Isotonic Training

Isotonic muscular contractions have a concentric phase, in which you lift the weight and the muscle shortens, and an eccentric phase, in which you slowly lower the weight and the muscle lengthens under tension. Isotonics involve a constant external resistance, like gravity, barbells, or dumbbells. Although the resistance is always the same, the force to move that resistance varies with the joint angle as the weight is lifted and lowered. Depending on the exercise, an isotonic movement can require more force to lift the weight at the end of the movement (squat), the beginning of the movement (dead lift), or the middle of the movement (biceps curl). The lifter also controls the speed of the movement. These components of isotonic exercise mimic our movements in life and sports, so doing isotonic exercises can be very functional. The majority of exercises in this book are isotonic for several reasons: they simulate life and sports activities, they are easy to do, and they don't require special equipment or a gym membership.

The exercises in this book focus on free weights because of all of the advantages they have over machines. With free weights, the possibilities are endless. You can use gravity, barbells, dumbbells, medicine balls, and even trucks. Stretch cords and tubing have value as training adjuncts for travel (because of their portability) and in rehab, but they are not very useful for strength training. Tubing can't put the same amount of loading on the muscle and bone as free weights. This book describes some exercises that use a stability ball as an accessory, as part of a good strength-training program. As an alternative to performing the strength-training exercises on stationary benches, using stability balls is a fun way to incorporate balance and function.