The least likely explanation for this would be that they're training at different intervals, or one is training harder than the other.
The most likely reason is that the way the other person's genetics are most people cant gain muscle as well as others because of disease or their body structure.
Hope this helped!
Large amount of paper on a bulletin board.
a young girl lives at home with her obese mother. her mother seldomly cooks and when she does it's not healthy. she spends her days watching cartoon and snacking on chips and candies. when she goes to her next doctors appointment, she is informed that she is obese for her age and is at very high risk for diabetes.
on the other side of town there is a young boy who has not even begun puberty. his father is a champion bodybuilder and his mother is a yoga enthusiast. his father believes the earlier you start them on weights the better. he is shorter than the other boys his age but has much more muscle mass. when he visits the doctor, the doctor tells him he is in the lowest percentile for height.
Might wanna reword the question
