Downhill skiing, for many, is the ultimate recreation. But whooshing through the powder demands a lot of your body. Getting in shape before you go and using common sense once you're there can help you leave the slopes with great memories — instead of debilitating injuries.

Edward Laskowski, M.D., a physical medicine and rehabilitation specialist and co-director of the Sports Medicine Center at Mayo Clinic, Rochester, Minn., was a member of the Team 2002 medical staff at the Olympic Polyclinic during the 2002 Winter Olympics and is a former member of the Professional Ski Instructors of America. He notes that the forces you encounter on skis can be extremely hard on your ligaments.

In hockey, for instance, a two-foot quick stop exposes a player's lower extremities to about 15Gs — where one G equals the force of gravity. For a downhill skier making an instantaneous stop or catching an edge, the force can be as high as 139Gs. That's a lot of force to place on your joints and ligaments, especially your knees.

You can take measures to work with these forces and avoid injury. Just plan ahead and take pre-conditioning seriously.

Today's rigid plastic ski boots allow for better control of your skis than the old leather ones, which has reduced the number of ankle and lower leg fractures. However, modern boots transfer much of the force and torque of the ski to your knee.

One of the most dreaded skiing injuries is a rupture of the anterior cruciate ligament (ACL). The ACL is one of four ligaments that attach your upper leg bone (femur) to your lower leg bone (tibia). The ligaments also prevent your lower leg bone from extending too far forward. An ACL-injured knee may feel unstable at times and may even buckle, especially during jumping or other high-impact activities, as well as during sports that require rapid cutting or pivoting, such as tennis or basketball. An ACL injury may make the cartilage in your knee joint more susceptible to damage.

Advanced skiers are especially at risk of an ACL rupture when they land from a jump or try to recover from a fall.

"As they go back on the tail of the ski and try to recover, the quadriceps — the muscles on the front of the thighs — contract vigorously, and the rigid boot and ski tail push the lower leg bone forward, which can rupture the ligament," Dr. Laskowski says.

Beginning skiers are at risk of ACL injury when an awkward fall flexes their knee at the same time that the rigid boot pushes their lower leg forward. Newer ski bindings, which release at more angles than older bindings, may give some protection against ACL injuries, but they aren't the entire solution.

"A good conditioning program to prepare the muscles of the lower leg for the job of skiing is one of the best things you can do to maximize your protection from injury," Dr. Laskowski says. "Taking lessons from a qualified instructor is another. Most of the things you can do while skiing to maximize your injury protection are just examples of good ski technique."

Your hamstrings — the muscles on the back of your thighs — also help prevent your lower leg from extending too far forward. Many people neglect their hamstrings in favor of the quadriceps. But hamstring-strengthening exercises, including the hamstring curl, help stabilize the knee and provide for more balanced knee strength.

SLIDE SHOW

Get in shape before you hit the slopes

Experienced skiers may be able to prevent ACL injuries by resisting the temptation to fight a fall to the bitter, sprawled-out end. "Once you're going down to where your hips are below your knees, go with the fall," Dr. Laskowski advises. During a fall, you can minimize your risk of an ACL injury if you can keep your arms forward, skis together, hands over your skis and hips above your knees.

Ski-related injuries to the arms, hands and fingers tend to involve damage to the ligament in the webbed space between your thumb and index finger. As you fall, the ski pole can stress your hand. Wrapping your hands into ski pole straps puts you at greater risk of this injury. Pole handles with molded contours also can lock your fingers and thumb in a stressed position when you hit the snow.

To prevent skier's thumb, avoid wrapping your ski pole straps around your hands. Let go of your ski poles before you fall so that your hands land flat on the ground rather than in an awkward position. You can also purchase ski gloves with rigid reinforcement in the thumb area to help protect the ligament in a fall.

Here are some suggestions to help you enjoy downhill skiing and stay safe.

• Take a lesson. Learn the basics — how to stop, turn and control yourself — from a qualified instructor. Don't be tempted by others to ski on runs that are more difficult than you can handle. Progress to more difficult runs only when you're able to establish that you can ski in control and can stop yourself whenever the situation demands it.

• Tune your bindings. Surveys show that perhaps half of all skiers use improperly tuned bindings. The tension of the binding determines when your ski releases from the boot. When you fall, the timing of the binding release can make the difference between a harmless tumble and a major wipeout. Get your skis, boots and bindings checked by a certified ski technician every year at a ski shop that follows American Society for Testing and Materials standard practices.

• Wear a helmet. If you're just beginning or you're an aggressive skier, consider wearing a helmet to help prevent head injury. Your kids should always wear a helmet.

• Show respect. Most deaths on the slopes result from skiers who run into objects or other skiers, so ski responsibly. Skiers can peacefully coexist with snowboarders on the slopes, but be alert and realize that a snowboarder's turning arc will usually be much wider than a skier's.

• Stay away from alcohol. Alcohol-impaired skiers, like drunk drivers, put themselves and others at risk of serious injury or death.

• Stay hydrated. Drinking plenty of water is as important in winter as it is in summer, especially when you're exerting yourself in dry, high-altitude conditions. "Always drink before you are thirsty," Dr. Laskowski says. "When you get thirsty, you may already be as much as one-third down on your water storage."

• Dress in layers. Wear insulating layers to protect yourself from the cold. Protect your eyes with sunglasses or goggles, and use sunblock on exposed skin.

• Don't overdo it. Injuries on the slopes tend to occur at the end of the day, the time when the energy stores in your muscles can be at their lowest. Consume plenty of carbohydrates before you ski and throughout the day to ward off muscle fatigue. But the best advice is to end your day of skiing before you get too tired to ski safely.

• Drive safely. Some ski trip accidents happen in the car, not on the slopes. Check ahead for road conditions and be prepared to use tire chains in hazardous conditions.

• Consider health conditions. Ask your doctor what precautions to take if you'll be skiing at high altitudes and have lung disease, heart disease or asthma. Make sure your boots aren't too tight if you have diabetes or decreased sensation in your feet due to heart disease or nerve damage. And remember — if your feet start to feel numb, it's time to go to the chalet or clubhouse to rest and warm up.

A vacation at the ski slopes is meant to be fun. To make the most of your time away with family or friends, prepare for the slopes with a program of physical training. And before you go, have a certified technician adjust, maintain and test your boots and bindings.