With the opening of the Mount Hermon ski season, doctors at Safed's Ziv Hospital - which treats the injured - urged skiers to take precautions. Dr. Asa Lev-El, head of the hospital's Orthopedics Department, says that stretching and warm-ups are needed to increase the chances of going home without harm. Most of the skiers' physical complaints after a day on the slopes are muscle pains and spasms up to 24 hours later. These result from too much exertion by skiers whose muscles are not used to it. The body must be prepared for skiing, he said, and stretching and warm-ups must be carried out before putting on ski shoes. "One should never go out into the cold when your body is cold," he said. Exercises involving the thighs are most important, he added. Lev-El recommended that beginners wear longer skis, which slide slower than the shorter ones meant only for experienced skiers. After skiing, one should also exercise by walking, swimming short distances or using an exercise bike. This relaxes the muscles, he said. As for actual ski injuries, Lev-El said knees are the most frequent victims. If knees make a knocking or cracking noise and swell with a fall, go for immediate medical care. If this happens on the slopes, stop skiing and go immediately to a doctor of the condition can quickly become much more serious. People who already have knee problems should wear knee protectors and carry out proper exercise before skiing, he said. Shoulder dislocation, which usually results from a sudden braking or bumping into something, is also common among skiers and requires immediate medical care. This injury often requires long-term rehabilitation, including physiotherapy to restore normal motion of the limb, he said. Lev-El recommended that skiers wear thick, warm clothing that protects against the cold and serves as a bumper during falls.