Does ‘training to failure’ build better muscle strength?

It is easy to assume that harder training always produces better results. In resistance training, which includes lifting weights or using resistance machines, taking every set to the point where you cannot complete another repetition may create more fatigue without producing better results.A repetition, or rep, is one complete movement of an exercise. A set is a group of repetitions performed without a long rest.Training to failure means continuing a set until you cannot complete another full repetition with acceptable technique, despite making your best effort. This is sometimes called momentary muscular failure.An alternative is to stop while you could still perform one or more repetitions. This is described as repetitions in reserve, or RIR. If you could complete 10 repetitions but stop after eight, you have two repetitions in reserve, usually written as 2 RIR.Why might training close to failure help?Muscles are made up of individual cells called muscle fibres. These fibres are broadly classified as type 1 or type 2 fibres and are controlled by the nervous system. The type 2 fibres produce more force and can grow more than type 1 fibres.A light load is generally one that you could lift for more than 15 repetitions, whereas a heavy load limits you to completing fewer than 10 repetitions. When lifting a light load, the type 1 fibres are active. As the set approaches failure, the nervous system activates type 2 fibres to keep the weight moving.Lifting a heavy weight activates type 2 muscle fibres from the beginning of the set. With a light weight, type 2 fibres only become activated as the type 1 fibres fatigue later in the set. Light-weight sets therefore need to be completed reasonably close to failure if the aim is muscle growth.The final possible repetition does not appear to provide a special muscle-building effect. Research suggests that a hard set ending shortly before failure can stimulate muscle growth while causing less fatigue.What are the drawbacks?Taking a set to failure produces more immediate fatigue than stopping earlier. A systematic review and meta-analysis, which combines the findings of several studies, found that failure training caused larger reductions in strength, movement speed and power immediately after exercise. It also produced greater feelings of effort and more signs of temporary muscle disruption.