Glossary · Fitness
1RM (One-Repetition Maximum)
The 1RM is the heaviest load that can be lifted exactly once with clean technique in a given exercise.
Why it matters
1RM is an exercise- and day-specific reference for maximal strength. Percentages of it can structure training but are not universal prescriptions for every set.
A 1RM can be tested directly or estimated from multi-repetition sets. Equations such as Epley or Brzycki provide approximations whose error varies by exercise, repetition count and person.
There is no single percentage of 1RM that is automatically optimal for hypertrophy or strength. Goal, repetitions, effort and exercise determine useful loading.
Direct maximal attempts require appropriate technique, environment and safety measures. An estimate avoids the test but does not turn the result into a measurement.