Learn about Outside Online's affiliate link policyHarvard scientists find that exercise variety is good but not too much and only certain types. And more generally, the results even hint that beyond a relatively modest amount of weekly exercise, doing more of anything doesn’t help you. I’ll take a look at three key claims: that too much exercise is bad; that certain types of exercise are uniquely bad; and that doing a variety of exercises is best. First, some background: the data in the new paper comes from two well-known cohorts: the Nurses’ Health Study and the Health Professionals Follow-Up Study. If this study had suggested that even modest amounts of exercise are bad for you, or that exercise variety shortens your life, I simply wouldn’t have believed it.