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...

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 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 muscles in different ways.

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.

If you switch up your leg exercises during a workout routine, you might build more muscle in certain parts of your thigh—like the upper side—compared to sticking with the same moves.

If young guys who haven't worked out in a while do different leg exercises for 9 weeks, their upper outer thigh muscles grow more than the middle part — even with exercise variety, growth isn't even.