Sport-Specific Training: Improve performance and decrease risk of injury by prepping your knees for mogul fields, marathons, and other targeted activities. Wendy McClure, personal trainer and co-owner of Body Dynamics in Boulder, Colorado, advises pro clients to incorporate these exercises into workouts three times per week, starting two months prior to the season. To increase difficulty, hold weights for more resistance and place a pillow underfoot to create instability.

Cycling > Split Squats
Stand with one foot forward, one back, a few feet between them and your hips square. Lower until your back knee almost touches the floor, then rise. Continue 30 seconds, then switch stance and repeat.

Skiing > Sideways Squats
Stand sideways a few feet from a wall and lean toward the wall, bracing yourself with your hand. Your unweighted inside leg is bent. Lower into a squat on the outside leg, then rise. Do two 30-second sets. Switch sides and repeat.

Hiking > Partial Step-Throughs
On a narrow step deck or platform, step up on your right leg, and bring the left up and through as if you're going to step down to the other side, but dip down only about 15 degrees, then move back to the start position. You should be balanced on the same leg throughout the movement. Repeat for 30 seconds on each leg.

Running > Paper-Plate Half Circles
Set a paper plate on the floor one stride length behind you. Balance on your left leg while extending your right foot back so your toes are lightly resting on the plate. Sink into a semi-squat position on your left leg. Now trace a full half circle with your right leg (don't let your knee dip inward), sliding the plate along the floor until it's in front of you. Slide plate straight back. Repeat 30 seconds on each leg.

Negatives and Plyometrics: Conventional weight-lifting programs strengthen muscles as they contract. Problem is, real-world sports often demand that your muscles lengthen under load. It's called an eccentric action, and it's what happens when you control your descent while hiking, running, or skiing. Work this braking action with negatives and plyos, which rely on resistance rather than lifting. For the following exercises, focus on excellent form and slow, natural rhythm.

Drop Jumps
On a box, step, or platform (start small), step up and drop to the floor, lowering into a squat, then spring straight up. Four sets of six to ten. Advanced: Hold a medicine ball over your head.

Front Squats
Hold an unweighted squat bar at the top of your chest. Lower into a squat on a ten-count pace, then explode up. Three sets of four to six. Advanced: Add 10 to 20 pounds.

Single-Leg Hops
On a level stretch of grass or track, leap forward from one foot to the other for approximately 20 yards. With each landing, hold yourself still, balanced on one leg, for five seconds. Do four sets. Advanced: Jump at a slight angle, alternating sides, and touch the ground with your outside hand on each landing.

Downhill Repeats
Fill a pack with weight (start light and increase gradually). On a sloping trail, hillside, or stadium steps, hike to the top and descend in small bounds. Keep your knees bent slightly, so they absorb impact like shocks during the descent. Do four to six reps of 50 yards. Advanced: Add weight and do reps of 100 yards.

MIX AND MATCH
You know cross-training is smart, but do you know how to choose a complementary combination of high- and low-impact activities? Use this guide to get the most out of multisport.

Sport: Running
Complement: Swimming with fins
Payoff: Adds low-impact balance to your routine. Fins help isolate quads and hamstrings to build leg strength.

Sport: Skiing
Complement: In-line skating
Payoff: Lateral movement mimics skiing motion, so you build hip strength and muscle endurance.

Sport: Cycling
Complement: Running
Payoff: The higher-impact activity helps promote bone density, build leg strength, and keep your weight down.

Sport: Mountain climbing & hiking
Complement: Mountain biking
Payoff: Pedaling up steep, technical trails develops leg and core strength. And descending? Well, some things are just for fun.