FFF 116: Does It Matter When You Train? The Impact Of Exercise On Circadian Rhythm – with Dr Brendan Gabrial


In this episode, Scott and Dr. Brendan Gabriel about the effects of exercise on your circadian rhythm. Does it matter what time of day you train? They tackle the different conditions that can be affected by circadian rhythm, as well as shift work and its effects if you exercise before or after your shift.

Brendan took his undergrad and PhD in Aberdeen with focus on exercise physiology and skeletal muscle biology in terms of insulin resistance and the role high intensity interval training (HIIT) may play in preventing cardiovascular disease.

Then he carried on with his academic research in Stockholm, Sweden along with the titans of Scandinavian exercise physiology with a specific interest in exercise as a preventative treatment for diabetes.

In this episode, you will discover cool stuff about:

What is Circadian Rhythm?

Basically, circadian rhythm refers to the “clocks” in each cell of our body and how they oscillate. A region in the brain, called the SCN plays a role in regulating these clocks. The SCN is somewhat the “master clock” within the body that signals all these other clocks, keeping time effectively.

A few facets of evidence suggest the alignment of intrinsic genetic components to diabetes in terms of the clock, interacting with disrupted sleeping patterns. Hence, doing your best to optimize sleep is very important to prevent these metabolic diseases.

The Effect of Shift Work on the Circadian Rhythm

On a population-wide scale, shift work has been shown to increase one’s risk of developing these diseases. Additionally, each clock of the body is affected by a lot of different factors such as eating and exercise.

A recent study suggests that only four days of shift work was enough to induce moderate insulin resistance. Aging is another factor that affects the molecular clocks. However, it has also been shown that people who do a more structured shift work, are less associated with risk of disease than people who are constantly shifting.

To maximize the effects of a good night’s or good day’s sleep, have a good structured sleeping routine, combined with regular eating and exercise patterns throughout the week.

Effects of Exercise in Relation to Shift Work

There’s growing evidence that habitual training increases the robustness of these circadian rhythms and people who are fitter are able to withstand shift work and have less deleterious health impact from shift work.

The effects also depend on the exercise modalities done. Exercising before the shift is arguably one of the best candidates for the treatment of deleterious effects of shift work.

Best Time of Day and Consistency of Exercise

The ability to produce power and strength are greater in the afternoon. He recommends not to train really early in the morning, before 6am, and not to train too late at night.

Although it also depends on what time of day you’re acclimatized to training, in general, it doesn’t really matter what time of day you train. However, if you’re planning on training for a 10K or any high intensity event, train at the time the event is going to take place.

It’s better to keep exercising regularly than doing just one long exercise in the weekend. At best, exercise at least every other day.

Exercise and Diabetes

One study done in people with diabetes found that exercising in the morning increased their blood sugar whereas exercising in the evening, reduced blood sugar.

All this being said, don’t be afraid of exercise, even if you had to do it in the morning. Just be a little bit cautious about the intensity. In addition, the different modalities of exercise really interact with the molecular clock. Therefore, talk to your doctor before starting any exercise program, and think about the intensity. At least start with low intensity exercises if you had to do it in the morning.

As for people with shift work, eat, sleep, and exercise in a regular manner as much as possible.

  • What is a circadian rhythm
  • How are mutations associated with disruptive sleeping patterns
  • Factors that affect the circadian rhythm
  • The importance of having a good sleep routine and a good structured eating pattern.
  • The harmful effects of shift work and how to best implement it
  • The benefits of exercise on shift work
  • When is the best time of day to train
  • Why you shouldn’t train too early or too late in the day
  • How often should you exercise
Quotes & Take-Aways

The SCN is somewhat the “master clock” within the body that signals the to all these other clocks and keeps time effectively.

Trying to do everything one can to optimize sleep is very important in terms of preventing these metabolic diseases.

People who do shift work, which is more structured, they’re less associated with risk of disease than people who are constantly shifting.

There’s growing evidence that people who do habitual training have more robust circadian rhythm.

People who are fitter are able to withstand shift work and have less deleterious health impact from shift work.

If you want to optimize your exercise for health, you need to be exercising at least every other day.

Connect with Brendan:

Thanks for listening and the support – if you enjoyed this episode, I hope you can leave the podcast a rating and review on iTunes, and if you haven’t subscribed yet, this is the best time to do that too. This will help the show to get up in the rankings.

Scott Baptie

Scott is the owner and founder of Food For Fitness. He is a fat loss coach, speaker and fitness writer with a masters (MSc) degree in Applied Sports Nutrition.