Heating had no effect upon either force decline or slowing of relaxation during fatiguing contractions. The force-frequency relationship of the paralysed quadriceps muscle was shifted to the right after the muscle was heated. Despite this shift, however, the relationship still resembled that in muscles of non-paralysed individuals, probably due to the unexplained high twitch forces. These results indicate that reduced muscle temperature in spinal-cord-injured individuals may lead to an underestimation of the changes in contractile properties in terms of relaxation rate or the degree of fusion with low-frequency stimulation. In addition, the force-frequency relationship of paralysed muscles does not accurately reflect the magnitude of these changes, even when the muscle is heated, and should therefore be treated with caution.
HL Gerrits collected this research data on spinal cord injured people as part of her PhD supervised by Professor Anthony Sargeant. One problem encountered in trying to assess any training induced changes in the contractile properties of the paralysed muscles using electrical stimulation is that the muscles can be colder than normal as a consequence of circulatory changes.
Influence of muscle temperature on the contractile properties of the quadriceps muscle in humans with spinal cord injury
Clin Sci (Lond). 2000 Jan;98(1):31-8