Saying that exercise keeps the mind sharp normalizes not exercising. I prefer to think of exercise as normal and sitting around as the mind-dulling deviation.

Saying that exercise keeps the mind sharp normalizes not exercising. I prefer to think of exercise as normal and sitting around as the mind-dulling deviation. I would say: Not exercising can dull the mind. or A sedentary lifestyle instead of getting your heart pumping can dull the mind.