My PT teachers professes working-out/training in early morning hours is the best time to do so. A quick search on benefits of morning walk (or similar phrases) reveals a lot of information which seem to be backed by sound scientific evidence. In fact it is common wisdom around the world, across all cultures.

Okay - accepted. But why is it beneficial in first place? Because there is plenty of oxygen in the morning; or is it?

After long hours of darkness (plants respirating at night) when first light comes plants would have just started photosynthesis, that too at a pretty slower rate (owing to lower intensity of light at dawn). In fact I remember having read something about compensation point

The (light) compensation point is the amount of light intensity on the light curve where the rate of photosynthesis exactly matches the rate of respiration. At this point, the uptake of CO2 through photosynthetic pathways is exactly matched to the respiratory release of carbon dioxide, and the uptake of O2 by respiration is exactly matched to the photosynthetic release of oxygen. SRC

So now, obviously, we can establish the fact that concentration of oxygen should be/is much lower than carbon-dioxide in early morning hours.

  1. So why morning walk or early morning exercises?
  2. If oxygen content is important why not exercise in early evening hours because not all people would like an endurance drill at theoretically perfect time of noon :)?
  3. Is there some other mechanism makes oxygen content more than carbon-dioxide content in the morning?

Personally - I do feel more fresh in the morning hours but maybe that is because of my internal biology, correct me if I am wrong.

P.S. I am not a biology student, so pardon my ignorance.

  • $\begingroup$ Personally, I would argue with the premise that it's more beneficial. Of course I have no data to support this, because (bar a long-ago stretch in the military) morning exercise is just not something I'm going to do. $\endgroup$
    – jamesqf
    Apr 21, 2015 at 18:31

5 Answers 5


1: The only benefit I've heard of scientifically is to do with the circadian rhythm. I heard a talk that basically said a dose of bright light in the morning can help set hormonal levels to a daily rhythm. This seems to suggest the same.

2 and 3: I think the overall oxygen levels would not be significantly different at different times of day, but pollution levels might be, this might be relevant.

edit: didn't realise this was such an old thread...


I am going to play the devil's advocate here.

I don't know if working out within the first three hours of waking is necessarily the best time to do so. In the morning, we have what is called cortisol awakening response which is where the body releases cortisol. Cortisol is a by product of the sympathetic nervous nervous system. Dr.s James E. Muller, Geoffrey H. Tofler, and Richard L. Verrier in their article Sympathetic Activity as the Cause of the Morning Increase in Cardiac Events said that early morning activity is a likely culprit but only circumstantial in sudden cardiac infarction [1]. However, Dr.s Douglas P. Zipes and Hein J. J. Wellens in their article Clinical Cardiology: New Frontiers Sudden Cardiac Death found that:

Time of day is also important, with more sudden cardiac deaths, strokes, and myocardial infarctions occurring in the morning on arising from bed, perhaps related to increased sympathetic discharge in response to venous pooling that then triggers increased blood viscosity and platelet aggregation [2].

In Exercise and Acute Cardiovascular Events in Collaboration With the American College of Sports Medicine and Dr.s Paul D. Thompson, FAHA, Co-Chair; Barry A. Franklin, FAHA, Co-Chair; Gary J. Balady, FAHA, Steven N. Blair, PED, FAHA; Domenico Corrado, N.A. Mark Estes III, FAHA; Janet E. Fulton, Neil F. Gordon, William L. Haskell, FAHA, Mark S. Link, Barry J. Maron, Murray A. Mittleman, FAHA, Antonio Pelliccia, Nanette K. Wenger, FAHA, Stefan N. Willich, FAHA, and Fernando Costa, FAHA, felt they that didn't have enough data on claiming early morning exercises and sudden cardiac death (SCD); however, early morning SCD occurred in adults whereas for teens it SCD occurred in the afternoon [3] but "vigorous exercise, however, transiently increases the risk of acute myocardial infarction (AMI) and SCD, even in exercise-conditioned individuals, and several strategies are recommended to potentially reduce this risk"

Active individuals should know the nature of cardiac prodromal symptoms and seek prompt medical care if such symptoms develop.

That is, I wouldn't claim victory for working out as soon as you rise the best choice. However, I am not suggesting that you don't work out in the morning either but just be carefully about it. The best time to workout is the time that will allow you to be consistent, get in at least 30mins, and keep you motivated. If that time is the morning, just be aware of what is going on in the body.

Additional article found in support of afternoon/evening training

Serendipitously, I stumbled across an article on swim performance and time. The article found that the best performance was afternoon to evening and not in the morning [4]. This was published in 2007 in the Journal of Applied Physiology.


I would offer the counter point that this has to do with energy availability. (I'm on my phone so I can't put in references just yet). But there was just a great recent study published in Science (I'll go find it), in which a group looked at plaque deposition as a proxy of overall cardiovascular health of groups of mice exercised before and after food intake. They find that exercise under fasting conditions, which would be akin to morning running, appears to be significantly more protective against cadiovascular disease than exercise after feeding. This is also consistent with some human data suggestive of fasting exercise benefits as well. In a separate experiment the mice were fed the same number of calories per day, but those that were exercises after sleep and before eating were significantly leaner and had less plaque deposition in their vasculature.

In part the idea is that after a period of fasting exercise will promote scavenging of residual cholesterols in the vasculature as well as cellular autophagy (which promotes "fixing" of current cells rather than just replacing them). To the layman, Resveratrol from red wine is probably the most commonly known way in which autophagy might be promoted. But in general think of periodic fasting and feasting as protective because it can help maintain metabolic homeostasis and prevent unnecessary cell turnover.

Hopeful that helps lead you in the right direction. Metabolics and aging is a huge and exciting field and this question could be answered with a small textbook. But you should at least understand that this field is far from being well understood. And that your PT teachers may end up being right, but this field still quite primitive, and this is not accepted yet or really understood by the scientific community.

  • $\begingroup$ Did you forget to look up the links? I am rather interested in looking up this study that you have cited. $\endgroup$
    – March Ho
    Apr 28, 2015 at 7:59
  • $\begingroup$ You know, I've looked and I can't seem to find it. Unfortunately, not being my field of concentration I never saved the reference. I'll keep looking but I can't seem to find it in science, so it may have been in nature or cell, though I looked and can't seem to locate the study. Sorry. $\endgroup$ Apr 28, 2015 at 16:32

If walking in the morning is truly more beneficial than walking at a different, it certainly wouldn't be related to atmospheric oxygen content. The oxygen content of the atmosphere fluctuates on the timescale of years, not hours. And keep in mind that when it's morning where you are currently, it's going to be noon somewhere else, and dusk somewhere else.

  • $\begingroup$ W.r.t. keep in mind that when it's morning where you are currently, it's going to be noon somewhere else, and dusk somewhere else - But the distance between morning & noon would be several longitudes, oxygen, under the effect of diffusion or even torrential winds, wouldn't normalize its concentraion so quickly. $\endgroup$
    – RinkyPinku
    Apr 22, 2015 at 9:11

Morning walks are preferred because the sunlight that falls on the earth in the morning is good for your skin for producing Vitamin D. and also it is said that morning walks are good for:

Strengthening Bones and Joints

Weight control

and also independent of the time of the day, due to exercise and walking you keep moving your joints an this improves your Blood circulation.

And also as you keep moving your muscles too which improves Muscle Strength .

this was from my knowledge.If you want to know more :

Click Here(link 1) || and here(link 2)

Share your thoughts with comments,

Any suggestions and questions welcomed,

Anurag .

  • 4
    $\begingroup$ This is nothing I would attribute only to a morning walk. Vitamin D will be produced as well in all other parts of the day during sun exposure, the training effect as well. $\endgroup$
    – Chris
    Apr 28, 2015 at 6:58
  • 1
    $\begingroup$ Ditto, there is no difference in the sunlight hitting the earth at different times of day. edit, other than intensity. $\endgroup$ Apr 25, 2017 at 11:11

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