There are two types of muscle fibre:
Slow-twitch fibres contract slowly and release energy gradually as required by the body during steady-state activity such as jogging, cycling and endurance swimming. These fibres are efficient in using oxygen to generate energy (ATP), making them resistant to fatigue but unable to produce the power of fast-twitch fibres. When the body is engaged in endurance-type activity, slow-twitch fibres are preferentially recruited for the movement because they are more efficient in meeting the immediate demands of the working muscles.
Fast-twitch fibres contract quickly and release energy rapidly however, they fatigue rapidly due to anaerobic metabolism providing the energy. The body preferentially recruits fast-twitch fibres to perform explosive type activities such as weight-lifting, field athletics and sprint track athletics. Two types of fast-twitch fibres can be explored further through the link at the bottom of this page.
The individual’s ratio of fast-twitch to slow-twitch muscle fibre is genetically determined, making them more suited to certain sports or activities. The ratio of both types of muscle fibre varies in each individual and each muscle. In summary:
Sport specific training will assist in appropriate development and adaptation of each type of muscle fibre. Fast-twitch muscle fibres benefit most by anaerobic training, such as sprint or interval training and resistance training. Slow-twitch muscle fibres benefit most from endurance type activities that engage the aerobic system, such as running, cycling and swimming.
The adaptations that can occur in response to training are shown in the table below.
|Aerobic training - in slow-twitch fibres||Anaerobic training - in fast-twitch fibres|
For more information on muscle fibre types click on the following link: