A study in a 2009 issue of the "Journal of Strength and Conditioning Research" concluded that core strength exercises, which primarily target the abdominal and back muscles, can be effective in increasing runners' performance. Use a stability ball to perform crunches by placing your low back on it with your feet firmly planted on the floor. With your hands behind your head, crunch up and down. Turn over and place your ribs on the ball with your legs extended behind you, balanced on your toes, to train your low spine. Extend your arms alongside your trunk and lift your chest off the ball until you feel a slight pull in your back muscles. Plank holds and bird dogs, in which you alternate reaching opposite limbs from an all-fours position, round out a runner's core workout. Perform all of the moves for at least one set of 10 to 20 repetitions.
The hamstring muscles at the back of your legs provide power for the push-off phase of each stride, while the quadriceps catch you as you run down hills. Train both these muscles together with a single-leg squat. Stand on your right leg and bend your left leg behind you. Flex your right hip and knee until your leg is bent about 50 degrees, and then return to a straight up-and-down position. Do all the reps on the right and then repeat on the left side. You can hold dumbbells in each hand to increase the challenge. To further target the hamstrings, perform leg curls on a weight machine in which you hook your ankles under a pad while lying face down and bend your legs to bring your heels toward your buttocks. Hamstring pushups off a stability ball are another powerful move for a runner. Prop the ball against a wall and lie on your back with one heel on it; the other leg is extended to the ceiling. Lift your buttocks up and down in a slow, controlled manner and then change legs. Do all of these moves for up to three sets of eight to 12 repetitions.
When you run, your calves lift the heel approximately 1,500 times per mile, reports "Runner's World." Strong calves give you power and prevent the ankles and feet from bearing the brunt of your running impact. Calf raises are a simple way to strengthen the gastrocnemius muscle -- the large triangular-shaped muscle at the back of the lower leg. Stand on a step or short box at the gym with one heel hanging off. Slowly lift and lower the heel to activate the calf; repeat on the other side. Seated calf raises, which you can do while sitting at the edge of a bench with your heels hanging off a raised platform and a barbell resting across your thighs, train the smaller soleus muscle of the calf, which is also important to healthy lower leg function.
Weak hips can be the reason you are suffering from all sorts of injuries in the lower portion of your legs, including knee strain, Achilles tendititis and illiotibial band pain. Use a resistance band to train the outer hips. Loop the band around a stable object and your right ankle. Stand with your left side facing the anchor point of the band and draw your right leg out to the side; pause and then slowly return to start. Do one to three sets of 10 repetitions for each leg. A hip raise off a stability ball targets your hips and your glutes, which provide power for your stride. Lie on your back and, with legs extended, prop both feet up on a stability ball. Slowly lift your hips up off the floor to create a bridge; your body should form a diagonal line from your head to your toes. Aim for two sets of 12 repetitions.