You're logging your time in the pool, on your bike, and on the trails when your worst nightmare emerges-an injury puts you on the sideline.

Overuse accounts for upwards of 80 percent of all injuries according to a University of Western Sydney study of more than 100 competitive triathletes. You're more likely to hurt yourself running and less likely to get hurt swimming.

Fortunately, what's great about triathlons is if you can't run or can't bike, at least you can improve on the other two-thirds of the event, says Ian Murray, USA Triathlon certified coach and the host of the Triathlon TrainingSeries DVD.

Still, you don't want to become injured in the first place-and if you're proactive that won't be the case. Here are the five most common triathlon injuries and how to treat and prevent them.

1. Rotator Cuff Tendonitis/Shoulder Pain

The symptoms: Everything from a dull ache to a sharp pain in your shoulder. You'll especially notice it when your arm is extended above your head or during a freestyle swim stroke.

Why it happens: "The freestyle stroke develops the front of the shoulder and the chest muscles, creating an imbalance with the rest of the shoulder muscles," says Murray. Be particularly careful about ramping up a bunch of yards in the pool if you don't come from a swimming background and haven't perfected the right form yet.

How to solve it: Murray suggests stopping when the pain is at a whisper, and don't wait until it's a scream. Then rest, massage, and ice the affected area to reduce swelling.

Avoid it completely: Build up your shoulder strength by incorporating sets of lateral raises with light dumbbells or resistance bands (check out the correct form in the Men's Health Workout Center). This engages the rear deltoids and brings balance back into the shoulder.

2. Iliotibial (IT) Band Syndrome

The symptoms: A sharp pain or tightness on the outside of the knee just below the joint. The IT band is a key stabilizer for the leg, so when it flares up it's enough to debilitate runners or bikers completely.

Why it happens: The IT band starts in the muscles of the gluteus and hip and moves down the outside of your thigh. You can aggravate the IT band by upping your mileage too quickly. This happens as the knee is repetitively bent and straightened, causing greater friction between the IT band and the femur, leading to a flaring at the knee, says Mark Klion, M.D., orthopedic surgeon at Mount Sinai Hospital in New York City and 10-time Ironman competitor.

How to solve it: Spend time on a foam roller. The rolling breaks down knots and prepares muscles for stretching. Try this: Lie on your side with the roller starting at your inside hip. Rest your other leg's foot on the floor. Roll along your outer thigh from your hip to your knee.

Avoid it: If you have weak hips, that could be the main issue. Perform exercises to strengthen hip abduction like the StandingResistance-Band Hip Abduction from the Men's Health Workout Center. Or you can do more running-specific moves like walking lunges, says Troy Jacobson, head triathlon coach for Life Time Fitness.

3. Achilles Tendonitis

The symptoms: A pain below your calf and above your heel. You may also see a bump of swelling in the normally smooth Achilles tendon, or feel creaking or see redness in the tendon. The pain may not be very bad at first, but don't ignore it-it can quickly morph into a chronic issue if you don't deal with it.

Why it happens: The Achilles connects the large calf muscles to the heel. "When the calf muscles get tight, they pull on tendons below and cause micro-tears in the Achilles," says Murray. The tendon can also become inflamed with overuse or factors like overpronation when running.

How to solve it: Sit at your desk and roll the bottom of your foot with a golf ball or lacrosse ball. If the pain goes away as you run, feel free to run on it. But if pain starts at the beginning of your run and gets worse, consider taking a break from running, says Klion. To help it heal, apply cold therapy to the area that hurts for 10 to 15 minutes every two to three hours.

Avoid it: Strengthen stabilizing muscles in the lower leg by balancing on a thick foam mat or a BOSU ball. Also, stretch both calf muscles before and after runs with static stretches that target the Achilles and calf.

4. Patellar Tendonitis

The symptoms: Pain in the center of your knee, almost right under the kneecap. You'll especially feel it when seated for long periods of time-like biking-or when walking up and down steps.

Why it happens: The quadriceps muscle in the front of your thigh becomes tight or inflamed and pulls the kneecap against the joint. The culprit: in triathletes, usually an improper bike fit.

How to solve it: First, schedule a professional bike fitting. That usually will fix the problem. To speed healing, roll out your quadriceps on a foam roller.

Avoid it: Strengthen your quads, says Jacobson. A dumbbell split squat targets your quads and every other muscle in your lower body, including your glutes, hamstrings, and calves. Also, avoid doubling up hilly weeks of riding with hilly weeks of running, since both punish on your quads-alternating is safer.

5. Stress Fractures

The symptoms: Stress fractures in triathletes occur mainly in the hip, foot, or tibia (the main bone in your calf). You'll feel pain in the bone during exercise, and probably see some swelling.

Why it happens: When you dramatically increase in training volume without proper adaptation and recovery, the constant pounding can fracture the bone. (Regular rest gives it time to repair, avoiding injury.)

How to solve it: If you suspect a stress fracture, stop running completely and seek out an X-ray from a sports doctor. Often you'll have to rest for 6 to 8 weeks to let the stress fracture heal. The upside: More time to perfect your swim form!

Avoid it: Start by being smart with your mileage when running-especially if you're relatively new to the sport-and take rest days throughout training. "I say do 30 to 40 percent of training on a treadmill or surface other than asphalt to take the pounding off your legs," says Jacobson.