How Effective is Isometrics?

Is Isometrics better than Isotonics? 

Are isometric exercises a good way to achieve fitness?  Or are they more suitable for building strength?  And where to they stand relative to isotonics?

First, let's explain the difference between the two terms. In an isometric exercise the muscle stays the same length regardless of the amount of force being used, as, for example, when trying to lift something that is too heavy to move, or when (as in the picture below) the muscle is trying to contract but is being prevented from doing so by an equalizing pressure from another muscle.  In an isotonic exercise the muscle shortens when something is being lifted, as for example, the raising of the leg in the second picture.  The isometric exercise is generally regarded as more effective for maintaining muscle strength than for building muscle strength, hence it may be recommended for purposes of rehabilitation.  The isotonic exercise is the one people generally recognise as being used for fitness, such as playing ball games or weight-lifting.

Both forms of muscle contraction have their benefits.  A physical fitness programme ideally would include both.

40 years ago a book on Isometrics written by Henry Wittenberg, who had been the United States Olympic team wrestling coach. promised "Total fitness without effort, using only seconds of motionless exercise each day."  The back cover even suggested, "the next time you are driving to work, with your right hand pull hard on the steering wheel to the right; at the same time, with you left hand pull hard on the wheel to your left.  Feel your stomach muscles tighten.  You have just exercised -- the easy way!"

A recent online description of isometric exercises describes these as popular among fitness enthusiasts for several reasons. "They can be conveniently performed any time and anywhere, whether you're at home, in your workplace or even when you're driving. Another advantage of isometric exercises is that they can be done without the use of expensive equipment. They are effective for sculpting and strengthening the body, and they pose very little health threat to the body."

So one wonders why a system so simple yet effective, should have enjoyed an enormous success for a considerable period of time, with all sorts of inventive devices, such as the "bullworker",  being offered to support this activity, and then be superseded by the alternative (isotonic) exercise that generally is more expensive and less convenient in terms of cost and location.

A typical "bullworker" advertisement.

We suspect that this may be due, at least in part, to awareness of problems that might arise when isometric exercise is practised by people for whom it might be medically inappropriate, or where alternative - specifically isotonic - regimens were being recommended by the medical and alternative medicine professions.  One of the most problematic areas in isometrics is their ability to increase blood pressure dramatically and thus make them inappropriately dangerous for people suffering from hypertension.  Whereas certain isotonic exercises, particularly those that can be practised easily and daily - such as walking - would be more beneficial to health.

Let's go through it again, because it really is not simply a matter of "whether - or", nor is it simply a question of "which is better?".  Both forms of exercise (or - more precisely - contractions) have benefits; both have potential hazards.  As with so much else in life, the things that are good for us very often contain a corollary if they are not practised appropriately, as recommended, or to excess.

An isometric contraction is the action of a muscle or a group of muscles against an immovable object, or against each other, creating tension without motion.  A good illustration of this principle would be the expression "pulling oneself up by the bootstraps".  The most simple of all isometric exercises is probably the one illustrated above: merely pressing palms together in front of the chest and maintaining the position for several seconds.  Since the muscles in this exercise are working within their own limits, there is no risk of injury.  On the other hand, because the results of such isometric contractions are less obvious than those of isotonic exercises, there may be a tendency for people to over-engage in them.  And as we said above, a potential hazard is provided by anything practised to excess.

There are two types of isometric exercise. One utilizes the body's own muscles to exert force on a fixed object, such as a wall. The other places a muscle in a contracted position for a period of time. A good example is to have a seat in a chair, extend your legs one at a time and hold the position for 3-6 seconds. While this type of exercise will not increase muscle mass as quickly as weight-bearing exercises, it will serve to prevent muscle and bone loss and increase strength.

Isotonic contractions on the other hand involve repeating a fixed set of movements while placing strain on a particular muscle.  This occurs, for example, when working out with weights and is most effective at training large muscles. The results and effects are more speedily and readily noticeable than those of isometric training.  At the same time it is also much easier to injure oneself by training for too prolonged a time or with equipment, such as weights, that is too heavy or difficult.  Simple examples of isotonic exercises are push-ups, sit-ups, chest presses and squats.  Most gym exercises are isotonic.

It is easier to recognise excessive isotonic exercise than excessive isometric exercise.  Since isometric exercises do not involve any movement the body does not provide the same warning signals as in isotonic exercise, but since the isometric contractions can significantly increase blood pressure great care should be taken when performing them.  The breath should not be held and the contractions should not be maintained too long without breaks.  It is possible that this potential danger is the reason why this system of exercising fell into disrepute. This is just conjecture!  But it is supported by the following internet quote 

"Regular exercise is typically considered safe for most individuals, and the benefits usually outweigh the dangers or risks. But if you and your doctor determine that isometric exercise is dangerous based on your health history, consider alternatives that include more dynamic or active movements. Dynamic exercise is a low-resistance movement or workout that involves repetition and performance. Engaging in a dynamic sport or workout on a regular basis will increase your endurance, and your doctor may recommend it as a safe alternative if you have high blood pressure or heart problems. Walking, swimming, aerobics and elliptical training are a few examples of dynamic exercise."

On the other hand, the Internet has also provided the following positive example (although it does conclude with a mild injunction) from a female "trainer":