The claim was about testosterone levels not muscle mass. It doesn't appear to be true that lifting has any impact on testosterone levels aside from the first h

The claim was about testosterone levels not muscle mass. It doesn't appear to be true that lifting has any impact on testosterone levels aside from the first hour after lifting. It goes up temporarily then returns to normal. It appears scientists have studied such things. The biological concept of homeostasis could explain why that might be true. So it is what it is.