Temperature responses to electrically induced cycling in spinal cord injured persons

The purpose of the study was to investigate the core temperature responses to the induction of electrical exercise and to clarify whether an increase in temperature could be responsible for some of the observed reactions to acute and repeated exposure to electrical muscle stimulation. The paralyzed thigh and gluteal muscles were stimulated electrically with surface electrodes in seven persons with transection of the spinal cord. By this means, they were able to pedal a lower extremity ergometer at 50 revolutions per minute for 30 min. Skin surface, esophageal (Tes), rectal (Tre), and muscle temperature in m. quadriceps were measured with thermocouples. The average rate of oxygen consumption was 0.91 +/- 0.16 L.min-1, and the heart rate after 20 min was 123 +/- 9 bpm during the electrically induced exercise. The involuntary, induced exercise led to increases in core temperature, whereas skin surface temperature was the same before and after exercise. Average Tes and Tre both rose 0.7 degrees C from, respectively, 36.6 +/- 0.2 and 36.9 +/- 0.1 degrees C, and muscle temperature increased even more: 2.9 degrees C from 33.9 +/- 0.3 degrees C. It is suggested that these increased temperatures may act as stimuli, directly or, through resulting release of humoral factors, and elicit the changes in heart rate, as well as the previously observed adaptive changes after electrically induced exercise, e.g., in muscle fiber size, and capillarization.