Fitness and its association with fatigue in persons with multiple sclerosis.

This study compared physical fitness components between fatigued and non-fatigued persons with MS and examined those components as correlates of fatigue. Sixty-two ambulatory persons with MS completed the Modified Fatigue Impact Scale (MFIS) and underwent assessments of cardiorespiratory capacity, lower extremity muscle strength (i.e., peak torque and asymmetry), body composition, and static balance over two different sessions 7 days apart. Participants were allocated into fatigue groups based on MFIS scores (non-fatigued group (i.e., MFIS ≤38), n = 26; and fatigued group (MFIS >38), n = 36). The fatigued group had significantly (P < 0.05) lower cardiorespiratory capacity (VO2peak ) and muscular strength (i.e., knee flexion peak torque) than the non-fatigued group. VO2peak and knee extension peak torque were the two physical fitness components significantly correlated with fatigue scores in the fatigued group (P < 0.05), and follow-up stepwise linear regression revealed that VO2peak was a significant predictor of fatigue scores (R2  = 0.13). Discriminant function analysis further identified VO2peak as a significant (P < 0.05) correlate of fatigue status. This model explained 21% of variance in group status (i.e., fatigued vs non-fatigued) and correctly classified approximately 76% of cases into fatigue status groups. The improvement of cardiorespiratory capacity should be considered in rehabilitation programs for persons with MS, especially those presenting with elevated fatigue.