So we are supposed to get 30 minutes of exercise 5 days a week according to the American Heart Association. That is a figure I have heard quite a few times. That totals out to 150 minutes a week. That got me to thinking about frequency of exercise, duration of exercise, and efficient use of time. My first question is if there is a proven advantage to doing exercise over 5 out of 7 days or whether fewer or even one exercise session is comparable in terms of benefits. With few exceptions (not exercising to where you break a sweat) there is a time cost associated with activities you do before and after exercise. You can optimize that by combining things, say going for a run before you shower etc and head to work, assuming you would normally shower before work, so no increased time cost over normal. There still is dressing and stretching that you would normally do so you still have a bit of time cost multiplied by number of times you engage in exercise . This is in the best case scenario. In the worst case scenario, you add in travel time to wherever you exercise, and potentially prep time to your time cost. Think going to the gym before/after work where you need to pack a bag and your work clothes and now you are doing your morning routine in a place that never seems well designed for it. So there is increased inefficiency or to word it differently there are multiple instances of time lost for each exercise session.
If this is the case, then unless there is some overriding benefit such as improved health outcomes then why incur all the extra time cost? If there is some overriding benefit, how many sessions are necessary to see that benefit – 2,3,4? Would you be even better with 20 minutes of exercise 7 days a week? I wonder when I see this kind of recommendation whether the 5 days/30 minutes is optimized based on all factors or whether it’s a more squishy “This is what we think we can reasonably ask folks to do and get some response” kind of thing.
P.S. I’m realizing that as I’m writing this that I’m going to need another post; it isn’t just about efficiency (getting the most outcomes for the amount of time invested) but in a bigger sense how a person goes about optimizing all the variables that go in to the problem. Frequency, duration, intensity, recovery, injury potential, time cost, enjoyability, and I’m probably forgetting some.