Physical activity
Women gain the same strength and muscle mass as men in weight training
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MPH, MSc
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One thing that really surprises our students is that muscle mass growth in women is similar to that in men. Men have a larger body size than women, which means greater strength and greater muscle mass in absolute terms. However, how much muscle mass and strength increase with training is a different matter for each sex.
Studies show similar gains in muscle mass between men and women. Using ultrasonography and magnetic resonance imaging to measure muscle thickness and changes in muscle cross-sectional area, we found similar growth in the upper and lower limbs after weeks of training. Women even appear to gain more strength than men in the upper limbs.
We must understand the differences in results in absolute terms and in relative terms (each sex in relation to its body size). If a man with a muscle cross-sectional area of 40 cm and a woman with a muscle cross-sectional area of 30 cm begin training, and after a few months the man has 44 cm and the woman has 33 cm, the man has gained more in absolute terms (4 cm vs. 3 cm). However, in relative terms, both have increased their muscle mass by 10% (4 cm is 10% of 40, and 3 cm is 10% of 30). In other words, both have grown the same in proportion to their size.
It's not "testosterone"
Although men have about 10-15 times more testosterone than women at baseline, which rises to a sharp 45-fold difference with strength training, protein synthesis and anabolic markers are similar in men and women:
Protein synthesis rises similarly in men and women, both in response to exercise and in response to protein intake.
mTOR phosphorylation rises more in men than in women immediately after exercise, but p70S6K1 phosphorylation shows no major differences between the sexes.
This implies that there is no obvious connection between exercise-induced hormones, including testosterone, and shows that protein synthesis activation occurs with low systemic testosterone concentrations in women. However, there is a dimorphic effect of basal testosterone, being related to physiological levels with greater muscle mass in men, but not in women. In other words, men with higher testosterone levels have more muscle mass than men with lower levels of this hormone, but this effect is not as clear in women.
Conclusion
The relative growth in muscle mass in men and women with weight training is similar, and markers of protein synthesis and anabolic pathways are not very different between men and women.
As we have mentioned, this aspect surprises many people. There is likely to be a psychological and sociocultural influence. When thinking about the musculature of a prototypical "fitness" man, many of the mental images that come to mind correspond to men who have that physique because they consume hormones. Not only huge bodybuilders, but even the average model or sexy actor of the moment is highly likely to have used hormones to achieve such a defined physique, even if they are not huge. Prototypical "fitness" bodies are not the reality of the average man's body, but rather an unrealistic image of male musculature and physique. Therefore, there is a bias that overestimates the reality of male musculature.
Studies show similar gains in muscle mass between men and women. Using ultrasonography and magnetic resonance imaging to measure muscle thickness and changes in muscle cross-sectional area, we found similar growth in the upper and lower limbs after weeks of training. Women even appear to gain more strength than men in the upper limbs.
We must understand the differences in results in absolute terms and in relative terms (each sex in relation to its body size). If a man with a muscle cross-sectional area of 40 cm and a woman with a muscle cross-sectional area of 30 cm begin training, and after a few months the man has 44 cm and the woman has 33 cm, the man has gained more in absolute terms (4 cm vs. 3 cm). However, in relative terms, both have increased their muscle mass by 10% (4 cm is 10% of 40, and 3 cm is 10% of 30). In other words, both have grown the same in proportion to their size.
It's not "testosterone"
Although men have about 10-15 times more testosterone than women at baseline, which rises to a sharp 45-fold difference with strength training, protein synthesis and anabolic markers are similar in men and women:
Protein synthesis rises similarly in men and women, both in response to exercise and in response to protein intake.
mTOR phosphorylation rises more in men than in women immediately after exercise, but p70S6K1 phosphorylation shows no major differences between the sexes.
This implies that there is no obvious connection between exercise-induced hormones, including testosterone, and shows that protein synthesis activation occurs with low systemic testosterone concentrations in women. However, there is a dimorphic effect of basal testosterone, being related to physiological levels with greater muscle mass in men, but not in women. In other words, men with higher testosterone levels have more muscle mass than men with lower levels of this hormone, but this effect is not as clear in women.
Conclusion
The relative growth in muscle mass in men and women with weight training is similar, and markers of protein synthesis and anabolic pathways are not very different between men and women.
As we have mentioned, this aspect surprises many people. There is likely to be a psychological and sociocultural influence. When thinking about the musculature of a prototypical "fitness" man, many of the mental images that come to mind correspond to men who have that physique because they consume hormones. Not only huge bodybuilders, but even the average model or sexy actor of the moment is highly likely to have used hormones to achieve such a defined physique, even if they are not huge. Prototypical "fitness" bodies are not the reality of the average man's body, but rather an unrealistic image of male musculature and physique. Therefore, there is a bias that overestimates the reality of male musculature.
#physicalexercise #women
References:
Roberts BM, Nuckols G, Krieger JW. Sex Differences in Resistance Training: A Systematic Review and Meta-Analysis. J Strength Cond Res. 2020 May;34(5):1448-1460. https://doi.org/10.1519/JSC.0000000000003521
Abe T, DeHoyos DV, Pollock ML, Garzarella L. Time course for strength and muscle thickness changes following upper and lower body resistance training in men and women. Eur J Appl Physiol. 2000 Feb;81(3):174-80. https://doi.org/10.1007/s004210050027
West DW, Burd NA, Churchward-Venne TA, Camera DM, Mitchell CJ, Baker SK, Hawley JA, Coffey VG, Phillips SM. Sex-based comparisons of myofibrillar protein synthesis after resistance exercise in the fed state. J Appl Physiol (1985). 2012 Jun;112(11):1805-13. https://doi.org/10.1152/japplphysiol.00170.2012
Dreyer HC, Fujita S, Glynn EL, Drummond MJ, Volpi E, Rasmussen BB. Resistance exercise increases leg muscle protein synthesis and mTOR signalling independent of sex. Acta Physiol (Oxf). 2010 May;199(1):71-81. https://doi.org/10.1111/j.1748-1716.2010.02074.x
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