Here is a link to a research paper published in 2010: Aerobic Fitness & MS
The key message is that: “Cardiorespiratory fitness, a physiological surrogate of physical activity is increasingly being recognized as having a neuroprotective effect on neurological disorders (White & Castellano, 2008). Both initial non-human animal research (Le Page et al., 1994, 1996) and cross-sectional human research (Prakash et al, 2007) provide promising evidence for the possible role of fitness in improving functioning in those with MS.”
According to White & Castellano (2008) the neuroprotective effect of physical activity derives from changes in neuroactive proteins. They also say that doing physical activity may help improve mood swings, learning and memory.
Personally, I do feel much better if I move. Although I love the relaxing, restoring yoga sequence, I find that more dynamic sequences – or running- have more impact on my cognitive abilities. I feel “sharper” after an active workout. And the more I do, the more I can do (ie the less tired I am).
Obviously we are all different. We all have our own limits but I think it is good to keep in mind that we should work on our fitness too.