Extensive exercise is not harmful in amyotrophic lateral sclerosis

Abstract

Whether physical activity increases risk or promotes progression of motor neurone degeneration in amyotrophic lateral sclerosis (ALS) is still debated. Current pathophysiological hypotheses include excitotoxicity, oxidative stress and increased calcium loads as causes of selective degeneration of vulnerable motor neurones. Vigorous exercise might amplify these factors by increasing firing rates at motor neurones. To test this hypothesis, we constrained a transgenic mouse model of ALS overexpressing the mutant human form of the Cu/Zn superoxide dismutase-1 (SOD-1) to a lifetime exercise on motor-driven running wheels for 10 h daily (active group, n = 12). Onset and progression of disease were assessed by grip strength, stride length and tight rope test. Data were compared with SOD-1 mice placed in running wheels set to slow speed (sedentary group, n = 13). Untreated SOD-1 mice were an additional control group (n = 12). We found no differences in disease onset, which was determined by a change-point analysis using an iterative fitting of segmented linear regression models, or in disease progression. However, the running group showed a non-significant 6-day improvement in survival (133.7 +/- 3.2 days) compared with the sedentary group (127.2 +/- 3.2 days) and a 4-day improvement compared with the control group (129.1 +/- 2.5 days). We demonstrate that a lifetime of vigorous exercise does not promote onset or progression of motor degeneration in SOD-1-mediated ALS. Moreover, the results suggest that the level of excitatory input and calcium turnover at motor neurones, both of which should be increased by running activity, do not interfere with the pathophysiology of SOD-1-mediated ALS.