Comparison of energetic patterns of skeletal and cardiac muscles

The shape of the basic oxygen uptake to load relationship for afterloaded contractions by in situ mammalian skeletal muscle was found to be altered significantly when the initial length of the muscles was changed from values of initial length which were less than optimal length to values of initial length which were greater than optimal length. When initial length was greater than optimal length, the relationship was like that reported for isolated amphibian muscles. When initial length was less than optimal length, the relationship was like that reported for heart muscle which is usually studied with initial length less than optimal length. If the effect of initial length is found to be the same for isolated amphibian muscles and heart muscles as it is for mammalian muscles, then the basic energetic pattern for these striated muscles will be similar.