The crosstraining report: get on the ball.

In April we discussed plyometric exercises to help develop your lower-body strength, explosiveness, and speed. These skipping, bounding, jumping, and hopping routines are performed vertically and are very sport-specific to running. But the body's core--consisting of the lower and upper back, torso, oblique, and abdominal muscles--is also used in running and necessary to keep strong. To ensure that you don't neglect the core, try the following medicine ball exercises. The medicine ball is enjoying enormous popularity these days thanks to celebrity fitness trainers like Gunnar Peterson promoting its many benefits. Don't let this stop you: the ball works.

Medicine ball exercises emphasize movements, not individual muscles. The whole body is involved, which is often more beneficial than narrowly-targeted exercises. Before you begin, then, it's especially important to remember good form: your back should be straight and your knees bent, especially when picking the ball up from the floor. When you throw backward, do not position the ball too far behind your head. Start with a light ball and proceed to a heavier one in later weeks. Avoid catching the ball directly in front of your face.

For strength and endurance, perform two to three sets of six to 12 repetitions. Use a heavier ball for more strength, and a lighter ball for endurance, balance, and flexibility. To focus exclusively on endurance, perform six sets but with 12 to 24 repetitions. It takes only about 15 minutes to complete a session of six or more exercises. The ball should be heavy enough to slow down your movement, but light enough to allow for accuracy and range of motion. It's a good idea to err on the lighter side than heavier. A beginner might try a 6-lb ball, whereas 10 lbs is a good intermediate ball, and 12 lbs for an advanced sized ball. Men can usually start with the 10-lb ball; women might begin with the 6-lb size. Most of these exercises can be performed alone.

Chest pass. Starting with the ball at mid-chest, throw the ball toward a solid wall. Stand far enough away for the ball to bounce once before returning to you. Catch it on the rebound and throw it back to the wall immediately. You may also omit the bounce to the floor.

Side swing. Stand sideways to a solid wall about 6 or 7 feet away. With your right foot closest to the wall and feet shoulder-width apart, rotate at the waist clockwise (toward the wall) and throw the ball at the wall. Do not move your feet; keep them firmly planted. Catch the ball on the rebound while moving in a counterclockwise direction (away from the wall). Without losing momentum, throw the ball back and repeat. You may choose to let the ball bounce or not; adjust your distance to the wall accordingly. Next position your body with the left foot closest to the wall and do the same number of repetitions.

Underhand throw. Start in a full squat position with the ball between your legs and raise straight up, throwing the ball for height. Catch and repeat.

Overhead throw. Start with the ball behind your head, feet shoulder-width apart. Taking one step forward, launch the ball forward over your head toward a wall. Try to throw hard while retaining good form.

Backward throw. At half-squat with the ball between your legs, stand up into a slightly-bent knee position and throw the ball backward behind your head. This exercise is easier with a partner to catch it.

Abdominals (with partner). Lie on the floor with knees bent, facing your partner standing above you. As your partner drops the ball toward your chest, catch the ball (eccentric contraction) and immediately throw it back (concentric contraction). Repeat 24 times, for two sets.

Medicine ball workouts are a subset of plyometrics, applying the same principles of rapid concentric and eccentric muscle contractions. Perform these exercises on a day reserved for crosstraining, or after your warm-up when you are still fresh. The stress involved means it is not a good idea to do them when your muscles are already fatigued, as after a speed workout.

There are a variety of free-weight exercises you can do sitting on the ball for added benefit. For example, simple bicep curls work more than just your arms and burn more calories by requiring you to balance on the ball in a sitting position. This strengthens your core at the same time. These exercises are typically performed on much larger medicine balls not designed for throwing. Some of these balls may weigh up to 30 lbs. Most of the exercises outlined here are for balls a third or so larger than a basketball, and better designed for throwing and catching.

(The Complete Guide to Running: How to be a Champion from 9 to 90 by Earl Fee, 2005, Oxford: Meyer & Meyer Sport, UK, pp. 361-364)