Setting Your Biological Clocks With Exercise

This is a review of an article I was entertained by this morning. Some of it is something that I have been thinking about for a long time but had never heard or seen it before today.

Please hang with me as I unpack this important information. It is a little heady but there is gold in this. Get through the first part with me and then the ideas get better as we continue.


I’m going to review this article and then add my interpretations and opinions. It was published in
“Nature”: Reviews in Endocrinology
Review Article | Published: 17 January 2019
Circadian rhythms and exercise — re-setting the clock in metabolic disease
Brendan M. Gabriel & Juleen R. Zierath

“Circadian rhythms and exercise — re-setting the clock in metabolic disease”


“Perturbed diurnal rhythms are becoming increasingly evident as deleterious events in the pathology of metabolic diseases. Exercise is well characterized as a crucial intervention in the prevention and treatment of individuals with metabolic diseases. Little is known, however, regarding optimizing the timing of exercise bouts in order to maximize their health benefits.

“Furthermore, exercise is a potent modulator of skeletal muscle metabolism, and it is clear that skeletal muscle has a strong circadian profile. In humans, mitochondrial function peaks in the late afternoon, and the circadian clock might be inherently impaired in myotubes from patients with metabolic disease. Timing exercise bouts to coordinate with an individual’s circadian rhythms might be an efficacious strategy to optimize the health benefits of exercise. The role of exercise as a zeitgeber (A zeitgeber is any external or environmental cue that entrains or synchronizes an organism's biological rhythms to the Earth's 24-hour light/dark cycle and 12-month cycle) can also be used as a tool in combating metabolic disease. Shift work is known to induce acute insulin resistance, and appropriately timed exercise might improve health markers in shift workers who are at risk of metabolic disease. In this Review, we discuss the literature regarding diurnal skeletal muscle metabolism and the interaction with exercise bouts at different times of the day to combat metabolic disease.”

Key points:

• Skeletal muscle has an extensive network of clock-controlled genes, and dysregulation of its molecular clock can lead to deleterious metabolic consequences.

• Physical strength and skeletal muscle mitochondrial function peak in the late afternoon, whereas low-energy sensitive signalling peaks in the morning.

• Exercise is a robust Zeitgeber of skeletal muscle clocks, and exercise can reset the molecular circadian clock, thereby effectively ameliorating the negative effects of disrupted sleep patterns.

• Optimizing the timing of exercise bouts could aid existing therapeutic interventions for the management of metabolic disease.

• Divergent modalities of exercise can interact with the circadian rhythm, resulting in potent metabolic effects

Before we get into this, I want to bring to importance of patterns and habits that you have or don’t have. Most important metabolic functions are timed; they occur in cycles throughout the day and night. You do too.

But to take advantage of the patterns is this: when you are grounded in good patterns, like when you go to bed, when you wake up, when you eat, when you workout and all the other mundane activities of your day and night, if you choose, you are able to stretch your creativity, your thinking, your planning, all the things your cerebral cortex is designed to do for you. But this is when the basic functions like I said above, are under some kind of cycle, pattern, or habit.

Now, let’s apply this to your muscles. Two things here. First, I’m calling this point “A” because I’m going to get a little deep and I want to make sure you circle around with me. So this is point A and that is the authors discuss the timing of exercise metabolism and how to take advantage for working out and improving athletic performance.

I want to get into this a little more but following the article, they discuss exercise physiology and circadian timing. They go on, and I’m not going to get very deep in this very scholarly article, but they discuss how that in the afternoon that the muscle functions are better. A couple of examples here. First, more world records are broken by athletes competing in the early evening, even when environmental conditions and scheduling bias are partially controlled. Increased strength, power and endurance are often observed in the afternoon and evening compared with early morning. And secondly, researchers have reported that athletes in the evening training groups gained more muscle mass than athletes in the morning training groups.

So just as muscles have a timing affect, you can use this timing to your advantage. You may want to workout or save your performance for the afternoon. Not too late, I imagine, they didn’t say, but you don’t want to workout way late in the afternoon or evening because you’ll be cutting into your parasympathetic cycle. You won’t be able to sleep very well.

Now, I’m circling around to “B”, what the authors mentioned but I think has a lot of possibilities. They mentioned it briefly but don’t get into it much. The term zeitgeber. I had to look this up. This is amazing. A zeitgeber is any external or environmental operant or condition that entrains or synchronizes an organism's biological rhythms to the Earth's 24-hour light/dark cycle and 12-month cycle. And what they’re saying is that “exercise acts as a robust zeitgeber of the muscle clocks, resetting the molecular circadian clocks”.

Isn’t that profound! Exercise can reset the timing, to a degree, of your body metabolism.

I have often wondered about the concept that activating the muscles, really engaging them to increase their metabolic capacity - their ability to function better than compared to not exercising - that this would improve even other functions indirectly related to them. In the case of insulin sensitivity, exercise does. In the case of heart function, exercise does this as well. In the case of neurological output, exercise does this as well. But I don’t think we’ve really seen all the profound effects that good exercise will bring. And by good exercise I mean an activity that engages the muscles to produce adaptations in function not realized prior to the exercise. In other words, exercise must produce metabolic, physiologic results. Or I wouldn’t call it exercise.

The authors continue. And we can call this point “C”. This has to do with the skeletal muscle clock and mitochondrial function. Get this. And I think this has to do with improved afternoon performance and that is that the mitochondria function is related to oxidative capacity; reduced oxidative capacity of the skeletal muscle is associated with decreased exercise performance.

That makes sense. The less ability to process oxygen in the muscles the less the exercise performance. This really makes sense for an athlete but it should make sense to anyone. If you can’t process oxygen because your muscles are “exercised” well, you’re going to be slow and tired.

Good news. The best way to improve mitochondrial function is to put your muscles through a good workout, and remember what a good workout is. In my opinion you have to work as many muscles, through their complete range of motion, against resistance, to exhaustion. What exercise can you guess I’m talking about. But it doesn't matter. Find the best exercise to do this. Don’t call walking exercise. Exercise is muscle fatigue to exhaustion.

To divert just a little; there are really two kinds of exercise: muscle building and cardio which is just muscle building to the heart. In each of these cases you want to workout the muscle to exhaustion. To speak directly to cardio - that is where High intensity interval training comes in - and to exercise the heart - you can’t take it out and run it on a machine - to exercise it you have to engage the most muscles as possible in an exercise that puts more exhaustive strain on the cardiorespiratory system than any other muscle. That’s the magic of high intensity interval training when it's done right.

There were a few more points in the article that discussed other powerful effects of exercise such as thermoregulatory response to exercise Exercise oscillates over the circadian cycle, so that you don’t dissipate core body heat as well in the morning as compared with the afternoon. Again, another reason to exercise in the afternoon and if you’re lucky enough, to have your athletic event in the afternoon, away from the morning.

And one other point, sleep. Sleep surveys have documented regular physical activity improves overall sleep quality. High-intensity exercise increased the plasma concentrations of the sleep-promoting molecule adenosine in rats.

This article has been about the circadian rhythms and exercise and what profound effects exercise has not just on the muscles but on the entire body. I don’t think there is one system in the body that is not positively affected with good, purposeful exercise.