Exercise is the number one thing I can control for my disease management. I have found that most of my symptoms respond on a day to day timescale from sleep, stress and exercise. I can't always control the first two - sometimes my feet cramps prevent me from sleeping and stress from work/life/people can happen when you least expect it. But exercise is the one thing I can control independent of other external factors. There is a lot of interesting research about increasing brain volume with exercise and also positive effects of exercise on your immune system. I certainly have noted a vast decrease in my symptoms when I am at least working out fairly strenuously 4x per week for a minimum of 15 min. The key point here is I've noticed it has to be cardiovascular exercise. I do not see the same benefits from yoga or even strength training though they are beneficial to your health for other reasons and perhaps some people with MS will find those more beneficial. And recent research suggestions only 1 minute of intense exercise spread over 10 min of mild effort has the same benefit as a 45 min of moderate exercise. Another study showed that even walking on a treadmill increased cognition in people with MS. And this study showed increased quality of sleep for MSers, particularly with low-intensity exercise. Exercise is known to have a cascade effect in your brain and hormones. For example it increases neurotrophins (e.g. BDNF, IGF1, VEGF, etc), synaptogenesis, angiogenesis, production of neurotransmitters, telomere length, and increases genes associated with plasticity and mitochondrial function and reduces genes associated with oxidative stress. Exercise also reduces the beta amyloid protein implicated in Alzheimer's and enhances learning and memory. And exercise reduces cancerous tumor growth. In research on persons with MS, those who maintained exercise regimes had 26% better physical health, 13% better mental health, 39% more energy, 18% better social function, and 16% better overall quality of life. Research from Parkinson's has also shown that in particular, forced exercise, ie) going about 30% faster than what you would ordinarily prefer, has increased brain volume. In part this research as led to the peddling for Parkinson's programs which emphasize tandem cycling with a healthy partner to keep the repetitions per minute higher than what they might be if people were left on their own. Some other interesting findings have found out that while cognitive training has specific beneficial outcomes (ie if you practice your memory then only your memory will improve) exercise benefits all cognitive processes. Prakash et al., 2009 showed that in MS patients, exercise was beneficial to gray matter volume and white matter integrity. Forming an exercise habit can be difficult. Often people start too hard, maybe even injuring themselves or pulling a muscle and then the goal to start exercising quickly fades. Research has shown it is better to form a habit by first starting with a ridiculously easy goal. Say going for a walk or run only 5 min every day. Something that is trivial for you in both time and exertion. Do that for several weeks before increasing to 10 min and then 15. The idea is to form the habit first before increasing the intensity. It's easier to change only one thing in your life at a time. Once it's a habit then you can increase the intensity and start noticing the benefits. So go out and exercise! Be encouraged! Here is an overview on exercise and MS from the St. Barts MS research center.