Predicting post-exertional malaise in Gulf War Illness based on acute exercise responses.

Aims: Post-exertional malaise (PEM) is poorly understood in Gulf War Illness (GWI). Exercise challenges have emerged as stimuli to study PEM; however, little attention has been paid to unique cardiorespiratory and perceptual responses during exercise. This study tested whether select exercise parameters explained variability in PEM responses.
Main Methods: Visual analog scale (0-100) versions of the Kansas questionnaire were used for daily symptom measurements one week before and one week after 30-min of cycling at 70% heart rate reserve in 43 Veterans with GWI and 31 Veteran controls (CON). Cardiopulmonary exercise testing (CPET) methods were used to measure oxygen (VO ₂ ), carbon dioxide (VCO ₂ ), ventilation (VE), heart rate, work rate, and leg muscle pain. Symptom changes and CPET parameters were compared between groups with independent samples t-tests. Linear regression (GLM) with VE/VCO ₂ , cumulative work, leg muscle pain, and self-reported physical function treated as independent variables and peak symptom response as the dependent variable tested whether exercise responses predicted PEM.
Key Findings: Compared to CON, Veterans with GWI had greater ventilatory equivalent for oxygen (VE/VO ₂ ), peak leg muscle pain, fatigue, and lower VCO ₂ , VO ₂ , power, and cumulative work during exercise (p < 0.05), and greater peak symptom responses (GWI = 38.90 ± 29.06, CON = 17.84 ± 28.26, g = 0.70, p < 0.01). The final GLM did not explain significant variance in PEM (Pooled R ²  = 0.15, Adjusted R ²  = 0.03, p = 0.34).
Significance: The PEM response was not related to the selected combination of cardiorespiratory and perceptual responses to exercise.
(Published by Elsevier Inc.)