Cooling Strategies for Improving Performance and Recovery from Exercise and Reducing Fatigue in Individuals with MS

Background: Incidence of heat sensitivity is 60-80% in MS. A common complaint associated with increased heat stress (core and skin temperatures) is the early onset of fatigue. Also, the sweat response may be reduced in MS. Therefore, strategies to reduce heat production and improve heat dissipation, and consequently, reduce fatigue during activity, are needed. 

Objectives: The objective of this study was to examine the effects of Pre-Cooling (PC), Ad Lib Cooling (ALC) and Cooling During Exercise (CDE) on core and skin temperatures, and subsequent exercise performance and fatigue, as compared to No Cooling (NC) in MS patients.

Methods: Forty-five MS patients (79% female, 91% relapsing-remitting, age=50.1±8.3 yrs, EDSS=1.4±1.2, yrs since diagnosis=11.5±8.1) participated. All subjects were tested under 4 conditions (PC, ALC, CDE, and NC) in an environmental chamber set at 80⁰F and 50% humidity. The order of conditions was randomly assigned and tests were conducted once a week for 4 weeks to ensure complete recovery from fatigue between conditions. Subjects pedaled on a cycle ergometer at 60% of their individual maximal workload for as long as possible while core temperature (Tc, CorTemp ingestible pills), skin temperature (Ts, thermocouples), ECG, blood pressure and heart rate were measured continuously. Before and after the cycling in the environmental chamber, the subjects were monitored in a 70⁰F room for approximately 1 hour. Perceived physical and cognitive fatigue were assessed during exercise and recovery using a 10 cm visual analog scale.

Results: Exercise duration increased for all conditions compared to NC (24.6±9.9 min)(PC: 30.3±12.6 min, 23%; ALC: 29.2±12.9 min, 19%; CDE: 29.1±13.7 min, 18%). Perceived physical and cognitive fatigue significantly increased from before to after exercise for all conditions, with ALC having the least change. Tc increased the least amount during exercise for PC (0.58⁰C) and most for CDE (0.76⁰C) (p<.05). Tc continued to increase after the end of exercise for all conditions, ranging from 10 min (PC) to 4 min (CDE) (p<.05). After 1 hour of recovery, 56% of CDE subjects had returned to baseline Tc, while only 25% of ALC had (p<.05). Total Ts was the lowest for CDE after exercise (30.1±0.9⁰C), while ALC was the highest (31.6±0.8⁰C). After 1 hour of recovery, 80% of the CDE had returned to baseline Ts, while only 14-17% had for the other conditions. For all conditions except CDE, subjects had their highest Ts during recovery.

Conclusions: MS participants exercised longest after PC; however, the most beneficial cooling condition was CDE. During CDE, the subjects exercised longer than NC, and Tc and Ts recovered more rapidly than for any other condition. This result may assist in guiding healthcare professionals when making recommendations to their MS patients about exercising in hot environments.

This study was funded by NIDRR grant H133G050198.