Why Rest Days Are Important

In this edition of the newsletter, I’d like to talk about rest days, which are an often overlooked aspect of fitness and improving physical performance. The latter is a critical aspect of your health journey, so don’t dismiss this month’s email too quickly — even if you’re not an athlete!

How are health and fitness related?

A few years ago, my wife got certified as a CrossFit Level 1 Trainer. And part of her curriculum was to learn about the Sickness-Wellness-Fitness continuum.

CrossFit proposes that sickness, wellness and fitness are different measures of a single quality: health.

In other words, you can improve your health (as measured by blood pressure, body fat, bone density, etc.) by improving your fitness. 

I mostly agree with this framework, but I realize there might come a point in your fitness journey where becoming even fitter could be detrimental to your health. For example, if you’re a pro athlete, using performance-enhancing substances can help improve your performance (as their name implies) but I’m not convinced they’ll improve your health in the long run.

I also believe that true fitness must encompass certain aspects of metabolic biomarkers, including CRP, fasting insulin, gut health and others (see this blog post for a comprehensive overview of metabolic health). If you ignore those biomarkers, you might appear fit but not be healthy. 

When I was a pro athlete in my early twenties, I looked fit but I wasn’t healthy, because I solely focused on my exercise regimen while ignoring other aspects of my health, including diet, sleep and recovery. 

Let’s focus on recovery.

Most people think that exercise is what improves their fitness. For example, if you lift heavy weights, you get stronger. But strenuous physical activity is a stressor for the body that makes you weaker (at least, temporarily) by breaking down muscle tissue and inflicting “damage.”

Just think about your last “leg day” when you left the gym feeling so sore that, by the next day, you could barely walk. Chances are that you didn’t feel particularly strong.

What makes you stronger isn’t so much the work itself, but the recovery. It’s the repair process that follows those “micro injuries,” through a process of adaptation. So it’s important to give your body plenty of time to allow for those repairs to happen. 

If you don’t, you’ll slow down your progress and increase your risk of injury. Neither is going to help you become fitter and healthier.

But besides the obvious consequences of overtraining, not giving your body enough rest also has negative effects on your endocrine system (i.e., your hormones). 

For example, overtraining can negatively influence your sex hormones, including testosterone, leading to decreased bone density, increased injury rates and a decreased adaptation to training. 

For example, a 2018 study in the journal Hormones found that male athletes training over seven hours per week had a 10% reduction in testosterone levels after one year of training, and a 30% reduction after five years of training.

So if you’re one of those fitness enthusiasts who enjoy hitting the gym every day — maybe because not working out makes you feel lazy, or because you’re trying to compensate for too much (of the wrong) food — I’d seriously reconsider that approach for the sake of your health and your fitness.

Don’t get me wrong: if you’re an elite athlete, you might benefit from periods of intentional overreaching, followed by adequate rest. But for the average Joe (that includes me) and people who just want to exercise to improve their overall health, sufficient rest is crucial. 

I used to do CrossFit workouts five or six times per week, combined with rides on my AI-powered reduced-exertion high-intensity interval training bike or running while wearing a 20-pound weighted vest. In other words, I accumulated seven to eight workouts in some weeks. And they took a toll on my body.

Considering that I’m 40 years old, and knowing that my body doesn’t recover as quickly as that of a 20-year-old, I decided to reduce my training volume and better listen to my body.

These days, I do CrossFit three times a week and I sprinkle in a bike ride or two. On days that I don’t work out, I go for a 45–minute walk with our dog. 

Coincidentally, my performance has not decreased but some of my stubborn injuries (which were started by small changes in soft tissue and that progressed with overuse) have resolved. 

Plus, I’m less stressed about filling my week with workouts, as I discussed in my previous newsletter.

The bottom line is that if your goal is to improve your fitness and health, you need adequate rest. Stressing your body with intensive workouts every day is counter-productive. If you feel like you need to burn calories to make up for a less-than-ideal diet, consider making some changes to your diet — perhaps paired with implementing intermittent fasting.

And keep in mind that you can’t out-exercise poor dietary habits, regardless of how many calories you burn.

How to Tell If Your Body Needs More Rest

While some people may be sufficiently in-tune with their body to know when they need a recovery day, I’d argue that most hobby athletes (and even some elite athletes) have no idea whether or not they’re resting enough.

One way to find out whether your body is recovering well is to check certain blood markers, including creatine kinase (CK), which is a proxy for muscle damage. Some elite athletes keep tabs on those blood markers to manage their training load.

However, for most of us, drawing blood just to find out if we’re overtraining is probably overkill. A less invasive way to keep tabs on how your body is responding to physical (and mental) stressors is by monitoring heart rate variability. 

HRV is the difference in timing between heartbeats, and it’s an excellent indication of how the nervous system is responding and adapting to intense workouts (and other lifestyle factors). 

That’s one of the reasons why I’ve been wearing the WHOOP Strap since 2019. WHOOP is a health and fitness tracker that gives me a recovery score every morning, which helps me plan my workouts and avoid chronic overtraining. 

You can check out my in-depth reviews of WHOOP on my blog and YouTube channel to learn more. And you can learn how to improve your HRV here.

MK Supplements now has its own Instagram account. Going forward, I’ll post any brand/product-related content on the @mksupps account while my personal account will continue to feature blog content, product reviews and some insights into my personal life.

So I encourage you to follow both!

New Articles and Videos You Might Have Missed

Since the last newsletter, I’ve been busy creating new content and updating older articles with fresh information, including the following:

As you can see, I spent a lot of time updating older content to keep it fresh and relevant, as well as recording new videos for my YouTube channel. Check it out and subscribe if you like the videos, as doing so will help me grow the channel!

That’s it for May. I’ll be watching the CrossFit semifinals in Knoxville, Tennessee, this weekend so check out my Instagram for some selfies with my favorite athletes!

Until next time,
​Michael