Complexity and pitfalls in maximal exercise testing for persons with multiple sclerosis

Valid measurements of cardiorespiratory fitness in persons with multiple sclerosis (pwMS) are essential during inpatient rehabilitation for a precise evaluation of the current health status, for defining appropriate exercise intensities, and for evaluation of exercise intervention studies. We aim (i) to examine the proportion of pwMS who attain the American College of Sports Medicine (ACSM) criteria for maximal effort during graded cardiopulmonary exercise testing (CPET) and (ii) to provide insight into participant characteristics that limit maximal exercise performance.

This cross-sectional study comprises a retrospective examination of ACSM criteria for maximal effort during graded CPET of n = 380 inpatient pwMS (mean age = 48 ± 11 years, 66% female). Chi-squared or Fisher's exact tests were conducted to compare differences in the distribution of criteria achieved. Participants' characteristics were examined as potential predictors using binary logistic regression.

Only 60% of the overall sample attained a respiratory exchange ratio ≥ 1.10. With regard to the definition applied, only 24% or 40% of the participants achieved an oxygen consumption plateau, and 17% or 50% attained the heart rate criterion. Forty-six percent met at least two of three criteria. Disability status, gender, disease course, and body mass index were associated with the attainment of maximal effort.

Our findings suggest that a relevant proportion of inpatient pwMS do not attain common criteria utilized to verify maximal oxygen consumption. Identified predictors for criteria attainment can be used to create models to predict cardiorespiratory fitness and to optimize CPET protocols in restrictive groups of pwMS.