Energy storage during stretch of active single fibres.

Abstract

One of the functions of muscles is to absorb the work done them when they are stretched while active. It has been shown by measurement of ATP hydrolysis that muscle is not a reversible energy conversion device and that work done on a muscle cannot be used to synthesise ATP (Curtin & Davies, 1973). Experiments measuring energy production as heat and work output (Hill & Howarth, 1959; Constable et al 1997) have suggested that work done on an active muscle will eventually become heat but that some of it may be stored in another form before conversion to heat. One way in which this could happen is by storage of work in elastic structures in series with the muscle crossbridges, such as tendon and the muscle filaments themselves. Work would be stored as the stress in these structures rises during a stretch and would be released as the tension falls after the stretch is over. Using measurements of the heat produced by frog single muscle fibres and of the work done on them during stretch we have observed energy storage during stretch, and the release of energy after the end of a stretch. In these preparations the tendon compliance can be kept to very low values, allowing us to investigate whether stretch in series elastic structures can account for the energy stored or whether other structures within the fibre are also capable of energy storage and release.KeywordsEnergy StorageEnergy OutputIsometric ContractionElastic StructureForce EnhancementThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.