Aerobic capacity explains physical functioning and participation in patients with multiple sclerosis-related fatigue

OBJECTIVE: To investigate whether aerobic capacity explains the level of self-reported physical activity, physical functioning, and participation and autonomy in daily living in persons with multiple sclerosis-related fatigue.

DESIGN: A cross-sectional study.

PATIENTS: Sixty-two participants with multiple sclerosis-related fatigue.

METHODS: Aerobic capacity was measured with a leg ergometer and was expressed as maximal oxygen uptake (VO2max, in ml/kg/min). Physical activity was measured with the Physical Activity Scale for Individuals with Physical Disabilities (PASIPD), physical functioning with the Short Form 36 - physical functioning (SF36-pf), and participation and autonomy in daily living with the Impact on Participation and Autonomy questionnaire (IPA). Multiple regression analyses were performed, adjusted for potential confounders (gender, age, body mass index, educational level, and employment status).

RESULTS: Mean maximal oxygen uptake (VO2max) was 23.9 ml/kg/min (standard deviation (SD) 6.3 ml/kg/min). There was no significant relationship between VO2max and physical activity (PASIPD): β = 0.320, 95% confidence interval (95% CI) = -0.109 to 0.749, R2 = 10.8%. Higher VO2max correlated with better physical functioning (SF36-pf): β = 1.527, 95% CI = 0.820-2.234, R2 = 25.9%, and was significantly related to IPA domains "autonomy indoors" (β = -0.043, 95% CI = -0.067 to -0.020, R2 = 20.6%), "autonomy outdoors" (β = -0.037, 95% CI = -0.062 to -0.012, R2 = 18.2%) and "social life and relationships" (β=-0.033, 95% CI = -0.060 to -0.007, R2 = 21.3%).

CONCLUSION: Maximum aerobic capacity was severely reduced in persons with multiple sclerosis-related fatigue. This partly explains the limited physical functioning and restrictions in participation and autonomy indoors, outdoors and in social life and relationships in these persons.