Will exercise help spinal stenosis and how?

Perhaps. Exercise that strengthens the abdominal (tummy) muscles could reduce the curve of the low back (lordosis). This could enlarge the nerve channels slightly. This might suffice in mild cases of stenosis. Aerobic exercise in a flexed position (such as cycling) could improve overall fitness and that might improve symptoms. Exercise may be most beneficial in people with milder, less disabling symptoms.
Not really. Exercise is in general is good, but it really does not do much for the condition of spinal stenosis. Somewhat similar in thought process to exercise not really doing a lot for a severely arthritic knee.
Short answer, yes! Here's an excellent article on spinal stenosis which mentions the benefits of exercise. Http://www. Rheumatology. Org/practice/clinical/patients/diseases_and_conditions/stenosis. Asp you will find that walking uphill or doing anything in a forward bent position will feel better than anything done with your back arched backwards, because it increases the space between bones around your spine.