I agree that humans likely did not evolve performing excessive cardio (e.g., an hour+ of elliptical every day), but we also did not evolve to sit in a chair 10+ hours per day.
I understand that interval training may best approximate the kind of activity a HG did, but what about approximating the shear volume of activity? If we are sedentary for most of the day, could you argue that excessive cardio is an adaptation that allows us to get closer to the total daily volume of physical activity performed by a HG? Or maybe my assumption of higher activity levels is wrong? Do we have estimates of average daily calories consumption/expenditure for HG?
What if we our appetites, satiety, etc. evolved under conditions where there was a high volume of daily activity? Could excessive cardio help approximate that and possibly make it even easier to reach equilibrium at a healthy weight? Maybe our bodies can more naturally regulate themselves at a 3,000 calorie/day equilibrium rather than a 2,500 calorie/day equilibrium (for example)? Could the benefits of that potentially outweigh the cost?
I understand that burning extra calories should induce us to eat more and am not disputing that, but I do not think it's completely black and white and likely the relationship is not exactly 1-to-1. I.e., for every 1 extra calorie burned, I do not think it induces us to consume exactly 1 extra calorie. It is one of many factors, and maybe the grey area is important?
As I'm typing this, I realize you could just say why not do more interval training each day. Maybe that's a fair point, but perhaps something like an elliptical machine packs more bang per buck - i.e., more activity (calories) per hour of time. And, I think elliptical is easier to sustain regularly for longer periods (at least for some of us) because it can be mindless and allow you watch TV or read or think while doing it. I know - some of the exact reasons it's criticized.
Also, I know there are lots of ways to add in activity throughout our day: bike/walk to work, standing desks, treadmill desks, etc. I'm sure there are existing posts on that. That's not what I'm looking for.
Anyway, could we consider "excessive" cardio an adaptation which enables us to approximate the higher daily activity levels of a HG, even though we are forced to be sedentary for much of the day?
Great question. This idea of how cardio fits into my personal paleo framework is a big one right now. I've eaten a predominantly autoimmune-focused paleo diet for the past few years and have shifted my activity away from "chronic cardio" and towards strength and HIIT-based work. I was an endurance cyclist for many years and focused very little (like...nothing) on strength training. I dropped cycling almost completely about two years ago and focused (first) on rehabbing injuries and fixing strength imbalances, then started weight training - all compound barbell movements inspired by Starting Strength. The results have been great. I've put on about 10 lbs in muscle (and a little in fat), and am stronger at 41 than I ever was as a 21-year old rugby player.
However...I just recently completed a full cardiorespiratory/metabolic fitness assessment. VO2 max, lactate threshold, RMR, the works. I went in thinking I would ace the test and get back under the barbell posthaste. My trainer (who knows I haven't biked in a couple of years) looked at me and said "You've failed to meet the low standards you've set for yourself." Turns out my CV conditioning is now in the low Fair range (just above Shitty). Now I guess you could argue whether or not those tests are a good measure of fitness and health, but I can see on a very clear graph how poorly my cardiac and metabolic systems respond to increased workload. I basically go from resting to anaerobic in seconds at relatively low effort.
What I've concluded from this is: while the weight and HIIT have been amazing, there is a whole range of performance that I've ignored. To get my little mitochondria burning better, I've added back low to mid-intensity cardio in the form of 30 minute trail runs and the occasional 2-3 hour bike ride. I'm still in the gym working hard every week but have replaced one session and a couple of rest days with cardio work. I feel good and haven't noticed any change in hunger, sleep, stress, etc, but it's still early days, so we'll see how it goes.
I don't know that "excessive" cardio is a healthy adaptation to a sedentary lifestyle. If research suggests that it is the sedentary part that's the problem, then it's not clear to me why cortisol-raising cardio a few times a week would counteract that.
My money is still on Mark Sisson's fitness framework: lots of low and slow, some sprinting, some resistance work.
A couple of comments, related to physical condition of adult male Neolithic skeletons reported by Hodder:
-Evidence of a lot of arm/shoulder use. I take this to mean that humans were their own dray horses before ca 10,000 BC.
-Evidence of considerable time spent squatting...which makes sense before chairs, though maybe not 10 hours a day.
I think you make an excellent point.
Ideally, we'd spend all day walking around performing physical tasks and occasionally sprinting or the equivalent of lifting weights, but if you're absolutely desk-bound then brief (<=20 min), moderate (<70% MHR) aerobic exercise would seem to be the next best thing.
I don't think it's necessary to avoid any type of exercise specifically. Overtraining is the enemy, and you can overtrain with sprints, weights, or anything else.