Writing Sample 4 - Isotonic vs Isometric vs Isokinetic Exercise: Explained

Jack Rosser - PT, BSc, MCSP, HCPC, FMPA.

Every hour of every day we move through countless different motions that require the muscles to contract and relax, all in very different ways.

For those of us looking to improve our athletic performance and physique, it is imperative that we understand the different types of muscle contractions available to us, and how to use them.

When it comes to the three I’s (Isometric, Isotonic, Isokinetic) there is often some confusion around these terms and what they achieve individually.

In this article, we aim to break that confusion and explain the differences…



Isometric

Isotonic

Isokinetic

Static position. No shortening or lengthening of muscle tissues. Joint angle stays fixed. (eg. Plank)

Dynamic movement. Muscles shorten and lengthen. Using a fixed weight throughout the whole movement. (eg. Dumbell Bicep Curl)

Dynamic movement. Muscles shorten and lengthen. Variable tension throughout the movement. (eg. Stationary bike)




What is Isometric Contraction?

Isometric muscle contractions occur when the muscles engaged stay at the same length, tension, and speed. They may also be referred to as static exercises. Throughout an isometric exercise, the joint angle remains static instead of changing during the movement.

Essentially, an isometric contraction is when a muscle is engaged without the joint moving.


Benefits of Isometric Exercises

As a rehabilitation tool, this kind of exercise has numerous benefits. Not only are they a low load exercise, they also help to maintain strength, stability and endurance around a joint.

We can slowly increase and self-dose the level of resistance based on what we can tolerate, as opposed to biting off more than we can chew with variable free-weight loading.

It has been well documented and re-affirmed in recent studies that early isometric loading has both a pain-relieving effect in acute tendon irritation, including but not limited to the knee, hip and shoulder.


It also serves as a protective response for soft tissue injuries such as muscle strains.

A recent study incorporating early isometric loading as part of a comprehensive hamstring rehab program for elite track and field athletes demonstrated increased tendon adaptation, faster return to full training, and lower injury recurrence rates (Pollock et al., 2022).

It has also been theorized more recently that Isometric loading can have positive effects on decreasing blood pressure, making it a very useful tool for those not able to engage in higher-intensity exercise, although it is worth noting that this still needs more research to verify the claims (Edwards et al., 2022).


Examples of Isometric Exercises You Can Do

Isometric exercises are easy and accessible, making them possible to do anywhere you go with little or no equipment. Some types of isometric exercise you could try:

– Push up hold

– Squat hold

– Yoga Ball/ Step Bridge Holds

– Side plank holds


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