In fitness, what does the acronym 'ROM' stand for?

In fitness, ROM stands for range of motion—the amount a joint can move through its available movement pattern.

Range of motion may be measured in degrees and differs from person to person. It depends on factors such as joint structure, muscle length, connective-tissue flexibility, injury history, age, and the activity being performed. For example, a shoulder generally has a wider movement range than a knee, while a knee mainly bends and straightens.

Fitness and rehabilitation professionals often distinguish active ROM from passive ROM. Active range is produced by a person’s own muscles; passive range is reached with assistance from another person or an external force. ROM is not the same as repetition maximum, another fitness abbreviation commonly written as RM. Improving mobility can help movement quality, but forcing a joint beyond a safe range can cause pain or injury.