We have demonstrated an association between higher levels of physical activity and lower levels of disease activity, depression and fatigue in youth with Multiple Sclerosis (MS). Fitness level may also influence physical activity levels as well as health outcomes in these youth. Physical fitness has not been well studied in youth with MS. Further, the relationship between fitness, physical activity, disease activity and symptoms in youth with MS is unknown.
1. To determine if there were differences in physical fitness between youth with Multiple Sclerosis and Healthy Controls (HC).
2. To examine relationships between physical fitness, physical activity level, fatigue, depression and disease activity in MS.
Youth with MS (n=19) and HC (n=21) completed a peak exercise test using a cycle ergometer protocol in order to establish cardiorespiratory-fitness (VO2peak), walking endurance was determined by a two-minute walk test, and musculoskeletal strength by grip strength using a hand dynomometer. Questionnaires determined fatigue, depression, and physical activity level. Average weekly minutes of physical activity at sedentary, light, moderate and vigorous intensities were determined by Actigraph(R) accelerometer. Tests of differences and correlational analyses were used to evaluate physical fitness.
Youth with MS demonstrated a lower average cardiorespiratory fitness of 24.7 ml/kg/min (SD = 4.4 ml/kg/min) compared with 35.2 ml/kg/min (SD = 7.7 ml/kg/min) in age and sex matched controls (T = 4.6, DF 34, P<0.001, Cohen D=1.5). The average maximum workload capacity achieved on the cycle ergometer was on average 33 watts lower in youth with MS when compared with controls (U=221, DF =33, P=0.02, Cohen D=0.5). Walking endurance was lower in youth with MS who walked an average of 644 feet compared to 670 feet in healthy controls (T = 2.6, DF=32, P = 0.02, Cohen D = 0.88); Grip Strength, physical activity level, fatigue, and depression were not different between the two groups.
Youth with MS who exhibited lower cardiorespiratory fitness had more relapses (Spearman Rho = -0.52, p =0.04) and lower grip strength scores were also associated with more disability according to the EDSS (Spearman Rho = -0.6, p=0.03). Lower cognitive fatigue was associated with increased cardiorespiratory fitness profile in youth with MS (Spearman Rho = -0.5, p = 0.03). No other relationships were observed between VO2peak, fatigue or depression in MS.
Youth with MS have lower levels of fitness, compared with HC. Higher levels of fitness were associated with lower disease activity and disability in youth with MS. Exercise interventions may be required to improve the low cardiorespiratory fitness levels found in youth with MS.