In weight training, training to failure is repeating an exercise to the point of momentary muscular failure, i.e. the point where the neuromuscular system can no longer produce adequate force to overcome a specific workload.
[1][2] Two systematic reviews published in 2021 found no benefit to training to failure on hypertrophy, while one of the reviews found some evidence that not-to-failure training is superior for strength.
Determining a repetition maximum must be done to true failure – by definition, it represents the weight and repetition count at which the person reaches failure, and can no longer lift.
Training past form failure can cause joint and muscle injury and should never be attempted.
Beginners should train to pre-failure or tempo failure, while focusing on maintaining proper form.