Muscle imbalance: what it is and why it’s important

At best, muscle imbalance will not allow you to perform at your optimum; at worst, it could cause an injury. Physio Caoimhe McNamara explains causes and treatment so you can stay in balance

Muscle imbalance: what it is and why it is important

What’s the difference between agonist and antagonist muscles?

In order for proper movement to occur muscles will often work in groups opposing each other. These muscle groups that work together, but in opposite directions (confusing I know!), are called antagonistic muscles. They will often  include one group of muscles contracting by shortening and pulling (agonist), and the opposite group slowly lengthening to allow the movement to occur (antagonist). A common example of this is when we run and take a step through, our hamstrings will lengthen while our quadriceps will shorten to help our leg to move forwards.


What is muscle imbalance?

It is quite common to have an imbalance in how these muscles work together, and you’ve guessed it, this is called a muscle imbalance. It can be related to an imbalance in control, strength or power between these antagonistic muscle groups.

What causes a muscle imbalance?

A muscle imbalance can occur for a number of different reasons:

  • Posture and certain activities of daily life
  • Poor underlying biomechanics
  • Unbalanced strengthening/exercise programme
  • Reliance on a dominant side
  • Poorly fitting equipment (ie. an incorrectly sized bike, or poorly fitting trainers)
  • Pain

A muscle imbalance may present itself by a plateau in performance, pain or injury. While the cause may be multifaceted, one thing is clear – trying to correct any muscle imbalance is key to preventing injury and performing to the best of your ability.

How do you diagnose muscle imbalance?

To address a muscle imbalance,  you must first identify the location of the imbalance. This can be done in an assessment with a physiotherapist. They may look for the following:

  • A visible difference in size of the muscle tissue
  • Your resting posture, as well as your posture while exercising (ie. running on the treadmill, or cycling on an exercise bike).
  • Areas of soreness/pain on palpation
  • Strength deficits – both looking at endurance and power
  • Motor control deficits
  • Movement restrictions

They may ask you to do some functional movement screening tests that will often challenge one side of your body at a time. This is the easiest way to identify the main differences between left and right. If we stick with the example of a lower limb muscle imbalance,  some of these tests would be:

  • Single leg stand: to assess single leg control and balance
  • Single leg squat: to assess hip and knee control
  • Single leg heel raises  to assess calf strength
  • Single leg hops: to assess calf power, landing control
  • Single leg bridges: to assess lumbopelvic control, glute strength
  • Single leg hip hinges: to assess single leg balance, hamstring control and length

They may even video you doing these tests, so that you can both look back over the videos on a slowed replay to identify any differences not seen in real time.

How do you treat and fix muscle imbalance?

Once you have identified areas of weakness and restriction, an appropriate rehab programme will be created to help you balance out that imbalance. These handy videos can be a useful tool to look back on to see how far you’ve come in your rehab journey.

If you have just started a new training block, or have your eyes set on a new performance goal,  why not be proactive and book a physiotherapy assessment to catch any underlying muscle imbalances before they cause trouble. Prevention is always better than cure!

If you have any concerns at all, like with any health issue, always seek medical advice from a qualified medical practitioner, whether that’s a doctor or physiotherapist. 


Caoimhe McNamara is consultant physiotherapist at Six Physio