In looking for the best time of the day to exercise we are really looking to answer the question “How can I achieve more with less effort?” This is both natural from a human perspective and desirable from an evolutionary one. If we can, somehow, get more health and fitness benefits from exercise we are more likely to engage in it regularly. If the exercise we engage in delivers more health and fitness benefits per minute we are achieving our goal of remaining healthy in our mind and body, in our life, for as long as possible.
Unsurprisingly scientists have been looking at this space for some time now. A 1996 study[1] looked at circadian rhythms in the body and the body’s rhythm that determines our metabolic system and hormone production. That study, back then, determined that there were better times of the day to exercise for athletes and that older athletes did better in the morning as they experienced “morningness” - a surge of energy early in the day that was not always present later in the evening.
A much later study published in 2019[2] bore out a lot of this further by linking the mechanism that releases melatonin in the body with the body’s preparedness for action. A study carried out in 2015[3] focused on aerobic exercise and endurance and determined that despite the fact that the body appeared to be more prepared for action in the morning, endurance exercise carried out in the evening produced a lot more adaptations and led to faster increases in endurance performance.
Many of the studies carried out to determine which part of the day is best to exercise at so we get better results note that “time-dependent exercise has different outcomes, based on the exercise type, duration, and hormone adaptation.” This means that while exercising at different times of the day produces different results[4] the difference in the results depends upon so many variables that it has not been easy to say exactly what it is that makes the difference.
This, in turn, has made it hard to determine what guidelines to give in order to help those who exercise, pick a ‘best’ time to do so.
Massive Study In Effects Of Exercise In Morning And Evening
Trying to understand exactly why exercise has such different effects on us at different times of the day and why different types of exercise activate adaptations depending on the time of the day, researchers from around the globe cooperated in a large-scale study that examined both time-specific and exercise-specific effects.
This latest study[5] confirmed what we already know: Different exercises work to change our body differently in the morning than they do in the evening and the same exercises performed in the morning have a different effect on us when performed in the evening.
It also unearthed why this happens. Our body is in a constant state of balance, called homeostasis. This is a process that maintains stable, internal physical and chemical conditions and it is what helps keep us alive. Yet, our body lives in a constantly changing external environment. This means that in order to maintain our internal, stable state it has to constantly adapt throughout the day to external conditions which include fatigue and the amount of energy that is available to us.
The study showed that when we exercise a complex web of interactions take place. Organs talk to the body and the brain and each other. The brain talks to many different organs. The body, as a whole, is engaged in a complex web of interactions which take into account circadian rhythms, the amount of sleep we have had, how tired we are and how much energy we have left ‘in the tank’.
Consider, for example, how cardiovascular activity done in the evening creates fewer adaptations that help with cardiovascular endurance, than the same activity done in the morning, but it produces a higher calorie burn for the same effort.
Just this piece of information is important. Someone who is trying to lose weight, let’s say, would do better to run in the evening, while someone who was looking to enhance cardiovascular and aerobic fitness should consider running in the morning.
Conclusion
Despite the number of scientists involved in this latest study on the best time of the day to exercise the consensus is what it has always been: The best time of the day to exercise is the time of the day you can. You worry about specific effects and adaptations only when you have very specific, high-level goals, like the ones faced by Olympic athletes of top-level athletic competitors.
The rest of us should do what we have always done: find the time to get some exercise in and monitor our body and what we do to determine, for ourselves, what realistic changes we can make to our exercise routines so that we get the most out of them.
References
1. Atkinson G, Reilly T. Circadian variation in sports performance. Sports Med. 1996 Apr;21(4):292-312. doi: 10.2165/00007256-199621040-00005. PMID: 8726347.
2. Serin Y, Acar Tek N: Effect of Circadian Rhythm on Metabolic Processes and the Regulation of Energy Balance. Ann Nutr Metab 2019;74:322-330. doi: 10.1159/000500071
3. Kim HK, Konishi M, Takahashi M, Tabata H, Endo N, Numao S, Lee SK, Kim YH, Suzuki K, Sakamoto S. Effects of Acute Endurance Exercise Performed in the Morning and Evening on Inflammatory Cytokine and Metabolic Hormone Responses. PLoS One. 2015 Sep 9;10(9):e0137567. doi: 10.1371/journal.pone.0137567. PMID: 26352938; PMCID: PMC4564197.
4. Seo DY, Lee S, Kim N, et al. Morning and evening exercise. Integr Med Res. 2013;2(4):139-144. doi:10.1016/j.imr.2013.10.003
5. Shogo Sato, Kenneth A. Dyar, Jonas T. Treebak, Sara L. Jepsen, Amy M. Ehrlich, Stephen P. Ashcroft, Kajetan Trost, Thomas Kunzke, Verena M. Prade, Lewin Small, Astrid Linde Basse, Milena Schönke, Siwei Chen, Muntaha Samad, Pierre Baldi, Romain Barrès, Axel Walch, Thomas Moritz, Jens J. Holst, Dominik Lutter, Juleen R. Zierath, Paolo Sassone-Corsi, Atlas of exercise metabolism reveals time-dependent signatures of metabolic homeostasis, Cell Metabolism, 2022, ISSN 1550-4131.
