Impact of high intensity exercise on endurance capacity, muscle strength and glucose tolerance in multiple sclerosis

I. Wens, K. Verboven, D. Hansen, B. Op't Eijnde (Diepenbeek, BE)

Background and aims: Today it is clear that low to moderate intensity physical activity improves physical capacity, muscle strength and overall functioning in Multiple Sclerosis (MS)(Motl et al., 2005). However, similar to other populations, high intensity exercise may improve training outcome even more (Dalgas et al., 2008). Furthermore, MS often leads to a more inactive lifestyle, increasing the risk to develop secondary health problems, such as impaired glucose tolerance (Wens et al., submitted). In other populations, physical activity is used to treat and/or prevent this (Hawley et al., 2008). Therefore, the present study investigated the effect of high intensity interval training (HIIT) vs. intense combined (strength and endurance) exercise (EX) on endurance capacity, muscle strength and glucose tolerance in MS.

Methods: At baseline and after 12 weeks of HIIT or EX, maximal endurance capacity (incremental cycle ergometry, Oxycon©), isometric leg muscle strength (flexion and extension, knee at 45° and 90°, Biodex©) and glucose tolerance (1 gr glucose/kg body weight, Analox GM7 Micro-stat©) were assessed in 13 sedentary MS controls (CON), 12 HIIT and 11 EX MS patients.

Results: At baseline, groups did not differ. In HIIT, peak work load (+18%), test duration (+20%) and VO2max (+17%) significantly improved (p<0.05) after 12 weeks of exercise. In CON and EX these parameters remained stable. Furthermore, 12 weeks of exercise was able to improve muscle strength of the weakest leg of HIIT (+27 to +55%, p<0.05), whereas the improvements of EX (+2 to +13%, p>0.05) did not reach statistical significance. Muscle strength of CON remained stable or tended to decrease (-1 to -12%). After 12 weeks, total area under the glucose curve of HIIT (-9.2%) and EX (-10%) significantly decreased (p<0.05), whereas it remained stable in CON. Serum insulin concentrations will be measured in August 2013 and presented at ECTRIMS 2013. Finally, no exacerbations were reported during the study.

Conclusion: HIIT exercise seemed to be more effective to improve endurance capacity, muscle strength and glucose tolerance in MS, since intense EX only improved glucose tolerance and tended to improve muscle strength. Furthermore, MS patients tolerated HITT well. Therefore, under the conditions of the present study, we can conclude that HIIT exercise could be a useful tool in MS rehabilitation, improving primary and secondary symptoms in MS.