Should you train in the morning or evening? While different times of the day can have various impacts on your training, the most important thing is to consistently train in the morning, afternoon, or evening. The circadian rhythm determines body temperature and hormones such as testosterone and cortisol in a 24-hour cycle. This could theoretically make training at certain times of the day more appealing. However, the body can become so accustomed to training at a specific time of day that making a consistent choice in this regard may be the most important.
Endogenous and Exogenous Factors
When choosing between training in the morning, afternoon, or evening, several variables must be considered. In practice, it’s often factors such as available time, rest, and nutrition that determine the outcome. In many cases, the choice between morning, afternoon, or evening training is determined by opportunity. Simply put, the time we have available alongside work, study, or other daily commitments. However, there are, albeit limited and varying from person to person, sometimes days when we have the choice to determine the time of day ourselves. Those one or few days a week when you are free and/or can decide when to train. Decisive factors in such cases usually include statements like: “It’s too crowded at the gym in the evenings” or “I’m not awake enough in the mornings and haven’t eaten enough yet.”
However, you can also consider which time your body finds most suitable for this. Taking into account other factors may help you get more out of your efforts. Think especially of the so-called circadian rhythm and its effect on testosterone and cortisol, as well as environmental factors such as temperature at different times of the day.
Ultimately, two types of factors play a role:
- Endogenous factors: Influence from within the body
- Exogenous factors: Environmental influences
Exogenous Factors: Environmental Influences
Environmental factors mainly include:
- Sunlight
- Temperature
- Humidity
Endogenous Factors: Circadian Rhythm
The circadian rhythm is also known as the sleep-wake rhythm or 24-hour rhythm (1). The circadian rhythm is determined by “biological variations that repeat themselves every 24 hours” (2). The circadian rhythm ensures that certain processes are more active or less active at certain times. Think of things like:
- Body temperature
- Release of hormones such as testosterone and cortisol
- Blood pressure
- Alertness
Without the influence of environmental factors, the circadian rhythm would persist. This “biological clock” is controlled from the brain (specifically the nucleus suprachiasmaticus in the hypothalamus, or “SCN”) (3,4). In practice, the biological clock takes into account environmental factors. For example, the amount of light plays a role in the production of the hormone melatonin, which induces a sleepy feeling. The image below shows how many processes are influenced by this clock (5).
Testosterone and Cortisol in the Circadian Rhythm
The image shown above comes from the work of researchers at the University of the West of Scotland (5). You can see that, among other things, testosterone and the stress hormone cortisol are influenced by the circadian rhythm (6). Testosterone is naturally a significant player in determining muscle strength and mass. This applies particularly to “free testosterone,” testosterone that is not yet bound to sex-hormone-binding-globulin, or SHBG, and albumin (5). This free testosterone (about 0.5-2% of total testosterone) is still available to exert its influence on muscle cells. It works anabolically and instructs cells in muscles to produce more protein, causing them to grow.
On the other hand, cortisol works catabolically and, under the influence of stress (literally “load”), causes breakdown of muscle mass in favor of energy. However, it also increases your metabolism by burning fatty acids.
Strength training, on one hand, causes your body to release more testosterone to respond to the training by repairing the (intentionally caused) damage from the training. On the other hand, more cortisol is also released because the body senses an increased need for energy and wants to meet this need.
Ultimately, it is the ratio between testosterone and cortisol, the so-called T/C ratio, that determines whether and to what extent these hormones contribute to muscle growth and increase in muscle strength (7). If this balance, for example, shifts in favor of cortisol, it is often an indication of overtraining (8), although opinions on this matter constantly differ.
Basin the Training Time on Testosterone and Cortisol?
Cardio in the Morning?
The levels of both testosterone and cortisol are highest in the morning before daily activity begins. In the evenings and nights, they are at their lowest (9). The increase in cortisol in the morning thus causes increased fat burning, but also protein breakdown to provide more glucose in the blood for daily activity (10). The reason for the increase in testosterone is possibly to limit the muscle-breaking effect of cortisol (11).
For some people, this is a reason to do cardio mainly in the mornings to benefit from the increased fat burning. However, for strength training, this seems to be a less suitable time due to the high degree of muscle breakdown caused by cortisol. Cortisol fluctuations show greater differences throughout the day than testosterone. Compared to the highest value during the day, testosterone decreases by about 42%, while for cortisol, this is 60% to 92%, depending on the measurement method used (13,12). So, you can imagine that there are other times of the day when the balance between testosterone and cortisol is more favorable to strength training.
Strength Training in the Evening?
There are indeed indications that, due to this relationship, evenings are more suitable for strength training than mornings. Testosterone is at a relatively high level at that time, while cortisol is at a relatively low level. In this case, you will experience more of the anabolic effects of testosterone and fewer of the catabolic effects of cortisol.
However, as mentioned before, the body can become so accustomed to training at a specific time of day that making a consistent choice in this regard may be the most important.
Translated and adapted from “Wanneer trainen: ‘s ochtends, ‘s middags of ‘s avonds?” by Guido Vos published at Fit Society (source).
