Perceptual And Metabolic Responses To Exercise In Chronic Multisymptom Illness

Post-exertional malaise (PEM) is a general worsening of symptoms following physical or mental exertion and a characteristic of chronic multisymptom illnesses (CMI) including Gulf War Illness (GWI), Chronic Fatigue Syndrome (CFS), and Long Covid. Cardiopulmonary exercise testing (CPET) has been used to elicit PEM and the existing data suggest an altered, pro-inflammatory, albeit heterogeneous, peripheral response to exercise in CMI that is often unrelated to symptoms. The pathophysiological antecedents of PEM are still unclear; understanding the perceptual and cardiopulmonary responses during exercise may provide greater insight into the post-exertional consequences for those with CMI. The present data were collected as part of a larger protocol testing the neuroinflammatory response to exercise in CMI with the goal of furthering our understanding of the mechanisms underlying PEM. Purpose: To compare the perceptual and cardiopulmonary responses to a standardized submaximal exercise test in CMI. Methods: 14 individuals with CMI (6 Long COVID, 6 CFS, and 2 GWI) and 14 age- and sex-matched controls (CON) completed a 30-min, submaximal (70% heart rate reserve; HRR) cycle ergometer test. Continuous CPET data were collected during (time points 1-6, 5-min averages) and following the test during cool down (time point 7, 1-min average). Ratings of leg muscle pain intensity and overall fatigue were also collected every 5 min during the test and once during cool down. A doubly multivariate MANOVA was calculated with time (1-7) and group (CMI vs CON) as main effects and with fatigue, tidal volume, respiratory rate, work rate, and VE/VCO2 as the multivariate outcomes. Results: The groups did not differ on age (CMI = 40.7, CON = 39.6), sex (65% female for both), BMI (CMI = 26.0, CON = 27.8) or percent time spent in their prescribed HRR zone (CMI = 83.5, CON = 90.1). For the exercise test, there was a significant effect for time (p > 0.001), but not for group (p = 0.803) or group by time interaction (p = 0.431). Conclusion: Our results suggest CMI and CON have a similar response to a standardized bout of submaximal exercise. Further analysis is needed to identify how these factors are related to post-exercise perceptual (i.e., PEM) and physiological (i.e., neuroinflammation) responses.Funded by the University of Wisconsin-Madison. Supported by: University of Wisconsin – Madison