Muscular Fitness: Isotonic, Isometric and Isokinetic Strength

Each person has a unique physical make-up and is stronger in some parts of the body than others. A tennis player, for instance, would expect her racket arm to be more muscular than her other arm, but a runner might not realize that one leg is weaker than the other. Strengthening a weaker leg may improve a runner’s form and even help to prevent injury. A sports medicine centre can test individual limb strength.

The various types of muscular fitness are isotonic, isokinetic and isometric strength and muscular endurance.

Isotonic strength

Also called dynamic strength, this kind of strength is the maximum force an individual can exert to lift a weight once. Isotonic strength can be measured using the free weights or resistance machinery in a gym. How much weight a muscle will support in a single lift is the measure of an individual’s isotonic strength. Leg strength, for example, can be measured on the leg press machine, while arm strength can be measured by lifting dumb bells.

Isokinetic strength

This is the force an individual can exert through a full range of movement, such as the circle made by the arms while swimming. Special electronic or hydraulic equipment is required to measure the isokinetic strength of individual muscles. Such equipment can also be used to rehabilitate athletes after they have sustained injuries.

Isometric strength

Also called static strength, isometric strength is the force an individual exerts against an immovable object. Isometric contractions raise blood pressure because people tend not to breathe correctly during the exercise, so they are rarely used in Western forms of fitness training. However, many of the Asanas (postures) performed in Yoga rely on isometric strength.

Correct breathing is central to Yoga practice so the blood pressure problem does not arise. Isometric strength testing requires specialist equipment and few sports centres offer this type of testing.

Muscular endurance

This is the length of time a person can continue to work particular muscles. It can be measured by how many repetitions of a particular task, such as press-ups or sit-ups, an individual can perform during a 1-minute test period. Muscular power and speed can also be measured by finding out how many skips she can perform and how quickly she can run 50 metres.


Traditional Eastern assessment of the state of an individual’s health relies heavily on developing an inner awareness of the body’s needs rather than on external testing to record fitness levels. The body is looked at as a whole, and the flow of energy (Qi) and blood (Xue) around the body is carefully monitored. In Chinese assessment techniques, for example, the practitioner takes note of the pallor and smell of the individual’s skin, the condition of her hair and the colour and condition of her tongue as indicators of her internal condition. The practitioner also listens to the sounds of the voice and body.

Pulse-taking forms a very important part of the Eastern health assessment. It takes longer than the Western technique and cannot be carried out by the untrained individual. The practitioner of Eastern medicine is highly trained in pulse-taking. Three fingers are used to measure 12 different pulses relating to the meridians (energy pathways) and organs of the body.

The pulse readings and observations allow the practitioner to piece together a picture of an individual’s health. Exercise in the form of Eastern techniques such as Tai Chi or Yoga may be recommended to increase the flow of energy around the body. Dietary remedies may also be suggested.