Extensive exercise is not harmful in amyotrophic lateral sclerosis (ALS)
Abstract written by Anne Kiraly
Present hypotheses state that excitotoxicity, oxidative stress, and increased calcium loads cause degeneration of vulnerable motor neurons and that extensive exercise may accelerate these factors. The purpose of this study was to test these hypotheses and determine the effects of long-term, vigorous exercise on the onset and progression of amyotrophic lateral sclerosis (ALS) in mice.
The mice used in this study were bred to express the mutant human form of the Cu/Zn superoxide dismutase-1 (SOD-1), a model of ALS.
Thirty-seven mice were divided into three groups: active, sedentary, and control. Each mouse was confined to its own cage. After becoming familiar with the motor-driven running wheels, the active group had to run a total of 400 minutes per day on the wheels, in intervals of 10 minutes. The wheels were set at a predetermined speed (3.4/min), but all mice voluntarily exceeded this speed on a regular basis, until the disease progressed past a certain point. The sedentary group was also forced onto running wheels, but the speed was kept at slow motion (0.1m/min). Authors monitored the course of disease in the mice by taking measurements of grip strength (GS), stride length (SL), and a modified tight rope test (TRT) every 3 days during the study. GS was measured using a GS meter; SL was measured by having the mice walk over an inkpad and then onto white paper and then measuring the distance between the footsteps; performance on the TRT was scored between 0 and 11. Mice were killed after the disease had progressed past a certain point, as measured by the GS. Statistical analyses of the data were performed using change-point analysis and ANOVA.
The results indicated that there were no significant differences in the course of disease between the groups. In all groups, SL reached a maximum at an age of 100 days, GS declined after about 91 days, and performance on the TRT declined after 15 weeks. Onset of disease in the active group was not significantly different from the other groups. Survival times of the mice in the active group exceeded those of the sedentary group by 6.5 days and the control group by 4.6 days, but these differences were not statistically significant.
The authors state that their results support that prolonged, vigorous exercise “does not promote the onset or progression of motor neuron degeneration in SOD-1-mediated ALS.” They mention, however, that exercise cannot be ruled out yet as a risk factor because of the number of athletes or previous athletes who have been stricken with ALS. They discuss research that has already been conducted and the amount of work that still needs to be done. However, it is difficult to conduct this research on a disease that progresses this quickly.