—at least for me.

Main points:
1. Anaerobic fitness elicits a cortisol stress response.
2. Fat burning happens almost exclusively aerobically.

In the past, I’ve actually been disgusted by a "not-going-hard" approach to fitness. I see ladies walking down the street cheerfully gabbing at each other. I see people who look like they are fitness walking while talking on the phone. I would run past people on trails with an elite attitude like "I’m getting more done than you are". Sidenote: I hate an idea of toxic masculinity. I say let men be who we were designed to be. But having said that, I know plenty of women who are go-getters just as much as men. I know some who are more competitive than men. But there is clearly a machismo attitude toward exercise. It’s either Go Hard or Go Home!

I’ve read the Primal Blueprint by Mark Sisson and am currently reading Primal Endurance. I’ve slowly come 180 degrees from where I was. Mark is an elite performer of triathlons and marathon events. Yet he found he could train smarter, which meant slower in an aerobic zone and for a shorter amount of time, and still keep up with elite performers. How is this possible?

When you train yourself to exercise aerobically, it means you are moving at a conversational pace. So those ladies walking down the street make sense to me now. The Maffetone formula for an aerobic maximum heart rate (MHR) is 180 minus your age. So if you are 30 years old, that’s 180 – 30 = 150. That is your maximum aerobic threshold for working out. For many, that will feel like a snail’s pace. But for others, that will feel perfect.

Mark calls an uneducated guess at our MHR the "Black Hole". You really need to use a heart rate monitor to keep your heart in check. Otherwise, you may feel comfortable just above that zone and fall into the black hole. When you get above MHR, you shift from burning fat to burning glucose. When you use up available glucose in your bloodstream, your liver releases glycogen to create more glucose. So what does this mean?

Ever hear of "skinny fat". I always wondered how it is possible to toe the line at many running races and see so many fat runners. I mean, yeah, maybe they had just started running. But there are many who I see at a lot of races who are clearly either fat or even skinny fat. The reason? Cortisol! Cortisol is a hormone that is released when you are under stress. Anaerobic activities are a form of stress. So if you are constantly redlining your heart when you run, like pushing it to where you almost have to stop, you are not aerobic, but anaerobic. And the cortisol elicits insulin to in turn shift to burning sugar. So you could end up working out every single day (Go Hard or Go Home) and burn sugar and not fat. You turn into an anti-fat-burning slob.

Yes, there are times to go hard. Short intense workouts elicit a specific response that is the subject of another blog. But Mark says to do that once every 7 to 10 days. Otherwise, spend more time in the aerobic <MHR zone. He also encourages "play". That means frisbee, biking around the block, doing some yard work, or dancing. Have fun with living an unstructured, playful life. Never be sedentary for more than 2-3 hours. Those are the keys.

Personal Revelation:
A couple weeks ago, I went on my longest run in years. It wasn’t super long compared to my days of ultramarathoning. But it felt long. I really pushed it and felt good after. I was a little sore for a few days. What amazed me was the "stressful" physiological response. Since I’ve been Intermittent Fasting (IF) and working out mostly aerobically (<MHR), I rarely feel hungry. But after this run, I was famished. I still stuck mostly to my IF, I was ravenous. The other thing? My heart was racing. Since I wear a Garmin Vivoactive 3, I can see my heart rate in real time. So for 3 days after my run, my heart rate was elevated. Yes, I was probably burning more calories. But it also meant that my body was fighting something. I wasn’t totally relaxed. I also slept very terribly for 2 nights. I monitor that too. I usually have about an 80% rating of quality sleep. I was about 35% for those two nights. Lack of sleep also ramps up cortisol. My watch also measures stress, which is related to heart rate variability (HRV). I usually am at 10-20 at rest. But I was resting at about 50 (or 50%), which means I was at moderate stress even when sitting still. So long story short, that one long run that was above my MHR upset my body for 3 days. It had a negative effect on my health and my weight loss. I was hungry, sore, and physiologically not well. I never noticed that about myself. But it made me embrace these ideas even more.