In weight training

Weight training

Weight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the weight force of gravity to oppose the force generated by muscle through concentric or eccentric contraction...

, training to failure is repeating an exercise (such as the bench press

Bench press

The bench press is an exercise of the upper body. For bodybuilding purposes, it is used to stimulate the pectorals, deltoids, and triceps. While on his or her back, the person performing the bench press lowers a weight to the level of the chest, then pushes it back up until the arm is straight...

) to the point of momentary muscular failure, i.e. the point where a repetition fails due to inadequate muscular strength.

Training to failure is, however, a controversial topic. The proponents of High Intensity Training

High intensity training

High Intensity Training is a form of strength training popularized in the 1970s by Arthur Jones, the founder of Nautilus. The training focuses on performing quality weightlifting repetitions to the point of momentary muscular failure...

 — Mike Mentzer

Mike Mentzer

Mike Mentzer was an American IFBB professional bodybuilder, businessman, and author.-Bodybuilding career:...

, Arthur Jones

Arthur Jones (inventor)

Arthur Allen Jones was the founder of Nautilus, Inc. and MedX, Inc. and the inventor of the Nautilus exercise machines, including the Nautilus pullover, which was first sold in 1970...

 and Ellington Darden — advise training to failure on every set. Other experts believe that this will lead to overtraining

Overtraining

Overtraining is a physical, behavioral, and emotional condition that occurs when the volume and intensity of an individual's exercise exceeds their recovery capacity. They cease making progress, and can even begin to lose strength and fitness...

, and suggest training to failure only on the last set of an exercise.

Heavy or light weights?

A recent study has shown that training to failure with lower loads can be more beneficial for muscle building than using higher loads. In this study, participants who trained to failure with a weight equal to 30% of their single repetition maximum ("1RM") had higher levels of muscle-building proteins 24 hours after their training session than participants who trained to failure with a weight that was 90% of their maximum.

Going beyond initial failure

When the athlete has reached initial failure (i.e. fails to perform a further repetition), the exercise can be continued by making the exercise easier (change of posture, switching to lower weight) or by recruiting help (from a spotting partner or by involving another bodypart).

This of course increases the risk of overtraining and safety issues have to be kept in mind regarding posture.

Repetition Max (RM)

Working out your Repetition Max (such as your 1RM) must be done to true failure, so this also can be considered a form of training to failure. Though 1RM is the most popular and commonly used, any number of reps can be used, for instance a 10RM or 15RM, in fact your 10RM weight will be much more useful for you in terms of training than your 1RM. Some say it can be performed with a much lower risk of joint injury (due to the lower weight), while others say a 1RM is safer because failure occurs due to absolute inability of your muscles to perform at the attempted weight rather than due to fatigue. Your 10RM would be the weight at which you can do 10 repetitions, but fail to fully perform the 11th rep.