Now that you get the concept, and you've built up some knee strength, start by working 15 minutes of Frank Fletcher's agility exercises into your routine once a week (or up to 45 minutes, three times a week, for advanced athletes). Mix them up: The variety will keep you on your toes. Do each exercise until you feel tired but not fatigued, stopping well before your form gets sloppy.
1. FAST FEET
Begin in a classic athletic "ready" position, standing on the balls of your feet with a slight bend in your knees. March in place, progressively shortening the height you lift your feet until they're barely rising from the floor. Swing your arms in time with your feet, as in a regular jog, and speed up the pace until you're beating out a staccato rhythm on the ground. Time: Beginners, start with 30 seconds; advanced athletes, three to five minutes.
2. PULSE SQUAT TO JUMP
You'll want to customize these fast squats based on the needs of your sport. For example, skiers and surfers should squat until the knees approach right angles; soccer players and trail runners, only to 45 degrees. Use the usual form for squats (back straight, butt out, knees behind your toes), but do them quickly, more like bounces than traditional repetitions. Do three to 15 quick pulses, depending on your fitness level, before explosively jumping straight up as high as possible and immediately returning to the pulse squats no rest. Beginners, start with ten sets before resting. Work up to 30 sets.
3. AGILITY LADDER
With an agility ladder ($90; performbetter.com) laid out before you on the ground, begin with simple "one-ins." Run along it with one foot outside the ladder, one foot stepping inside every other space. Then do it backwards. Comfortable with that? Try "two-ins" in every direction. Begin by placing your left foot in the ladder, then place the right foot next to it before moving the left foot one spot over. Repeat quickly. Ladder combinations are as endless as dance steps, but you can up the difficulty with high knees holding your hands out in front at hip height and touching your knee to your hand with each step.
4. HOPS AND JUMPS
On skis or on the basketball court, you're often forced to quickly jump off one or both legs in any direction. To train the body, you have to add that kind of variety to a jumping workout. Begin with both feet parallel and jump repeatedly in any given direction. As you progress and grow stronger, do the same on one foot, unless you have injuries. Next, try "two-ways" hopping in one direction before stopping and returning in the other. To boost your reaction time, have a friend quickly call out random directions, and try to keep up. Be sure to work your way up over time no hopping while you're sore.
5. DEPTH DROPS/JUMP-UPS
These two basic moves build explosiveness and can help you absorb big impacts from ski jumps and the ensuing crashes. Begin by standing on a solid platform about knee height off the ground. Step or hop off, allowing gravity to bring you down. Absorb the impact by dropping into a squat, trying to be "quiet" or "soft" with the feet, and stick the landing like a gymnast. Now turn around and do a standing jump off both legs back up to the platform. Repeat until tired.
6. DODGEBALL TENNIS
In this agility game, start by side-shuffling back and forth across a room or doing fast feet laterally. Your partner then takes a racket and a hopper of tennis balls and starts blasting them at your legs. The idea is to dodge them but continue your task. For your friend, this is almost as fun as driving golf balls at that dude in the cart.
7. REACTION BALL
To add some chaos to your training, buy one of those irregularly shaped balls that bounce in random patterns ($24; kwikgoal.com). On your own or with a partner, throw it on the ground or against a wall and try to catch it. This is like chasing the chicken, only it's PETA-approved.
8. BLINDFOLD DRILLS
You can add difficulty and increase your proprioception (a.k.a. body awareness) with most of these exercises by simply blindfolding yourself. "A huge part of the brain is used for visual perception, interpretation, and reaction, which is a slow process," says Fletcher. "But sports require us to make rapid decisions without executive interference from the brain." As your agility and strength improve, try the depth drops, single-leg hops, and fast-feet moves blindfolded. (Not recommended for dodgeball tennis.)