One-repetition maximum (1RM)

One-repetition maximum (1RM), often called a one rep max, is the most weight a client can lift for a single rep.^{1Zatsiorsky, Kraemer and Fry, Science and Practice of Strength Training, 3rd ed., p. 79.} A tested 1RM is considered the gold standard of strength assessment.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 632.} Other repetition maximums describe the most weight a client can lift for a given number of reps: a 3RM, for example, can be lifted only three times in a single set.^{1Zatsiorsky, Kraemer and Fry, Science and Practice of Strength Training, 3rd ed., p. 79.}

Programs often prescribe training loads as a percentage of 1RM, but the link between percentage and reps is rough.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 632.} It varies between people and exercises, and it holds only for a single set, since fatigue cuts the reps in later sets.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 632.}

In practice

• Untrained clients, clients who were recently injured and clients under medical supervision shouldn’t do a 1RM test.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 632.}
• When a test isn’t appropriate, estimate 1RM from a lower-rep maximum such as a 6RM or 10RM, ideally found within three testing sets.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 633.} Estimates from lighter loads can overstate the real 1RM.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 632.}
• As a rough guide, a 5RM is about 87% of 1RM and a 10RM about 75%.^{4Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 356.}