Dear David and Trish:

First, I want to let you know how much I enjoy your column. I look forward to it every Sunday. And, here’s a question for you:

Growing up in the 50’s, I recall a big "movement" towards what was called "Isometric Exercises". I even remember these being taught in school. However, it seems to have faded away (like some of my muscles!). Can you tell me what happened?

Sincerely,

Brad in Edgewater

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Dear Brad,

Unfortunately, that study wasn’t accurate. Although it has been shown that strength gains are possible from isometric contraction these strength gains are minimal, and are only at the specific angle at which the exercise is performed. This, of course, poses a real problem (we’ll address that later).

In spite of it’s limitations, isometric exercise has NOT disappeared (Trish and I use it often for our Home Training clients). However, it is used for specific purposes, NOT as a substitute for Isotonic or Isokinetic exercises. OK, got you with those big words again! Let’s define…

Isometric: Exercises in which a force is applied to a resistant object. An example is pushing against a brick wall. Although there is a build up of tension in the muscles there is no actual movement. To increase strength it is necessary to maintain a position in any one exercise for between 6 to 10 seconds. The exercise should then be repeated 5 to 10 times, each time ensuring maximum muscular contraction. By the way, Isometric exercises are extremely good for strengthening muscle groups around an injured joint

Important Note: If you suffer from heart disease or raised blood pressure you should stay clear of isometric training. During muscular contractions in this form of exercise, blood pressure can rise quite profoundly!

Isotonic; This literally means equal tension. Isotonic contraction is a contraction in which the tension remains constant as the muscle shortens or lengthens. The simplest example of this is where a dumbbell is lifted from the ground and used to perform an exercise. The tension generated by the dumbbell is now the constant, or in other words if you pick up a 5 pound dumbbell it weighs 5 pound whatever you do with it. However, it should be remembered that momentum often has a profound effect on the actual resistance to the muscle (SLOW DOWN!).

The elaborate cam systems seen on most modern weight training equipment allow for a more isotonic movement to be performed. The key to isotonic exercise is that although the weight is constant the speed of movement associated with the exercise is variable.

Isokinetic: This least known form of exercise is in contrast to the other forms in that it permits maximum muscle contraction throughout the full range of joint movement. It is often referred to as ‘accommodating resistance exercise’. The resistance is variable in proportion to the change in muscular capability at every point in the range of motion. The variation is controlled so that at all times it equals the product of the muscular strength.

Sound complicated? It IS! The MAIN drawback to this type of exercise is complexity, and expense. In most cases, an "active dynamometer" is required. In this type of exercise the speed is controlled whilst resistance is variable according to the amount of force throughout the range of movement. No matter how much force the individual applies the speed does not change.

The other way to engage in this type of exercise is to work with a "buddy" or Personal Trainer to provide varied resistance during exercise movements. This requires a lot of education and experience on the part of the Trainer.

Well, after ALL this information, the choice is really pretty simple. Our recommendation: stay with Isotonic exercises… they are the most effective, and easiest to use (although somewhat risky without proper form and technique… see Table). If you’re working with an experienced Trainer, ask him or her to incorporate some Isometric and/or Isokinetic exercises in your workouts.

As usual, diversity rules!

Be sure to catch next weeks column on how to most effectively spend your money on fitness!

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