One-rep max1RM

The most weight you can lift for a single rep of an exercise.

Your one-rep max, written 1RM, is the heaviest load you can lift once with acceptable form on a given exercise. It is the reference point strength programmes are written against, because prescribing 75% of a max travels between people in a way that prescribing 80 kg does not.

You rarely need to test it. A set taken close to failure with a submaximal weight predicts it well through equations such as Epley or Brzycki, which convert reps and load into an estimate. The prediction is most accurate in the range of about 2 to 10 reps and drifts once you go much beyond that, because high rep performance depends as much on conditioning as on strength.

The estimate is also exercise specific and person specific. Someone with good endurance will out-rep their true max prediction; someone built for singles will undershoot it. Comparison studies of the various equations find them all reasonable and none of them exact, so treat the number as a working figure rather than a measurement.

Testing a true max has costs that programmes rarely account for: it is fatiguing, it needs a spotter and good technique under load, and the fatigue it leaves behind can eat into the following week's training. For most people training for muscle or general strength, there is no reason to do it.

It moves for two different reasons, which is worth knowing when it stalls. Early gains are largely neural, your nervous system learning to produce force efficiently in that pattern, and later gains come more from added muscle. Both are real strength; they just respond to different things.

In practice, estimate it from a hard set with our one rep max calculator, use it to set training percentages, and check it against our strength standards to see where you sit for your bodyweight and experience rather than against whoever is loudest at your gym.

Sources

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