One-Repetition Maximum (1RM)

A one-repetition maximum, or 1RM, is the greatest load a person can successfully lift once through the required range of motion for a specified resistance exercise using the defined technique. It is an exercise-specific measure of dynamic maximal strength rather than a single property that is identical across all movements .¹

A 1RM test usually involves progressively heavier attempts separated by recovery until the heaviest successful repetition is identified. Research indicates that properly conducted 1RM testing generally has good to excellent test-retest reliability across many common exercises and populations, although familiarization, technique, equipment, and testing procedures can still influence the result .¹

The 1RM is also used as a reference for prescribing training load, with resistance expressed as a percentage of 1RM. That percentage describes relative external load, not the full difficulty of a set. Repetition number, proximity to failure, movement velocity, rest intervals, and exercise choice also shape training intensity and fatigue .²

A 1RM value is usually reported for a named exercise and testing setup, such as a barbell squat or machine press. Changes in technique rules, range of motion, equipment, or assistance can change the result and reduce comparability across testing sessions .¹