A lot of wisdom (mainly MDA but also others) recommends sprinting once per week. This confuses me a little.
So why once a week sprints? What's the mechanism behind the "Less is more" approach to sprinting?
Sprint as much as you want, it really depends on your goals.
I think MDA recommends once a week because you probably don't need much more(debatable) if your goal is to maintain a basic level of health/fitness.
I don't know where your understanding of how long it takes to repair tissue comes from. It does not match mine.
Sprinting would not have been necessary for most 'hunts', not everyone in the group would have to sprint every time, and you'd struggle to eat an antelope a day. Sprinting would also have been employed as escape, but again, not every day. Our usccess on both fronts came from being smarter than that.
I expect there is also an element to which engaging in more frequent sprinting, along with your weight training, would leave you taking on intense activity most days, which would require specific fueling to maintain. Plenty of atheletes do of course, but as an all-round approach to not over-stressing the body once a week seems to be sufficient. I think you confusion mainly comes from some, erm, unexpected assumptions.
High intensity equals lower frequency. You can see this in Mark's recommendations for each type of exercise: Sprint 1x/wk, Lift Heavy Things 2-3x/wk, Walk 3-5 miles/wk. He also recommends play, which almost always would involve some sprinting (for him, Ultimate) so really you get sprints on other days, just not in a HIIT. Any more and you do risk injury in some form.
One thing I learned in my distance running days (still love the idea, just not into the sheer hours of training) is that most runners do their fast runs (tempo runs as well as HIIT and sprints) too slowly, and they do their slow runs too fast. My running times improved, along with my enjoyment, when I alternated fast days with slow days with rest days. Days off are crucial. Both in running and weight training, it's when the body grows and recovers from the "damage" intrinsic to effective training.
We can be pretty sure our ancestors didn't go running (fast or slow) for health benefits.
Hunters only sprint all the time in the movies. Most hunting is full of walking quietly, waiting, more waiting, getting lucky and then carefully following. The biggest energy expenditure is probably for keeping warm.
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