into two phases. The first phase is the follicular phase, which comprises approximately the first two weeks of the menstrual cycle. During the first part of the follicular phase, estrogen levels (and most other reproductive hormones, except FSH) are low. A dramatic and sudden spike in hormones occurs around the time of ovulation, after which is the luteal phase. Hormonally speaking, the reverse of the follicular phase occurs, and body temperature tends to be higher.

 

Breaking Muscle Shop

 

According to the hypothesis proposed by the researchers, if estrogen has a protective effect on muscles, we would find reduced damage during the luteal phase. The research team used traditional DOMS markers to measure damage, such as soreness and muscle swelling, as well as other markers like creatine kinase, an enzyme that is a marker for muscle damage.

 

The researchers chose a group of women and assigned them randomly to either a luteal or follicular group. The women came back to exercise sometime during the first few days of each of these phases. The participants did intense eccentric exercise designed to create muscle soreness. They then came back for five of the following seven days to test muscle damage.

 

The results were the opposite of what the researchers expected. The group in the high estrogen phase had worse recovery of strength after the eccentric exercise. Conversely, those in the low estrogen phase had faster recovery of strength. And, when estrogen was high, so was circulating creatine kinase. All of the other markers for muscle damage were roughly the same.

 

There is a possible answer for these results. The researchers believe it might be true that the estrogen levels present during exercise recovery are more important than the levels at the time the exercise occurs. While this may sound like an excuse for why the results went against what was hypothesized, it does make some sense. The luteal group would have had declining estrogen levels during the recovery week, while the follicular group would have had rising estrogen levels.

 

More information is needed on the protective effects of estrogen on exercise. While it turns out that estrogen doesn’t prevent the damage from occurring in the first place, it’s possible that it helps speed up recovery of muscle tissue. While the jury is still out on this topic, in the meantime it seems best for women to hit the hardest workouts during the follicular phase.

 

References:

1. Melissa Markofski, et. al., “Influence of menstrual cycle on indices of contraction-induced muscle damage,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000429

 

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