Muscle mass gains seem to differ quite a lot between individuals. How variable are muscle mass gains?
This study assessed muscle growth in the biceps for 585 participants (342 women, 243 men) during 12 weeks of resistance training. Subjects trained only one arm, so the other arm could serve as a control. Bicep muscle cross-sectional area was measured with MRI in both arms.
As expected, muscle growth differed quite a lot between subjects. The worst gainers did not grow any muscle at all, while the best gainers increased muscle size with more than 50% (for both men and women). However, most people had average results.
Despite it is commonly believed that women gain substantially less muscle compared to men, the men only had a very slight advantage for relative muscle gain (20% vs 18%).
This study cannot determine why the muscle mass gains were different. Both differences in lifestyle (diet, sleep, stress, etc) and genetics are likely to play a role.
PS: what do you think would happen in the long term? Would individuals with lower initial gains catch up in the long term or are doomed with a lower potential to gain muscle mass (a lower muscle mass limit)?
Go to the next post in the resistance exercise series:
Calf muscles have a poor growth response?
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