manual muscle testing
When a physical therapist asks you to 'push against my hand as hard as you can' and then resists you, they are doing something deceptively simple: judging how strong a muscle is using only their own hands and a standard scale. This is manual muscle testing, usually shortened to MMT. It needs no machine — just careful positioning, clear instructions, and a trained sense of how much resistance a healthy muscle should overcome.
In a typical test, the examiner isolates one muscle or muscle group, positions the limb so gravity is either helping, neutral, or opposing, and asks the person to hold or move against the examiner's pressure. The result is graded on a 0-to-5 scale: 0 means no detectable contraction, 3 means the muscle can just move the limb through its full range against gravity but no added resistance, and 5 means normal strength. The examiner tests both sides so the weaker can be compared with the stronger, and follows a head-to-toe order so nothing is missed. Patterns matter as much as single grades — weakness in one nerve's muscles points to a nerve injury, weakness on one side of the body points to a stroke, and weakness in the muscles closest to the trunk points to certain muscle diseases.
MMT is one of the workhorses of the rehabilitation examination because muscle strength underlies almost everything: standing up from a chair, gripping a cup, holding the head upright. Its great virtue is that it is cheap, quick, and portable. Its honest limitation is that it is subjective and fairly coarse, especially at the top of the scale — a strong examiner may grade a powerful athlete '5' even when the athlete has lost real strength, because the examiner simply cannot overcome them by hand. For finer or research-grade measurement, instrumented tools like a hand-held dynamometer are used instead.
A man with a foot drop is tested: the muscles that lift the foot grade 2 of 5 (they can move only when gravity is taken away), while the calf grades 5. That isolated weakness, traced along one nerve's territory, points the team toward a specific nerve problem rather than a general loss of strength.
Where the weakness is can matter as much as how weak.
MMT is subjective and least reliable at the high end: a 5/5 by hand does not rule out real strength loss in a strong person, because the examiner may simply be unable to break the muscle by hand. Dynamometry gives finer numbers when needed.