The best way to improve leg strength would be to use a combination of cardio activities (walk/run) and lifting exercises such as squats, lunges and leg press/curls.
Building strength requires doing anaerobic exercises, for the legs that would mean doing squats or leg press with weights you can only do 5 or 6 repetitions and sprinting.
Following are the best ways to improve the leg strength:
1. Morning Wailk/Running : Regular morning walk for old and running is for youngsters. 2. Auyrvedic Massage