Muscle failure is a term used in weight training to describe the point at which the neuromuscular system can no longer produce adequate force to overcome a specific workload. It is the point where a muscle can no longer contract concentrically. There are two types of failure - muscular failure and mechanical failure. Muscular failure is when the neuromuscular system can no longer produce adequate force for a muscle or muscle group to contract concentrically, while mechanical failure is when you can no longer perform the movement by executing safe and correct form through a full range of motion.

Training to failure involves repeating an exercise to the point of momentary muscular failure. This means that you continue to perform an exercise, such as the bench press, until you can no longer produce adequate force to overcome the workload. 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.

Research on the benefits of training to failure is mixed. 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. However, a review of several studies found that training to failure uses more motor units and can lead to an increase in muscle and strength gains over time.

The current consensus is that you need to be within ~2-5 reps of muscular failure to provide an adequate stimulus for muscle growth. This implies that you don’t need to take every set of every exercise to the absolute limits. There may be an appropriate time and place to hit muscular failure, for example during 1RM testing, AMRAP testing, or during the last set of your isolation exercises. However, to protect yourself and avoid accumulating injuries, it’s recommended that you avoid training to failure regularly.