Stand up with feet shoulder-width apart. Bend knees as if you are going into a squat and jump forward. Get down as low as possible before jumping. This is best done on a track. One "hop" counts as one repetition. Try to go at least 25 meters per circuit.
Standing with feet shoulder-width apart, bend knees to be lower than a "sitting" position, with thighs almost parallel to the ground. Be sure not to let the knees go over the toes. Bend in the legs, not the back or buttocks. Going down and back up counts as one repetition. Try to do 30 repetitions per circuit.
For more advanced runners, this can be done holding dumbbells. Using a low weight bench, place one foot on the bench, keeping the other foot on the ground. Raise yourself up to stand on top of the bench, then use the same foot to push off and place the other foot back onto the ground. One up and one down is one repetition. Start with 20 repetitions on each leg per circuit.
Sit-ups increase core strength, important for efficient running and endurance. Lie on your back, with feet on the ground, knees bent. Cross arms over chest or place behind head. Use your abdominals to sit up to knees. Do not use arms or hands to pull the body and push the head forward. Keep feet planted on the ground. If this is difficult, have a friend hold your feet or place them under a couch to keep them in place while doing the repetitions. Up to the knees and back down to the floor is one repetition. Try to do at least 30-50 repetitions per circuit.