Muscle strength – we think of testosterone as being the strength and bodybuilding hormone. Yes, testosterone DOES promote muscle growth and strength development by boosting muscle protein synthesis. Yet, women have far lower levels of testosterone relative to men. The reason women have testosterone at all is that their ovaries and adrenal glands produce a small amount. In contrast, most testosterone production in men comes from the testicles.
In contrast to men, women have ovaries that produce estrogen. It’s estrogen that gives women their distinctively female characteristics, larger breasts, smaller waist size, and wider hips. Estrogen is also important for fertility and menstrual cycle regularity and for the preservation of bone mass. Prior to menopause, estrogen levels vary with the menstrual cycle, dropping to the lowest level just prior to menstruation. After menopause, estrogen production by the ovaries ceases.
Estrogen and Muscle Strength Gains
Since estrogen plays a role in preserving healthy bones, you might wonder whether it plays a role in muscle strength gains and in muscle growth in response to resistance training. When men experience a drop in testosterone with age, their strength also declines along with it. Is this also true in women? What role does estrogen play in muscle strength and in loss of muscle strength and size with age?
As you know, both men and women lose muscle size and strength with age, and in women loss of muscle strength accelerates after menopause, corresponding to the time that estrogen levels drop. Interestingly, women and men have roughly similar muscle strength in the legs, when you take into account differences in muscle size, but this changes after menopause as women lose strength at a faster rate. Since estrogen is produced by the ovaries and the ovaries stop functioning after menopause, it’s easy to see why women are estrogen deficient after menopause. Even after menopause, most women produce some estrogen since testosterone produced by the adrenal glands can be converted into estrogen.
That’s not the only evidence suggesting estrogen plays a role in muscle strength – women who take estrogen-based hormone replacement therapy do not experience the same degree of strength loss after menopause as women who approach menopause naturally. Plus, studies in rodents show mice who have had their ovaries removed have leg muscles that are 10 to 20% weaker than mice who retain their ovaries and ability to produce estrogen.
Research suggests that estrogen enhances the ability of muscles to generate force not by increasing the size of the muscle but by improving the QUALITY of the muscle tissue, possibly by its effect on the muscle protein myosin. Myosin is one of the two proteins, actin being the other, that’s directly involved in muscle contraction. Surprisingly, at least one study shows estrogen DECREASES tendon strength.
Does Estrogen Enhance Muscle Recovery?
After a strength-training workout, muscles need time to recover. That’s why you shouldn’t work the same muscle group for at least 48 hours. During the rest and recovery period between workouts, muscles go through a repair process that’s important for muscle growth. Interestingly, estrogen seems to reduce the amount of muscle damage that occurs in response to a workout. How might it do this?
According to research, estrogen acts as an antioxidant, which helps reduce muscle inflammation. It also helps stabilize muscle cell membranes. If that’s the case, you might think having more estrogen would limit muscle growth since muscle damage is one stimulus for hypertrophy. Based on current research, there’s no evidence that estrogen stimulates or interferes with muscle growth, only that it helps prevent muscle atrophy and preserve muscle strength.
One way it seems to preserve muscle strength and size is by activating satellite cells. These are cells that are directly involved in strength gains and hypertrophy. In response to the stress of training, satellite cells fuse with muscle cells and donate their own nuclei and contractile proteins to the cells, giving them the ability to contract with greater force. You might also expect this to be a stimulus for muscle growth.
Bodybuilding and Estrogen
Despite evidence that estrogen helps preserve strength and prevent muscle atrophy, most male bodybuilders want to reduce the influence estrogen has on their physique. Remember, men have some estrogen circulating in their body, primarily because fat cells contain an enzyme called aromatase that converts testosterone to estrogen. Men who have a higher body fat percentage generally produce more estrogen since they have more fat cells.
At high levels, estrogen can promote breast enlargement, but male bodybuilders also have the mistaken idea that estrogen itself increases body fat. In reality, estrogen does not contribute to fat gain, although having a higher estrogen level can lead to fluid retention that makes a toned body look “softer.” The reason men who have more estrogen are “fatter” is that they have more fat cells to make estrogen and estrogen increases water weight.
The Bottom Line
Estrogen does appear to play a role in preserving strength. Plus, it enhances muscle recovery and may be modestly beneficial for muscle hypertrophy, or at least, preserving muscle size because it activates satellite cells. Although the drop in estrogen women experience after menopause may explain why we lose strength more rapidly after age 50, other anabolic hormones, like growth hormone, also decline and are likely contributors to the loss of lean body mass.
What this means is strength training is even more important after menopause since you lose muscle strength and size naturally as you make less estrogen and as other anabolic hormones drop. As you experience the loss of muscle mass, a cascade of events occurs that makes it harder to maintain a healthy body weight and body fat percentage.
With less muscle, insulin resistance becomes more of a problem and your resting metabolic rate slows as well. So often you hear about the importance of aerobic exercise for healthy aging but there’s still too little emphasis on strength training. Strong muscles are what help you conserve a high level of functioning during mid-life and after. Make sure you’re doing it regularly.
References:
Exerc Sport Sci Rev. 2010;38(2):61-67.
Eurasian J Med. 2011 Aug; 43(2): 109-114. doi: 10.5152/eajm.2011.24.
Wolf, Megan R., “Effects of Estrogen on Muscle Damage in Response to an Acute Resistance Exercise Protocol” (2009). Honors.
“Hormones and Resistance Exercise.” By Derek Marks, M.S., and Len Kravitz, Ph.D.
Journal of Strength and Conditioning Research, 14(2), pp 220-227.
“How do muscles grow?” Young sub Kwon, M.S. and Len Kravitz, Ph.D.
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Why It Becomes Harder to Build Muscle Over Time
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4 Reasons We Lose Strength as a Result of Loss of Muscle as We Age
