One of my older buddies, a 74-year-old, fitness-conscious fellow, when asked how heâ??s doing, often responds, â??Iâ??m keeping it tight,â?* which always gives people a laugh. Amusing as it is to hear the phrase coming out of a septuagenarianâ??s mouth, his goal of keeping trim, with as much muscle as possible, is a serious one â?? and one we all should shoot for, ** matter what age we are. The challenge with muscle mass is that after the age of 40, it starts to decline at roughly 1% a year.