Muscular Failure

Muscular failure in resistance training refers to the point during a set when a person can no longer complete another repetition against the given resistance despite attempting to do so. A more precise term is momentary muscular failure, commonly defined as the inability to complete the concentric portion of a repetition despite maximal effort. Failure is therefore specific to the exercise, load, technique, and conditions of the set rather than meaning that the muscle has completely lost its ability to produce force .¹

As repetitions accumulate, fatigue reduces the force-producing capacity available for the task. When the force required to complete the movement exceeds the force that can be produced under those conditions, another complete repetition becomes impossible. How many repetitions can be performed before this point depends on factors such as load, exercise selection, accumulated fatigue, and the individual performing the exercise .^1,2

Terminology surrounding muscular failure is not fully standardized. Momentary muscular failure specifically involves an unsuccessful attempt to complete another repetition despite maximal effort. Volitional failure can instead refer to voluntarily ending a set when the person judges that another repetition cannot be completed. Proximity to failure is commonly expressed as repetitions in reserve (RIR), representing the estimated number of additional repetitions that could have been completed .¹

Training to muscular failure can produce a high level of effort and fatigue, but reaching failure on every set is not required for improvements in muscular strength or hypertrophy. Meta-analytic evidence indicates that resistance training stopped before failure can produce similar adaptations under many training conditions .²