Overuse syndrome plague triathletes, who often push their bodies to the limit.

On the misty shore, they're poised for action. The starter's piston fires, and throngs of triathletes run to the water's edge and begin the first leg of the race. With each stroke, they cut through the water toward the next challenge-the bike race. As they fly down city streets and country roads for miles, they chant the mantra "Pace yourself. Pace yourself. You still have to run."

Nearing the start of the foot race, they toss bike helmets aside. Legs pump, chest heaving, they run, sometimes for more than 20 miles. Crossing the finish line, they finally stop, exhausted, yet exhilarated..

The ultimate test of speed and endurance, the triathlon combines swimming, cycling and running in a single event. In the United States, 300,000 active triathletes participate in competition, according to the USA Triathlon Federation. This number is expected to rise with the triathlon's introduction to the 2000 Summer Games in Sydney.

Triathlons are broken into three categories, each with varying distances per event. Swimming is the first event, followed by a lengthy bicycle segment and finishing with a run.

Despite the arduous nature of the event, most athletes aren't injured in competition. In fact, most injuries occur from overtraining. It's not surprising. To prepare for each discipline, athletes train for speed, endurance and racing strategies. Training programs and sessions vary, with some sessions lasting only 30 minutes, two to three times a week, to workouts lasting five or six hours, seven days a week. Over time, these training sessions wear and tear the body.

Eighty-three percent of triathletes surveyed by Cipriani et al. were injured during training; 49 percent of the respondents in another study sustained injuries that forced them to stop training.

Training for three events makes triathletes more susceptible to certain injuries. For instance, the Achilles tendon may be more susceptible to tendinitis when swimming and cycling are added to a training program. And an untreated dysfunction in one part of the body can lead to problems elsewhere. For example, a knee injury can cause extra stress on the low back, resulting in low back pain. The cumulative effects of cycling and swimming also can contribute to tight, fatigued calf muscles, which make the legs more prone to injury during a run.

In general, the back and lower extremities are commonly injured in triathletes, with the most frequent injuries occurring to the hamstrings, knees, lower leg and ankles. In one study of intermediate-level triathletes, the lower leg, knee, foot, ankle and Achilles areas accounted for 61 percent of documented injuries.

The following is a run-down of the most common injuries by sport and ways you can treat them:

• Swimming: The first event n a triathlon, the swim takes place in open water where athletes take the plunge in mass groups. Adding to the challenge of an endurance swim is a crowded swimming space filled with flailing arms and legs. Although there's risk of collision injuries, swimming has the lowest rate of triathlete injury and the fastest rate of recovery. Shoulder pain is the most frequent complaint, which causes temporary interruptions in training and competition for 66 percent of all elite swimmers.

For athletes with shoulder overuse injuries, treatment includes a combination of rest, ice, anti-inflammatory medication and physical therapy to improve body mechanics. Teach your patient modified stroke techniques and proper stretching exercises; poor stretching can lead to undue tissue stress during cycling and running.

While shoulders can take a beating in the swimming portion of the competition, so can legs. In freestyle swimming, repeated ankle plantar flexion occurs during the standard flutter kick. This kicking technique promotes a shortening of the Achilles tendon and gastroc-soleus muscle group, which can cause increased stress during cycling or running.

Triathletes aren't usually experienced swimmers - only 20 percent have a swimming background - so training should focus on ways to conserve energy during the swim segment of competition. Emphasize proper stroke technique, upper extremity strength and endurance in the water.

• Cycling: On the bike course, triathletes race along city streets and rural roads, traveling at speeds between 18 to 25 mph. Most cycling injuries are trauma-related; the head, face, arms and legs are the most frequently injured. Sixty-two percent of all serious cycling injuries involve head trauma, driving home the importance of helmet use. Helmets reduce the likelihood of serious skull fractures by about 85 percent and cut the incidence of facial injuries by more than 73 percent.

In addition to traumatic injuries, cyclists frequently experience neck, back and knee pain from overuse. Other non-traumatic injuries include ulnar neuropathy, iliotibial band friction syndrome, anterior knee pain and Achilles tendinitis. An ulnar neuropathy occurs when pressure is exerted through the arm to the heel of the hand that's supporting the upper body on the handlebars. Without frequent changes in hand the arm position, the ulnar nerve compresses at the wrist or heel of the hand, causing weakness to the fourth and fifth digits and eventually leading to ulnar nerve damage. Iliotibial band friction syndrome occurs when a tight iliotibial band rubs on the lateral knee joint structures as the knee flexes and extends during pedaling.

Only 10 percent of triathletes have a background in cycling, so these athletes may not be aware of proper body positioning on the bike, which can prevent many of these injuries.

To properly treat cycling injuries, review the patient's training program and his position on the bike. Correct faulty pedaling techniques and address workout/training routines that may exacerbate the injury. For greater mobility of the lumbar spine, hips and knees during cycling, increase flexibility with stretching exercises.

Discourage your patients from using larger gears for faster speed because it places greater stress on the patellafemoral joint and quadriceps - both of which are important to cycling and running. Larger gears increase joint compression loads on the patellar femoral joint, whereas smaller gears allow an athlete to ride with a higher cadence, therefore causing less joint compression loads.