In older men who cycle for 12 weeks, some muscles increase in size while others do not, and the amount of change differs widely between people. This suggests that aerobic exercise affects different...

In older men, doing aerobic cycling for 12 weeks does not lead to measurable changes in the size of key lower leg muscles, including the calf and shin muscles.

In older men, doing 12 weeks of aerobic cycling may lead to slightly smaller muscles in certain parts of the upper leg, such as the back of the thigh and inner thigh, compared to others, which could indicate uneven muscle development.

After 12 weeks of cycling exercise, older men experienced increases in the size of two upper leg muscles but no change in seven other lower leg muscles, showing that the exercise affected some muscles more than others.

When you’re just starting out, how much total work you do matters more than how long you rest between sets—your muscles grow and get stronger either way.

If older people who didn’t get stronger from doing just one set of weight exercises start doing four sets instead, they’ll likely grow bigger muscles in their thighs after 10 weeks of working out twice a week.