Many runners steer clear of anything that even remotely resembles a dumbbell, figuring that pumping iron will only bulk them up and slow them down. But in truth, strength training is exactly what runners need to do.

"With running, you tend to use the same muscles over and over again," says IDEA master trainer Lisa Garrity of Fitness Express in San Diego, CA. She explains that this repetitiveness can lead to three types of muscle imbalances.

One type is a strength imbalance between opposing muscle groups, such as the quadriceps and hamstrings, which can lead to muscle pulls and an assortment of knee ailments. A 3:2 strength ratio between quads and hams is ideal. You can test your ratio by doing a maximum lift on both a leg extension machine and a hamstring curl machine. So, for instance, if you can do a leg extension with 30 pounds, you should be able to leg curl 20 pounds.

Another type of muscle imbalance occurs between the lower-body muscles, which are heavily recruited when you run, and your middle- and upper-body muscles, which are primarily involved in stabilizing your body. When your middle and upper body are weak compared to your leg and hip muscles, you're more prone to low back pain and that poor, round-shouldered posture runners are unfortunately so famous for. You're likely to fatigue more easily, too, because when one muscle is spent, that's often it for the rest of the body -- you're only as strong as your weakest link.

Running can also cause imbalances of strength and flexibility, either between muscles or within the same muscle. If, for instance, your hip flexors are strong but tight, this can lead to hip or back pain.

If your quads are strong and your hamstrings are tight, this will impede proper running mechanics and contribute to all sorts of knee issues.

The good news is that one of the best places to correct muscle imbalances is in the weight room. Garrity has designed a strength program especially for runners, combining basic strength-training exercises with some unusual running-specific moves.

She recommends performing this workout two or three times a week, shooting for 12 to 15 reps. When an exercise works each side separately, do 12 to 15 reps to each side to complete one set. Do two or three sets of each exercise, resting 30 to 60 seconds between each set. You can also add squats, lunges and leg curls to this routine, since they're also runner friendly. For maximum benefit, do the routine every other day, preferably on days when you don't run.

Stick Lunges
Runner Essentials: Besides providing strength and power to the lower-body muscles, this exercise helps you gauge upright posture while moving. It trains the hip abductors and adductors to stabilize the knee, as well. Set-Up: Grab a very lightweight bar or broomstick. Stand tall with your feet hip-width apart. Hold the broomstick behind your back lengthwise along your spine, the top hand with thumb down, elbow bent and pointed toward ceiling, and the bottom hand with thumb up and against your lower back. The stick should gently touch the back of your head, the center of your back and your tailbone.	Move: Using the broomstick to help keep your upper body still and aligned, step your left foot forward about a stride's length and bend both of your knees, left knee aligned with left ankle, until your left thigh is parallel to the floor and your right thigh is perpendicular to it, heel lifted. Don't let your knees travel in front of your toes. Stand back up to the start, again using the stick to help stabilize your upper body. Continue alternating left and right to complete all reps.
Bench Stand-ups
Runner Essentials: This move develops strong and balanced glutes and hamstrings to help propel the body forward during running and to take some of the heat off the quads. It also uses the hip abductors and adductors to keep your body stable, which improves knee tracking and control, an important issue for runners. Set-Up: Hold a dumbbell in each hand and stand tall on top of the lengthwise center of a knee-high step or flat bench. Face the front of the bench with your left leg straight so that your left foot hangs a few inches off the bench. Relax your arms down at your sides, palms facing in, and pull your abs inward.	Move: Keeping your posture tall and your hips and shoulders square to the front, bend your right knee slightly so that your left leg lowers toward the floor a few inches. Straighten your right leg and stand back up to the start. Move through reps quickly but with control, keeping your right knee aligned with your second toe. Complete all reps, repeat with the right leg, and continue alternating legs to complete all sets.
Bent-knee calf raises
Runner Essentials: This dynamic move enhances ankle and calf flexibility and increases the strength of the deeper calf muscle, the soleus. It can also help stave off lower leg fatigue in the later stages of a run. Set-Up: Place a step bench against a wall with two to three sets of risers underneath. Stand tall on top of the step facing the wall with just the balls of your feet on the step so your heels hang off the edge. Place one or both hands against the wall for support. Pull your abs inward.	Move: Lower your left heel as far down as is comfortable as you bend your right knee slightly and lift up your right heel. Alternate heel positions at a quick yet controlled speed and continuously move through reps until you complete an equal number of reps with both legs.
Toe Pull
Runner Essentials: Strong shins prevent shin splints and counterbalance strong calves to keep these opposing muscle groups in balance. Set-Up: Tie an exercise band or tube into a circle and anchor one end to the bottom of a door or sturdy object. Sit up tall on the floor facing the door with your left knee bent, foot flat on the floor, and right leg out in front. Wrap the free end of the band around the top of your right foot just behind your toes, and place your palms on the floor for support.	Move: Flex your right foot to move your toes toward you as far as you comfortably can. Hold the top of the movement for a moment and return to the start. Complete all reps and repeat with the left foot. Continue to alternate left and right to complete sets.
Back Extension
Runner Essentials: This strengthens your lower back to help absorb pounding and, by balancing out lower back strength in relation to abdominal strength, promotes good posture even when you're fatigued. It also helps open your hips so you can lengthen your stride. Set-Up: Lie facedown with your hands in front of shoulders, palms pressed into the floor. With the underside of your toes anchored into the floor and heels up, "zip" your legs firmly together. Pull your abs in.	Move: Without using your hands to push off, arch your back to lift your chest as far off the floor as you comfortably can. Your hands will lift up with you, but keep your toes anchored, your abs pulled inward and your legs zipped. Hold a moment at the top and slowly lower to the start.
Alternate Hand Swings
Runner Essentials: This move teaches core stability while your arms are in motion. It promotes balanced strength between your abs and lower back muscles, which helps prevent low back fatigue and can help improve your end-of-run kick. Set-Up: Sit on the floor, knees bent and feet flat on the floor. Keeping your spine long and straight, lean back to a 45-degree angle. Using your ab strength to maintain your positioning, lift both feet about 2 inches off the floor, then extend your left arm over your head and your right arm down along your side.	Move: Maintaining a strong and still position with your body, switch arm positions so that your right arm is up over your head and your left arm is down along your side. Move continuously until you complete all reps. Do an equal number of reps on both sides.
Dynamic Biceps Curls
Runner Essentials: A strong and steady arm swing will balance upper and lower body usage when you run. It'll help propel you forward more efficiently. Set-Up: Hold a very light dumbbell in each hand and stand tall, feet hip-width apart, knees slightly bent. With your palms facing in, bend your elbows so your lower arms are parallel to the floor and close to your sides. Keeping elbows bent, drive your left elbow back until your left hand is just in front of your waist and lift your right arm until your hand is level with your forehead.	Move: Slowly "swing" your arms until your left hand is up and your right hand is back. Move continuously until you complete all reps.
One-arm Kneeling Rear Flye
Runner Essentials: This exercise targets the rhomboid muscles between your shoulder blades and the rear delts to stabilize your upper back. Set-Up: Holding a dumbbell in your left hand, straddle your legs a stride's length apart, right leg in front, and bend both knees until your left knee touches the floor and your right thigh is parallel to it. If you need extra cushioning, place a rolled-up mat or towel under your left knee. Lean forward from your hips and rest your right arm on your thigh for support. Straighten your left arm down near the inside of your right leg, palm facing in.	Move: Lift your left arm up and out to the side until it's at shoulder height and your palm faces the floor. Slowly lower to the start. Complete all reps and then repeat with your right arm. Continue to alternate left and right to complete sets.