Muscle Strength Scale in Physical Therapy

Dynamometer Hand Grip Strength Test
BanksPhotos/E+/Getty Images
In This Article

The muscle strength grading scale is often used by your physical therapist to determine how a muscle or group of muscles is working. Your PT may test your muscle strength during your physical therapy evaluation and assessment and at regular intervals during your rehab to determine your progress in therapy.

Measuring muscle strength may be an important component in your physical therapy evaluation and assessment. Your PT may measure your strength if he or she feels that weakness or decreased muscle function may be a cause of your pain or limited functional mobility.

If you are having pain or difficulty with normal movement, your doctor may refer you to physical therapy for treatment. You may also choose to attend physical therapy through self-referral if your state allows direct access.

Your physical therapy plan typically starts with an evaluation, during which your physical therapist will collect information and data to help make a diagnosis and customize the best treatment strategy for your condition. Some of these tests may measure the range of motion, gait, flexibility, balance, mobility, and strength.

What Is Strength?

Strength is the ability of your muscle(s) to contract and produce force. A lot of things can limit muscle strength, such as surgery, illness or injury. Lack of physical exercise can also decrease your strength, which can lead to repetitive strain injuries. If your muscles lack strength, then you may have a difficult time with basic functional mobility.

How Is Strength Measured?

Manual muscle-testing and the use of a dynamometer are the most common methods to measure strength. Understanding these methods of strength testing and learning the muscle strength scale can help you track your progress in physical therapy. If your PT has a solid baseline of your muscle strength, he or she can determine if you are getting better and can ensure that you are doing the right things for your condition.

Manual Muscle Testing

Manual muscle testing is the most popular way to test strength. Your physical therapist will push on your body in specific directions while you resist the pressure. A score or grade is then assigned, depending on how much you were able to resist the pressure. Strength is measured on a five-point scale:

  • 0/5. A 0/5 score means that you are unable to create any visible or noticeable contraction in a specific muscle. This occurs when a muscle is paralyzed, such as after a stroke, spinal cord injury, or cervical or lumbar radiculopathy. Sometimes pain can prevent a muscle from contracting at all.
  • 1/5. A grade of 1/5 occurs when muscle contraction is noted but no movement occurs. The muscle is not strong enough to lift the particular body part against gravity or move it when in a gravity-reduced position. A small flicker of muscle contraction may be palpated, or felt, during testing.
  • 2/5. This muscle-strength grade is assigned when your muscle can contract but cannot move the body part fully against gravity. When gravity is reduced or eliminated during a change in body position, the muscle is able to move the body part through its full range of motion.
  • 3/5. A 3/5 grade means that you are able to fully contract your muscle and move your body part through its full range of motion against the force of gravity. But when resistance is applied, the muscle is unable to maintain the contraction.
  • 4/5. A 4/5 grade indicates that the muscle yields to maximum resistance. The muscle is able to contract and provide some resistance, but when your physical therapist presses on the body part, the muscle is unable to maintain the contraction.
  • 5/5. This means the muscle is functioning normally and is able to maintain its position even when maximum resistance is applied.

Occasionally your physical therapist may grade your muscle strength in half increments, using the + or - sign. A grade of 4+/5 indicates that your muscle yielded to maximum resistance, but was able to provide some resistance during the testing. A 4-/5 grade means that your muscle was not able to provide much resistance at all during testing. The use of these incremental grades is subjective, which makes them unreliable.

Manual muscle testing is popular because it is inexpensive and readily available. It is easy to do and you do not need any special equipment to do it. The method cannot detect small changes in strength that may occur as you work hard in physical therapy to improve your condition.

Dynamometer Testing

Another method to measure strength is by using a device called a dynamometer. Your physical therapist will hold the dynamometer as you press it. The device will electronically display the amount of force you are exerting in pounds or kilograms. Smaller, handheld dynamometers can measure grip strength; even smaller pinch-grip dynamometers can measure your pinch strength.​

A dynamometer can test for small changes in your ability to contract a specific muscle or muscle group. One limitation, however, is that the standard device can be quite expensive and bulky, making it difficult to use in the home-care setting.

A Word From Verywell

If you are experiencing pain or weakness that results in a loss of functional mobility, you may benefit from visiting a PT for an assessment. He or she may measure your strength during the examination. Strength measurements can help your physical therapist determine the cause of your problem and devise an effective treatment plan. Increasing your strength during physical therapy can lead to real functional improvements in your health.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  • Bohannon, Richard W. Reliability of manual muscle testing: A systematic reviewIsokinetics and Exercise Science, 2018, pp. 1–8., doi:10.3233/ies-182178.

  • O'Sullivan, S. B., & Schmitz, T. (1994). Physical rehabilitation, assessment and treatment. (3 ed.). Philadelphia: F. A. Davis Company.
Related Articles