Residual Force Enhancement following muscle lengthening has been shown in various muscle preparations but the mechanism behind it has not been fully understood. There is the possibility that its properties are evident at the single molecule level.

The purpose of this thesis was to investigate force enhancement at the single molecule level. If by stretching a single attached cross-bridge, with the use of an optical laser trap, the length of attachment would be increased and therefore produce more force.

The length of attachment, of a single bound myosin molecule to an actin filament after a stretch was found to be the same as when the cross-bridge was shortened. It was concluded that at this time residual force enhancement cannot be explained by a stretch induced increase in the dwell time of an attached cross-bridge. However, insight into how a myosin II molecule behaves in an optical laser trap, under different forces was made.