Muscle imbalance

Muscle imbalance is a loose term for a difference between muscles that are meant to work together: one side of the body stronger than the other, or one muscle group tighter, weaker or more active than the group that opposes it. Clinicians use it to explain posture and pain, most famously in Vladimir Janda’s “crossed syndromes”, which describe pairs of tight and weak muscles crossing the upper and lower body (Russin et al., 2026).

What does muscle imbalance mean in practice?

Because it can be measured in several ways, the term covers quite different things. Three examples show how differently it is used, and how mixed the results are:

• Side-to-side strength. In 163 college athletes, women whose hip extensor strength differed more between the left and right sides were more likely to need treatment for low back pain over the next year. There was no such link in men, and only 13 athletes needed treatment in total, so the numbers are small (Nadler et al., 2001).
• Muscle length. “Tight hip flexors” are a classic example. In 118 adults, people with low back pain had slightly shorter hip flexors, but once other factors were considered, back pain was not independently linked with hip flexor length (Eimiller et al., 2026).
• Which muscles do the work. In people with neck pain, the deep neck flexors were less active and there was a trend towards more activity in the sternocleidomastoid (Falla et al., 2004). Office workers with neck pain also had an upper trapezius that struggled to switch off after tasks (Johnston et al., 2008).

Findings of this third kind come up repeatedly in neck pain research. They are also the hardest to interpret: the authors of the office worker study said plainly that they could not tell whether the change was a source of the pain or a consequence of it.

Common misunderstandings about muscle imbalance

“My posture shows I have an imbalance, and that is why I hurt”

Posture and pain are less tightly linked than the idea suggests. Adults with neck pain do have more forward head posture on average than adults without it, but in adolescents there was no such difference (Mahmoud et al., 2019). For the lower back, a review of 41 systematic reviews found associations with posture and sitting but no consensus that they cause pain (Swain et al., 2020).

“Fix the imbalance and the pain will go”

This is the claim with the weakest support. A 2026 meta-analysis of 28 trials with 901 people with upper crossed syndrome found that corrective exercise programmes clearly changed posture measurements, such as the angle of the head and shoulders. The effects on pain, function, muscle activity and balance were inconclusive (Khorramroo et al., 2026).

“So exercise doesn’t matter”

It does, just not necessarily for the reason given. In a trial of 198 working adults with frequent neck and shoulder pain, two minutes a day of strengthening on workdays reduced pain and tenderness compared with health information alone (Andersen et al., 2011). The exercise in that trial was progressive strengthening, not the correction of a particular imbalance. More on short sessions is in Is two minutes of exercise enough?, and on stretching in Do stretches help neck pain from desk work?

Related terms

Upper crossed syndrome is the best-known muscle imbalance model for desk workers. For the posture it is usually attached to, see forward head posture, and for the lower back, lower back pain from sitting.

Bavelu’s stretching and mobility sessions for the neck, shoulders and back are designed and filmed by physiotherapists.