The Best Time To Workout, According To Science (Part 2)

In part one of this article (which you can read here), we took a tour through the human body’s first half of the day specifically through the lens of our natural circadian rhythms. In part two, we will finish up that tour so we can better understand our bodies’ natural cycle and how we can time our workouts with that cycle for maximum success.

At 5 pm, humans exhibit their greatest cardiovascular efficiency allowing for maximal exercising or hunting. This also occurs during a period of time when we have our best rates of protein synthesis in our body. This is why exercise should be optimally done in this window.

When the sun falls at 6 pm, we begin to see a major change in the cardiovascular system about a half hour later—at 6:30 pm, we see high blood pressure again due to changes in atrial natriuretic factor and antidiuretic hormone (ANF, ADH) in the renin-aldosterone axis.

Once this occurs over the next 30 minutes (7 pm), we begin to see a gradual rise in our body temperature as leptin (and IL-6) is released from our fat stores, with agouti’s help, slowly after dinner is eaten to signal the brain about our fat mass and inflammatory status. Agouti is, yes, a furry little rodent, but also a neuropeptide produced in the brain that has a powerful signaling effect to increase appetite and decrease metabolism and energy expenditure, which is why it is known as one of the most potent and long-lasting appetite stimulators.

For the next two to three hours, leptin levels slowly rise as insulin levels fall. Adiponectin levels also fall during this time frame. These fat hormone signals are what activate the adenosine system in our bodies. Adenosine is created over the course of the day; you start in the AM with low levels, and as they build, high levels of adenosine lead to sleepiness.

Therefore, morning exercise and exercise done from around 3:30—5 pm are ideal according to our circadian rhythm. However, it is also important to consider the kind of day you have had. If you have had a stressful day or a busy day, if you feel really tired, then exercising may not be the best idea, as it can put a strain on your body and heart (something that has been discussed on the B.rad podcast before). If a 5 pm workout works well for you, then great! But most of us lead very busy lives, with varying levels of stress on top of it, which makes the morning such an ideal time for exercise. Not only is it aligned with our body’s natural circadian rhythm, but it also functions as a sort of safety net—if the day passes by quickly and all of a sudden it’s 5 pm and you’re already exhausted, you’ll be happy you already worked out. Morning exercise also offers additional benefits such as:

  1. Increased energy levels: Morning exercise can help you feel more awake and maintain a steady, stable feeling of being energized throughout the day.

  2. Improved mood: Exercise releases endorphins, which can help boost your mood and reduce feelings of stress and anxiety. In addition, doing something that you know has a positive effect on your health also boosts your mood since you’re starting the day off with productive activity. 

  3. Better sleep: Exercise can help regulate your sleep cycle and improve the quality of your sleep, particularly if it is done outside.

  4. Increased metabolism: Morning exercise can help kickstart your metabolism, which helps weight loss efforts and helps to maintain a healthy weight.

  5. Reduced risk of chronic diseases: Regular exercise can help reduce the risk of chronic diseases like heart disease, diabetes, and certain types of cancer. Looking good naked is also a nice bonus, but don’t forget what Herman Pontzer once said on B.rad: “You exercise for everything you don’t see.”

  6. Improved cognitive function: Exercise has been proven to improve memory, concentration, and overall cognitive function.

  7. Increased self-confidence: Regular exercise can help improve your self-confidence and self-esteem, which will undoubtedly have a positive impact on all areas of your life.

While I love to go for a post-dinner walk with my dog, I tend to save my workouts for the morning (I also weave in micro-workouts throughout the day). I’ve tried working out at different times (sometimes you have no choice and have to get it in whenever you can!) but I have learned from starting my mornings with my mobility/flexibility movement routine for the last six years that this is the time that works best for me. It’s energizing and it makes me feel good—not just physically but mentally too—by setting the perfect tone for a productive, focused day. But what works for me may not work for you, and there are definite benefits to a 5 pm workout since it honors our circadian rhythm and the time when our bodies are in optimum condition for peak physical performance. It all comes down to listening to your body. 

When sleep expert and RiseScience founder Jeff Kahn was on B.rad, he revealed: “We all have a genetic amount of sleep we need.” Genes play a major role in our sleep, and Jeff explained when he was on the show that when people say, “I’m a night owl” or “I’m a morning person,” this is not just a preference, it’s a biological phenomenon that we don’t have control over. Jeff added, “There are ways to become more of a morning person or become more of a night person….but it is largely biologically determined.” This is pertinent because research has found that evening exercise harms sleep quality for early risers, but not for night owls. So when it comes to timing workouts, seek to honor not just your circadian rhythm, but also your body and your own unique set of genes. If you feel better exercising in the afternoon, then it’s probably for a good reason. 

I’d love to hear how you time your workouts, so send your comments and any questions to podcast@bradventures.com. Tell me what time you like to exercise, and if you prefer the afternoon, the evening, or if you’re like me and like to get it done as early as you can. If you’re not regularly working out or need some help and inspiration getting started, click here to learn more about my Morning Routine online course—a comprehensive, multimedia educational experience that will help you seamlessly incorporate this life-changing practice into your daily life.


Brad Kearns
Brad Kearns
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