Walking and running are great ways to build leg strength. However, over time, your legs become accustomed to the motion and eventually can hit a plateau. This could also limit your performance. Here are some tips to increase your leg strength, which could lead to longer and more productive sessions.

Change it up — If you find yourself constantly running or walking at the same track or trail, find a new place and give it a try. Go to a place with hills, since they are a great way to build leg strength and add some extra intensity to your session.

Cross Training — Cross training is an excellent way not only to enhance your walk or run, but your overall fitness as well. Combining running and walking with strength training and other forms of aerobic exercise like swimming, elliptical training and cycling can add variety to your workout and can greatly improve your performance. Sports like soccer and basketball are great for improving leg power as well.

Resistance Training — Resistance training with free weights or weight machines is a great way to improve leg strength and add an extra kick to the latter stages of your run and walk. Some good leg strengthening exercises include:

1. Squats — Squatting is one of the best resistance workouts you can do. This exercise works almost all of the muscles in the lower body and is a great way to build leg strength. This is a must-have in your program if you decide to begin resistance training. While squatting, be sure to keep you feet flat and push up through your heels. Keep your back flat and your torso upright and look straight ahead.  
2. Lunges — Lunges are a great way to enhance strength and stability in your legs since you are forced to balance all of your body weight on one leg for a short period of time. Be sure not to let your knee come over your toes while lunging and keep your torso erect while looking ahead.  
3. Leg Curls — This exercise works the back part of the legs, the hamstring muscle group. This is especially pertinent for runners since most runners have very strong quadricep muscles (the ones on the front part of the leg) and have weak hamstring muscles. Curl your legs as far up as they can go, and slowly let the weight back down, but don't let the weight stack touch and lose all the resistance. Strengthening the hamstrings will restore a balance to the leg musculature and aide in preventing running injuries.