A variety of activities can be traded with walking and running. Indoor and outdoor cycling help build strong quadriceps. Competitive soccer builds muscle power and speed. Aquarunning and aquawalking are very good for injured people. Make water workouts feel at least as vigorous as land workouts.
Stair climbing improves hill running and leg power.
Aerobic dance improves coordination and quickness. Avoid high-impact aerobic dance if prone to stress fractures. Cross country skiing is a terrific whole body and cardiovascular workout. Walking 40 minutes produces the same systemic benefits as 15 minutes of jogging. Speed and agility are improved through racquet sports.