Isokinetic exercise is a type of strength training in which the speed of the movement remains constant, but the resistance varies. People tend to use specialized exercise machines to perform these exercises.

When using an isokinetic exercise machine, a person will maintain a steady rate of motion. However, as they exert more force, the resistance increases.

These exercises can improve a person’s strength and range of motion. Due to this, a common use of isokinetic exercises is to help regain mobility after an injury or illness.

A physical therapist can help an individual develop an isokinetic exercise plan that allows them to build strength safely and effectively.

This article explains how isokinetic exercise works, its benefits, and more.

A person using an isokinetic exercise machine.Share on Pinterest

Isokinetic exercise is a form of resistance training. It allows the targeted muscle to work at full strength while maintaining a constant speed.

A person usually needs to use a special machine to perform these exercises. The exercise machine helps isolate the area they are trying to strengthen and control their movement.

Typically, an individual will do isokinetic muscle contractions as part of an injury rehabilitation program.

A doctor or physical therapist will set the machine to the correct speed, range of motion, and resistance. This set speed allows the muscles to contract and shorten at a constant rate, which results in movements called isokinetic contractions.

Physical therapists often use isokinetic exercise as a relatively safe and effective way to strengthen certain muscles in a person recovering from an injury.

Some of its benefits include:

  • A person can experience resistance throughout a joint’s entire range of motion.
  • The controlled resistance and speed reduce the risk of injury.
  • A physical therapist can definitively measure a person’s progress.

This type of exercise may also be a better form of muscle recovery than other types. According to a 2017 study, isokinetic exercises were more effective in improving functional performance than isometric and isotonic exercises.

Additionally, because physical therapists can modify isokinetic exercises to suit people of different abilities, this type of training has a broad appeal. A 2020 study showed that in athletes with lower back pain, it was more effective than standard rehabilitation exercises.

Research also showed that a 12-week isokinetic program could increase muscle strength and balance in children with Down’s syndrome and might be better than traditional physical therapy for these individuals.

Isokinetic exercise is useful for people recovering from a variety of injuries and illnesses because it is possible to tailor it to people of all abilities. People who may particularly benefit from it include those with:

  • osteoarthritis
  • stroke
  • obesity
  • muscle injury

People often use the terms isometric, isotonic, and isokinetic when talking about muscle rehabilitation. Each has different uses and benefits, and most exercise plans contain a combination of the three.


In isometric exercises, the muscles do not shorten or lengthen. Instead, they work without bending a joint.

A person may also refer to these movements as static exercises. The muscle works to hold a position that may be strenuous. For example, holding the body in a plank position is an isometric exercise.


Isotonic exercises are those that put a consistent tension on the muscles while moving them through a full range of motion.

Squats are an example of an isotonic exercise. While doing a squat, the hips and knees move with the weight of the body, providing unchanging resistance.

Pros and cons of each

The following is an easy way to remember the differences between the three types of exercise:

  • Isokinetic involves the same speed.
  • Isometric involves the same length.
  • Isotonic involves the same tension.

Each type of exercise produces gains in muscle strength. Different types of exercise may work better for different people with varied abilities and goals.

Very few studies have explored the differences in the effectiveness of these three types of movement.

However, a small 2017 study, which included 30 males, indicated that they are not equally beneficial for achieving the same goals. It compared the effects of each type of exercise on the quadriceps muscle — the one at the front of the thigh — and functional performance.

The researchers concluded that isokinetic workouts were the best at increasing isokinetic strength, while isotonic exercise was better for improving functional performance. Isometric and isotonic testing showed that there was no difference in strength gains.

However, larger studies with more diverse participants are necessary to verify the advantages of one type of exercise over another.

One of the major benefits of isokinetic exercise is its apparent lack of risks. It has a very low injury risk, making it good for people recovering from existing injuries.

However, the authors of an older 2013 study expressed concern about people engaging in strenuous endurance exercise using an isokinetic machine. They suggested that good heart function might be necessary to avoid potential heart attack in those with a predisposition to this cardiovascular event because the workouts produced a degree of oxidative stress.

However, they noted that this exercise was otherwise safe for healthy participants.

It is important to note that any form of strenuous exercise can potentially be dangerous to individuals with an underlying cardiovascular condition. A person should contact a doctor before starting a new workout plan, and if they are undergoing rehabilitation from an injury or illness, they should follow their physical therapist’s instructions.

Usually, isokinetic exercise will take place on a special machine under the guidance of a physical therapist, who will show the person how to perform a movement safely. After a person has gained strength, they may be able to do these exercises on their own.

When doing any form of resistance training, a person should:

  • Check with a doctor: Before starting a new exercise program, a person should contact a doctor.
  • Start slowly: People should increase the intensity of their routine and the repetitions gradually. For those who wish to exercise on a treadmill or stationary bike, the Centers for Disease Control and Prevention (CDC) recommend setting a goal of 30 minutes of exercise on 5 days of the week.
  • Stay hydrated: A person should ensure that they drink sufficient water before, during, and after a workout to replace any fluid lost during exercise. If they feel thirsty at any point, they are not drinking enough.
  • Stop exercise if problems arise: It is important to stop if an exercise causes pain. People should also take a break if they are tired, as fatigue can cause poor form, which may lead to injury.
  • Get help if necessary: The machines that provide isokinetic exercise can be confusing. It is advisable to seek advice from a physical therapist before starting a workout plan.
  • Warm up and stretch before a workout: According to a 2018 study, doing a warmup that includes stretching before an isokinetic workout is beneficial.

Isokinetic exercise involves performing movements at a constant speed with varying resistance. It can increase muscle strength and range of motion.

As this form of training poses little risk for injury, people often use it to aid recovery after injury or illness.

This form of movement usually uses complex exercise machines. A person may benefit from seeking the help of a physical therapist to get started.