Resistance training is a common form of exercise using calisthenics or weights. There are a number of benefits to this form of exercise, primarily centered around maintaining muscle mass and bone density.

I get asked 2 questions quite a bit. They are:

1. What is the best type of exercise?
2. Is exercise a good option for improving circadian rhythms?

The answer to the first one is easy. The best type of exercise is the type you do without hesitation. For some that means going to the gym, for others it means playing tennis or running.

However, there are a few bars you have to meet for getting the most out of exercise. IMO, to get the most out of exercise you should tax both your muscles and your cardiovascular system. For example, I like resistance training with weights, plyometrics, and running.

To answer the second question, we’re going to dig in to some pretty cool evidence. But to answer that question, no, exercise isn’t a good option for improving circadian rhythms…It’s essential.

Resistance training, circadian rhythms, and NAD+

By now you’ve probably heard of something called NAD+. NAD+ is a co-factor in energy metabolism. It’s the darling of anti-aging research, as age-related decline in NAD+ levels may drive some aspects of the aging process.

Currently, there is quite a bit of enthusiasm behind NAD+ boosting supplements such as nicotinamide riboside(NR) and nicotinamide mononucelotide(NMN). In mice and other model organisms, these NAD+ precursors improve age-related decline.

But how do they do this? Well, a recent paper suggests that part of the problem in aging is that declining NAD+ levels drive age-related circadian disruption in the liver. Moreover, supplementing mice with NR restored the age-related disruption in circadian rhythms by restoring NAD+ levels.

An interesting finding, but the dosage used in this study was huge, and it’s not a human study. The only human study found that supplementation of NR increased NAD+ in immune cells by 60%. It’s also important to point out that in the mouse study above, NAD+ supplemented mice became more active, which may have driven some of the increase in NAD+.

To put this into perspective, a recent study in humans found that 10 weeks of resistance training doubled NAD+ levels in muscle in older, overweight people. This effect brought their muscle NAD+ levels up to par with college-aged men.

But what does this mean, exactly?

Metabolism: The language of the human body

Circadian rhythms are biologically processes that follow an approximately 24 hour period. Though every one of us beats to our own timing genetically, our clocks are reset everyday by exposure to time-setting cues called zeitgebers.

Think of the timekeeper in our cells as an hourglass. Some of us have an hourglass that runs long, some run short. As a result, some of us are genetically more likely to prefer the morning vs the night, while others fall somewhere in between.

Be that as it may, our exposure to various environmental factors cause us to flip the hourglass in our cells everyday. So even if your hourglass causes you to run at a different time, exposure to light, feeding, and temperature cycles resets the clock so that we run on time.

But, there’s a problem. There are 11 organ systems in the human body that all need to communicate with one another. Furthermore, there are trillions of cells that make up all these organs systems that need to synchronize with one another so that they all run at the same time.

In order for this to work, they all need to speak the same language. That language, is our metabolism. And this is where NAD+ comes in.

Resistance training, metabolism, and our clocks

As I mentioned, NAD+ plays a starring role as a cofactor in energy metabolism. But, it also helps regulate gene expression and DNA repair via proteins called sirtuins.

Sirtuins/NAD+ act as the metabolic arm of circadian rhythms. The environmental cues that set circadian rhythms mentioned above need to be translated in to a language our cells understand in order to flip the hourglass.

The activation of sirtuins accomplishes this effect by changing genetic expression through a process called histone deacetylation. Sirtuins are known as histone deacetylases(HDAC), and this process is what tweaks the circadian clock.

However, sirtuins require NAD+ as a cofactor. Without adequate NAD+, sirtuins can’t act as HDACs and therefore, can’t affect our hourglass. So even if you have the appropriate exposures, your cells can’t sense them.

This is why restoring NAD+ levels in mice reversed age-related disruption of circadian rhythms. It’s also why exercise is essential to optimizing circadian rhythms. Note: I covered the importance of NAD+ for circadian rhythms/aging in previous blogs you can find here and here.

Conclusion

As we get older, we experience circadian disruption. As a result, we become more prone to sleep disruption, metabolic dysfunction, and chronic disease. We can attenuate some of this by getting the proper exposures to light, the feeding/fasting cycle, and other zeitgebers that help reset our circadian rhythms every day.

However, it’s not simply poor exposure to zeitgebers that drives age-related circadian disruption. As we get older, our NAD+ levels decline which makes our circadian clocks go haywire. Restoring NAD+ levels in mice reverses age-related circadian disruption.

Resistance training is a safe, effective, and proven method for improving age-related decline in multiple systems. While the focus is typically on the benefits to muscle and bone, the metabolic benefits indicate resistance training is essential to maintaining NAD+ levels and, therefore, robust circadian rhythms.