The morning? Maybe. The afternoon? Maybe.
Like everything in health in fitness, it depends. Many things, such as your goals (fat loss, muscle gain, general health), your schedule (it doesn’t matter what time is optimal if only one time is available), and personal preference will all impact what time of day is best for you to workout. Check out this guest post by personal trainer Maya Wright to learn more!

For the purposes of this post, we will be looking at this from a physiological perspective, more specifically, how our natural Circadian Rhythm can impact our results.

A Circadian Rhythm is the approximate 24-hour cycle that our bodies go through to prepare us for daily environmental changes. While there are many aspects to our Circadian Rhythms, we want to focus on two in regard to workout timing: our body temperature, and our hormones.

Body temperature

Our body temperature is lowest in the morning, dramatically increases upon waking, and peaks in the early evening. Some studies suggest this allows for greater performance later in the day when the body is in a naturally warmer state. During this time it is believed our bodies are more adept at utilizing carbohydrates over fat as a fuel source, and there is greater facilitation of actin-myosin crossbridge mechanics in our muscles. This essentially means we achieve higher levels of muscle activation during this period.(1)


In regard to Circadian Rhythms, the two hormones that you will see come up again and again are testosterone and cortisol. Testosterone is an anabolic hormone that helps us build muscle and develop strength. Production of testosterone is high at night and is low during the day. Cortisol, on the other hand, is a catabolic hormone that mediates the breakdown of muscle to create energy and inhibits muscle growth. While cortisol is a vital steroid hormone, continually elevated levels can seriously mess with your progress (both through increased muscle breakdown, and by inducing insulin resistance). Cortisol is low at night, peaks upon waking, and gradually decreases throughout the day. The basic idea here is that for muscle building, we want to workout during the time of our optimal T/C ratio, which tends to be in the second half of the day.(2)

Muscle gain

While studies(3) suggest an increase in muscle gain in the evening, there can always be limitations for studies such as these. For one, the study only lasted 24 weeks, which sounds like a decent amount of time, but is a relatively short window of time to determine the long-term results. Another thing to keep in mind is a majority of studies are only conducted on men. Men and women often have different physiological responses to the same stimulus, meaning these studies potentially have less relevance for women, or could even be the opposite.

Further complicating results, there are studies showing we can adapt our performance through specific time-of-day training.(4) In other words, if you are consistently training in the AM, your body will adapt to that, and visa versa for PM.

All is not lost for those dedicated early birds. Researchers at Appalachian State University found that morning workouts lead to a decrease in blood pressure and superior sleep quality, which have huge positive implications for health. (5) (It is worth noting this study was done only on aerobic exercise, not strength training).

My takeaway: It is far more important to develop a consistent weekly workout schedule than to try to achieve a “perfect” workout time of day. By doing so, you will make progress towards your fitness goals in a manner that is sensible for your particular schedule and lifestyle. That said, if you have perfect freedom and control of your daily schedule, try afternoon workouts for strength gains or morning workouts for a better night’s sleep!


Hyatt Training is a collective of certified, enthusiastic and innovative personal trainers in Portland, Oregon. To read more exercise-related posts like this one, follow this link.