The difference between isometric, isotonic, and isokinetic exercises

• Isometric, isotonic, and isokinetic exercises refer to the different techniques for activating and strengthening muscles. 
• Isometric exercises, like planks, involve activating muscles with no movement.
• Isotonic exercises, like squats, involve activating muscles while moving the joints and applying a constant amount of weight. 
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We've all heard it before: Regular exercise is good for your health. In short: Any movement is better than no movement. 

But did you know that the way you move can bring different benefits to the body? Isometric, isotonic, and isokinetic training refers to the different ways you can activate and strengthen certain muscle groups.

Knowing the difference between these types of movements can help you create a functional exercise routine that fits your individual needs, and ultimately give you a leg-up in reaching your fitness goals. 

What is isometric exercise?

Isometric exercise is a type of low-impact exercise that activates muscles without movement. In isometric exercises, the muscles tense up, but the joints stay static. 

A prime example of an isometric exercise is holding your body in a plank position. While holding a plank position targets multiple muscle groups and strengthens your core,  there is no movement in the joints. 

Isometric exercises are ideal for maintaining strength, stability, and endurance. For instance, if you hold a low squat, that can help you hold that position for an extended period of time, but won't necessarily help you do more squats.

Isometric exercise is often recommended for people who are recovering from an injury, or who suffer from joint pain like arthritis. Evidence is growing that isometric exercise may help lower blood pressure as well.

"For years, we avoided [isometric exercise] in people with high blood pressure or heart disease," says Neil A. Smart, a professor of clinical exercise physiology at the University of New England. "But my work and others has recently shown clearly that isometrics is the best way to lower blood pressure with exercise."

In 2014, Smart and his colleagues published a review of 9 studies looking at isometric exercise and blood pressure. They found that both people with normal and high blood pressure who did isometric training lowered their systolic blood pressure by 7mm, which the researchers say could be enough to prevent an issue like a heart attack.

What is isotonic exercise?

While isometric exercise is all about engaging muscles with no movement, isotonic exercise involves putting a constant amount of weight or tension on your muscles while moving your joints through a full range of motion.

An example of an isotonic exercise is bicep curls, in which the amount of weight stays the same and your joints bend and straighten all the way. Other prime examples include resistance training exercises, including push-ups, pull-ups, and squats — where you use your body weight to tense up muscles and complete a full range of motion. 

Isotonic exercise can help strengthen and build muscles so that you can move through all types of motion with greater ease. "This type of training is what most people do in the gym and has benefits for preserving strength as we age," says Smart.

Isotonic exercise is especially useful for people at risk of or diagnosed with diabetes, Smart says, as it can help improve blood sugar regulation. A large 2017 study found that women who did strength-training exercises had a 30 percent lower rate of diabetes, compared with women who didn't train.

Isotonic exercise can also help build up bone density, which can be beneficial for people at risk of, or with, osteoporosis, a condition where bone mass is depleted. Studies show that athletes who lift weights have higher bone mass and density, compared with other types of athletes.

What about isokinetic exercise?

Isokinetic exercise is a type of workout that involves specialized machines and is not often used by the average person. "It is mostly used to train athletes to improve their running or throwing by improving the speed at which they can move their limb/body or a weight," Smart says.

The equipment used for isokinetic exercise, known as an isokinetic dynamometer, keeps your muscles moving at a consistent speed, which can then be raised with ongoing training.

This can help athletes like baseball pitchers or javelin throwers learn to use their maximum force at higher speeds, Smart says.

Isokinetic exercise can also be used to assess the muscle function of athletes or people with specific injuries.

How to remember the difference between isometric, isotonic, and isokinetic exercises

One way to remember the difference between isotonic, isometric, and isokinetic exercises is to look at the meaning of the original Greek roots of each word.

• Isometric means "same length," so that your muscles do not get longer or shorter by bending a joint.
• Isotonic means "same tension" so that the weight on your muscles stays the same.
• Isokinetic means "same speed" so that your muscles are contracting at the same speed throughout the workout.

Insider's takeaway

If you are looking to build strength or heal from an injury, understanding the benefits of isometric and isotonic movements can help you maximize your exercise routines. For most people, the combination of both is ideal for most workout plans.