Biodex isotonic muscle testing

What is Biodex isotonic muscle testing?

The Biodex is an isokinetic muscle testing machine, used to help with pre-season screening, injury prevention, athletic performance enhancement, prehabilitation, and rehabilitation for all peripheral joints – hip, knee, ankle, shoulder, elbow, and wrist.

An isokinetic muscle contraction is one in which the muscle contracts and shortens at a constant rate of speed. Specialised testing equipment allows healthcare professionals valuable information regarding strength deficits and muscle imbalances that may predispose a particular joint to further injury. Information obtained through the tests provides your therapist and your consultant with objective data that can be used to monitor your progress. This data is used to establish realistic sgoals to determine when it is safe to return to sport and to work.

How does it work?

The Biodex System 4 Pro is an Isokinetic Muscle Testing Dynamometer, a machine for testing isolated muscle groups. The limb to be tested is made to move through a specified range of motion and to work at a specified level in a specified way. All of this is pre-programmed and controlled by the therapist running the test. The effort involved in this is recorded by the machine and a detailed report created. The report is based on objective data that can be used to highlight specific problems and also, indicate where treatment needs to be focussed.

Use of the Biodex can help at different stages of your recovery to aid with your healing:

  • Initially, following the injury, the Biodex can be used to passively move your limb through range. This essentially means the machine is doing the movement for you, so you are less likely to have pain as you are not using your own muscles. This can aid with swelling management and regaining active range of motion.
  • As you move from the acute to the sub-acute healing period, you can start to use the machine in active-assisted mode. This allows you to start developing your muscle strength as you are able to work at a level that is tolerable to you.
  • Once you are more comfortable and the inflammation has started to ease, you can start to use other modes, such as isometric, submaximal concentric and eccentric. These allow you test for specific muscle group weakness and also to target your treatment, allowing you to restore strength and neuromuscular control to the affected limb.
  • After you have moved into the final repair phase, you may start to work at safe exercise speeds in isokinetic concentric/concentric mode. This will aid with proprioception, muscular acceleration and deceleration.

What are the common injuries/symptoms that the Biodex can help with?

The Biodex is an isokinetic muscle testing machine that can be used to assess all peripheral joints. Lower limb joints include the hip, knee, and ankle, whilst upper limb joints include the shoulder, elbow, and wrist. It will isolate the muscles that work the joint and assess various aspects of how the muscle is working. This may include muscle strength and/or endurance. All the information is then collated by a software program linked to the machine, so that a report can be printed at the end of the assessment detailing the findings.

The Biodex is used by a range of healthcare professionals for a variety of reasons. Some use it to help with pre-season screening for sports clubs, in order to ensure their players are fit to return to play after periods of inactivity. Some use it to assess whether or not a joint has returned to full strength before the patient returns to sport or to work following an injury or surgery. It can also be used as a very specific treatment tool, allowing clinicians to control which range the patient is working in, how hard they are working, and in what way the muscle needs to work. Several university and research centres also use the Biodex for research purposes.

Is it suitable for me?

All members of the general public can access the Biodex System 4 Pro at Circle Reading physiotherapy department. This may be for a one-off assessment or, alternatively, as part of a rehabilitation package. If you are interested in any of the following, the Biodex can assist:

  • Return to sport
  • Preseason training/testing
  • Injury management/rehabilitation
  • Prehabilitation prior to surgery
  • Return to work/fitness to work
  • Improve sporting performance

What happens at the initial assessment appointment?

If you have not already had an assessment at CircleReading physiotherapy department, you will be asked to complete a health questionnaire detailing your current injuries, past medical history, and other relevant information. This is to ensure your therapist has all the necessary background information and details required to run the test. 

Your therapist will then take you to the Biodex machine and explain what it is and how it works, ensuring you have all the necessary information you need to make an informed decision before consenting to the test.

Once you have consented, you will then be seated in the chair or positioned by the dynamometer, the specific piece of equipment that measures muscle strength. Either of these may be altered in terms of height, length or position, in order to ensure you are in the correct position to start. If you are seated, you will have two straps placed crossways across your chest and one across your waist to ensure you are firmly strapped in and unable to ‘cheat’ during the test. It is very important to try and get the muscles to be tested isolated. That means, we don’t want you moving any other part of your body to try and influence the results.

If you are having both sides tested, your good limb will be placed into the attachment part first and fixed in position so it is stable. You will then be advised by your therapist to make certain movements. These movements may vary in terms of speed and resistance. Once your good limb has been tested, the same will be done on the affected side.

At the end of the test, your results will be saved and a printout made for your patient record. You will then be unstrapped from the machine.


“One piece of the equation I consider especially important is our Biodex Multi-Joint System. I really like it for the isokinetic capability, but I use it in the other modes as well. It is very useful as an exercise-based rehabilitation tool. I was always taught that exercise is the most important part of physio, and this is one of the few machines with a plug that actually provides exercise modality.

The Biodex Multi-Joint System is especially well suited to producing numerical data in terms of isolated muscle strength. The numbers generated during isokinetic tests have significant meaning and serve as pointers to help show where an injured patient is in terms of stability control and muscular control, providing insight as to when a patient can safely progress to more functional activities or even return to play.

Isokinetic testing, strengthening and rehabilitation are for us very much a preparation phase in terms of getting ready for active rehabilitation related to the game. It continues on as we progress through the rehabilitation regime and to actually playing. After the player returns to the field, it is used as a follow-up and strengthening mechanism for one to two years after many types of injury. The system is especially well-suited for lower limb rehabilitation.” - David Fevre, MSC, MCSP, SRP, Blackburn Rovers, Senior Physical Therapist for English Premier League Football Club, Blackburn

"We have been utilising our new isokinetic Biodex machine with a number of our patients undergoing rehabilitation. The assessment has been invaluable in our management planning, as this new approach provides a quantitative analysis of not only a patient's muscle deficits and imbalances, but also their predisposition to further injury. The Biodex machine allows clinicians to demonstrate to patients the areas to focus on in their rehabilitation and is an effective tool that provides insight as to when a patient can safely progress to more functional physical activities. The analysis allows us to track performance (range of motion, muscle strength) and I believe this helps to motivate the patient and encourage compliance." - Kate Hutchings, Circle Reading Sports Medicine Consultant

Case study

Brazil shoots for sixth world cup football championship. Will Biodex get an assist?

“With the World Cup coming to our country for the first time,” said Brazilian team physiotherapist, Luiz Alberto Rosan, “we’ve been able to make major upgrades to our facilities and equipment. With such a great opportunity, we’ve been very particular in making our choices. In the assessment, testing and rehab area, my staff and I have chosen the Biodex System 4 Pro Multi-Joint Testing System because it couples reliable, cutting-edge technology with exceptional dependability.”

Read the full story.