Heat Acclimation of an Individual with a Spinal Cord Injury: A Case Report

Abstract

Individuals with spinal cord injury (SCI) have impaired temperature regulation because of disrupted autonomic neural pathways. Additionally, thermal afferent feedback from sensory nerves is decreased, thus reducing the stimulus for an appropriate thermoregulatory effector response from areas of sensate skin. These events lead to increased cardiovascular and thermoregulatory strain during physical activity. Heat acclimation reduces cardiovascular and thermal strain during heat exposure in healthy able-bodied individuals, but responses in individuals with SCI are unknown. PURPOSE: To test the hypothesis that a 7-day heat acclimation regimen attenuates cardiovascular and thermal strain during exercise-heat stress of an individual with an American Spinal Injury Association A "complete" spinal cord lesion at the eighth thoracic vertebra. METHODS: A 34-year-old man with an SCI lesion at T8 performed arm-crank ergometry exercise at 40% of mode-specific peak oxygen uptake in a climatic chamber set to 40 °C and 30% relative humidity for 60 min (two 30-min sessions separated by 5 min of rest) each day for 7 d (all days were successive except for 1 day between acclimation days 4 and 5). RESULTS: Between day 1 and day 7 of heat acclimation, final heart rate (164 vs. 147 beats·min-1) and the rise in core temperature (Tc) from baseline to the final minute of exercise (1.08 vs. 0.60 °C) decreased. Furthermore, for a given increase in T during exercise, the increase in sweat rate from the chest was enhanced from day 1 to day 7 (0.088 vs. 0.812 mg·cm−2·min−1/°C). Perceptual responses (rating of perceived exertion and thermal sensation) also were lower by the end of acclimation. CONCLUSION: Heat acclimation was effective in improving thermal tolerance in this individual with paraplegia, thereby increasing comfort and safety during exercise and situations involving elevated ambient temperature. Supported by NIH Grants HL61388 and HL84072.