Effect of potentiation on the catchlike property of human skeletal muscles.

The catchlike property of skeletal muscle is the force enhancement produced when a brief, high-frequency burst of pulses (two to four pulses) is added to a subtetanic train of pulses. Stimulation trains that take advantage of the catchlike property have been shown to produce greater forces than trains commonly used during clinical application of functional electrical stimulation (FES). We recently showed, however, that there was no force enhancement observed with the catchlike property when muscles were nonfatigued and highly potentiated. Thus, understanding the relationship between the force augmentations produced by the catchlike property and potentiation may provide insight into the physiological conditions that best take advantage of the catchlike property. The goal of this study was to explore quantitatively the effect of potentiation on the catchlike property of the muscle. Isometric data were collected from human quadriceps femoris muscles. A negative linear relationship between the force augmentation produced by the catchlike property and the amount of potentiation was observed. These data showed that for nonfatigued muscles, the catchlike property would be most beneficial at the onset of activation, when muscles are the least potentiated. These results should help to guide clinicians to design stimulation protocols that optimize performance during FES.