The Role of MVIC: How Physical Therapists Choose Exercises

Have you ever looked at an exercise from your physical therapist and wondered, “Why am I doing this?”

Maybe the movement seems too simple. Maybe it does not look anything like the activity you are trying to return to. Or maybe you do not feel it in the exact muscle your therapist says you are training.

Physical therapists choose exercises in several ways. We consider what you need to get back to doing, what we find during your evaluation, how your body responds, and what we have learned through training and experience.

We also use research to answer a more specific question: Does this exercise actually recruit the muscle we are trying to strengthen?

One way researchers answer that question is through MVIC.

What Does MVIC Mean?

MVIC stands for maximum voluntary isometric contraction.

The name sounds complicated, but the basic idea is simple.

Researchers first have someone contract a specific muscle as hard as possible without moving the joint. They measure the muscle’s electrical activity using electromyography, or EMG. That maximum effort becomes the reference point.

They then measure the same muscle during an exercise and compare the two readings. The exercise is reported as a percentage of MVIC.

For example, if an exercise produces 60% MVIC, the muscle activity during that exercise reached approximately 60% of the activity recorded during the maximum test.

Your physical therapist is probably not attaching electrodes and measuring MVIC during every treatment session. Instead, therapists can use published research to understand which exercises tend to create more or less activity in particular muscles.

Why Not Just Choose an Exercise That Looks Functional?

Functional exercises are important. If your goal is to climb stairs, run, lift overhead, or return to a sport, your rehabilitation should eventually prepare you for that activity.

But sometimes a larger movement allows a weak muscle to hide.

Other muscles may take over. You may shift your weight, rotate your body, arch your back, or change the movement without realizing it. You can complete the task, but not necessarily with the strategy your therapist wants to improve.

That is why a program may temporarily include an exercise that looks less functional. Your therapist may be trying to place a particular muscle in a position where it has to contribute and where compensations are easier to see.

Once that muscle becomes stronger and easier to control, the exercise can be progressed back toward standing, speed, balance, lifting, running, or sport.

Why “I Don’t Feel It” Does Not Tell the Whole Story

Patient feedback matters. Pain, effort, fatigue, confidence, and how you feel afterward all help us decide whether an exercise is appropriate.

But your ability to feel a muscle is not a perfect measurement of how much that muscle is working.

You may feel a burning sensation in the front of your hip while several muscles around the hip are active. You may feel general shoulder fatigue without knowing whether most of the demand is coming from the rotator cuff or the larger deltoid muscle.

Some people are very aware of individual muscles working. Others are not. Neither response automatically tells us whether the exercise is effective.

MVIC research gives us another piece of information. It can show that an exercise strongly recruits the intended muscle even when you do not clearly feel it.

A Glute-Med Example

The gluteus medius is located along the outside of the hip. It helps control the pelvis when you walk, climb stairs, run, or stand on one leg.

Several common exercises target this muscle, but they do not all create the same demand:

• A standard clamshell may produce approximately 33–40% MVIC.

• A side-lying leg raise may produce approximately 70–81% MVIC.

• A side plank with hip abduction may reach approximately 89–103% MVIC.

This does not mean everyone should skip directly to the side plank. The clamshell may be the right place to begin when someone needs a supported position and is still learning to control the pelvis. The side-lying leg raise provides a larger challenge. The side plank adds significant strength and full-body stability demands.

The numbers help us understand the exercises. The therapist still has to choose the right one for the person.

A Rotator-Cuff Example

Consider side-lying shoulder external rotation: lying on your side with your elbow against your body and rotating the forearm upward.

It does not look like throwing a ball, reaching into a cabinet, or lifting something overhead. But research has shown that it can create substantial activity in two important rotator-cuff muscles: approximately 62% MVIC in the infraspinatus and 67% in the teres minor.

That makes it a useful way to strengthen part of the rotator cuff in a controlled position.

A different shoulder exercise may produce more total muscle activity but also recruit the deltoid much more heavily. That may be useful later, but it may not be the best choice when the immediate goal is more focused rotator-cuff work.

The exercise that looks more difficult is not always the exercise that best targets the current problem.

MVIC Helps Identify the Exercise—Your PT Builds the Progression

Knowing that an exercise recruits a muscle is only the beginning.

Your therapist can make the same movement easier or harder by changing:

• Your body position.

• The amount of resistance.

• The length of the lever.

• The range of motion.

• How slowly you lower.

• How long you hold the position.

• The amount of balance or support available.

• The speed and complexity of the movement.

Early exercises may emphasize control or an isometric hold. The next stage may add resistance or slow eccentric loading, which challenges the muscle as it lengthens. Later progressions may include standing movements, faster reactions, jumping, throwing, or plyometrics.

The original exercise does not have to resemble your final activity. It needs to build something that will eventually contribute to that activity.

Your PT Should Be Able to Explain Why

There is rarely one perfect exercise for everyone. The appropriate exercise depends on your symptoms, strength, movement control, goals, and stage of recovery.

Your physical therapist should be able to explain:

• Which muscle or movement the exercise is intended to train.

• Why it is appropriate for you right now.

• What compensation the therapist is watching for.

• How the exercise will be progressed.

• How it connects to what you ultimately want to do.

MVIC is not the only reason to choose an exercise, and the exercise with the highest percentage is not automatically the best. MVIC is one tool that helps us know whether the intended muscle is participating and how demanding one exercise may be compared with another.

The therapist’s job is to combine that information with your feedback, your movement, and your goals—then build the exercise from an appropriate starting point toward real-world function.

In our next article, we will use the glute med as an example and progress from clamshells and side-lying leg raises to band side steps and challenging side-plank variations.

At SB Physio, our physical therapists provide one-on-one care, allowing us to watch how you move, adjust your exercises, and explain why each one belongs in your program.

Have questions about which exercises belong in your rehabilitation program? Click here to schedule an evaluation.

Disclaimer: This article is intended for educational purposes only and should not be considered medical advice, diagnosis, or treatment recommendations. Every individual and every condition is unique. The information presented here should not replace an evaluation by a qualified healthcare professional. Reading this article does not establish a provider-patient relationship with SB Physio or its clinicians.