These days, weight training is almost as popular as women as it is with men. Yes, more women are grabbing heavier weights and pushing their training as a way to grow leaner, stronger, and more defined. No longer is the goal to be skinny. It’s more important to look healthy and perform at a higher level. Weight training for both genders is here to stay. Plus, weight training builds confidence and self-esteem. It’s a physical and mental sport!
With the growing popularity of strength training among both sexes, you might wonder whether there are differences in how men and women gain strength and muscle size. First, men have a higher percentage of muscle relative to women. On average, when you compare muscle mass between men and women, women have about 2/3 the muscle mass than men do and those differences extend to strength as well. In terms of raw strength, women are about half as strong as men in the upper body and 66% as strong in the lower body.
How can you explain this gender difference? Research carried out by the National Strength and Conditioning Association shows, overall, women have about two-thirds the total muscle mass than men do, and females are able to generate about two-thirds the force that males can. This suggests that differences in strength between the two sexes are related to variations in muscle mass and body size. The strength differential is strongest for the upper body since women have less muscle on their upper body than their lower body and significantly less than a man.
Women Can Build Muscle Too!
But we know males and females can both increase the size of their muscles and become stronger through resistance training. A woman’s muscles will grow in response to training just as a man’s will. Muscles increase in size when muscle fibers are exposed to more load than they’re accustomed to. In response to the overload, the muscles adapt and become larger and more capable of handling the extra force. They do this partially by the muscle fibers laying down new contractile elements. This makes the muscle fibers thicker and also increases their ability to generate force. Both men and women also gain strength through neurological adaptations whereby the nervous system becomes more efficient at telling the muscles to contract.
What about hormonal differences between the two sexes? We know that men have higher levels of the anabolic hormone testosterone. In fact, men have ten times the quantity of testosterone circulating in their bloodstream relative to women. An exception is women with polycystic ovarian syndrome (PCOS). A woman with PCOS can have significantly higher levels of testosterone than the average woman. Despite lower levels of testosterone, women gain strength and muscle size, even without the benefit of high levels of testosterone.
How are women able to gain muscle size yet be so testosterone deficient? Testosterone isn’t the only anabolic hormone that drives muscle growth. Growth hormone, released from the posterior pituitary gland in the brain, does too. Studies show that women have higher levels of circulating growth hormone relative to men and this may partially explain why women and men have similar responses to training despite variations in hormones.
The Role of Estrogen
Women have higher levels of the female sex hormone estrogen relative to men. Having higher levels of estrogen has pros and cons with regard to body composition. Estrogen partially explains why women have greater body fat percentage than men, as estrogen influences where fat is stored. Before menopause, higher levels of estrogen means greater fat storage around the hips and thighs. After menopause, a drop in estrogen shifts fat storage away from the thighs and hips and toward the middle of the body, around the belly. Less appreciated is the anti-catabolic effects of estrogen. While estrogen isn’t an anabolic hormone, like testosterone, it helps protect against muscle breakdown during exercise. So, it indirectly helps with muscle mass preservation. It’s no coincidence that you lose muscle mass faster after menopause as estrogen levels drop.
Differences in Muscle Fiber Types
Muscle fibers are divided into two main types: Type 1, or slow-twitch muscle fibers, and type 2, or fast-twitch. The latter fibers are optimized for generating strength and power while the former is called into play more for endurance exercise. Men tend to have a higher ratio of fast-twitch fibers relative to women. The greater percentage of slow-twitch fibers that women have gives the female gender an advantage when doing high-volume training. Women can handle more training volume and, thanks to estrogen, don’t experience as much muscle breakdown when they boost their volume of training. So, women have some advantages over men from a training perspective.
The downside? Due to hormonal limitations, women have to work harder than men to build muscle mass. Some women use lighter weights for fear of bulking up, but there’s a greater likelihood that they’ll experience a minimal change to their body composition using this approach. To see significant change, the average woman needs to work with heavier resistance and perform greater total volume relative to a man. This is especially true of the upper body where women are at a greater strength disadvantage.
If you’re a female, you can also benefit from including more compound, multi-joint exercises in your routine, including deep squats, deadlifts, and bench press. Yet, these are exercises that some women shy away from. Don’t be one of them!
The Bottom Line
Women build strength and muscle size in the same way that men do. It all comes down to using progressive overload to force the muscles to adapt and become thicker and stronger. Yet, women start out with lower muscle mass than men and have a hormonal structure that’s not as conducive to muscle growth. So, women should focus on using a weight that challenges the muscles and on training volume. Beyond training, it’s important to get enough protein and maintain a slight calorie surplus to optimize muscle hypertrophy.
· Eur J Appl Physiol Occup Physiol. 1993;66(3):254-62.
· American Council on Exercise. “Building Muscle for Women”
· Clin Chem, 44(6). (p. 1289-1295).
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