Training in the Morning or Evening?

Is it better to train in the morning or evening? Although different times of day can have various effects on your training, the most important thing is to train consistently in the morning, afternoon or evening. The circadian rhythm determines, among other things, body temperature and hormones such as testosterone and cortisol in a 24-hour rhythm. In theory, this could make training at certain times of day attractive. However, the body can adapt so well to training at a certain time of day that making a consistent choice may be the most important factor.

Endogenous and exogenous factors

When choosing between training in the morning, afternoon or evening, several variables have to be taken into account. In practice, it is often factors such as available time, rest and nutrition that are decisive. In many cases, the choice between training in the morning, afternoon or evening is simply determined by opportunity. Simply the time we have alongside work, study or other daily obligations. Still, although this is limited and differs per person, there are sometimes days when we can choose the time of day ourselves. That one day or those few days a week when you are free and/or can decide when you train. The decisive factors then are usually things like: "In the evening the gym is too busy" or "In the morning I am not awake yet and have not been able to eat enough."

However, you can also ask yourself which moment your body finds most suitable for this. Taking other factors into account may allow you to get more out of your efforts. Think in particular of the so-called circadian rhythm and the effect it has on testosterone and cortisol, among other things, but also of environmental factors such as the temperature at different times of day.

Ultimately, two types of factors play a role:

• Endogenous factors: influence from within the body
• Exogenous factors: environmental influences

Exogenous factors: environmental influences

With environmental factors we should mainly think of:

• Sunlight
• Temperature
• Humidity

Endogenous factors: circadian rhythm

The circadian rhythm is also called the sleep-wake rhythm or 24-hour rhythm (1). 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 moments. Think of things such as:

• 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 suprachiasmatic nucleus in the hypothalamus, or "SCN") (3,4). In practice, the biological clock takes environmental factors into account. The amount of light, for example, plays a role in the production of the hormone melatonin, which creates a sleepy feeling. In the image below you can see 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 testosterone and the stress hormone cortisol, among other things, are influenced by the circadian rhythm (6). Testosterone is of course an important player in determining muscle strength and muscle mass. This applies especially to "free testosterone", testosterone that has 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 is anabolic and tells cells in muscles, among other things, to produce more protein so they grow.

Cortisol, by contrast, is catabolic and, under the influence of stress (literally "load"), causes the breakdown of muscle mass in favor of energy. However, it also increases your metabolism by burning fatty acids.

On the one hand, strength training causes your body to release more testosterone so that it can respond to the training by repairing the damage (deliberately caused) by training. On the other hand, more cortisol is also released because the body notices an increased need for energy and wants to meet that need.

Ultimately, it is therefore 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 increases in muscle strength (7). If this balance shifts in favor of cortisol, for example, this is often an indication of overtraining (8), although opinions on this continue to differ.

Base 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 evening and at night they are at their lowest (9). The increase in cortisol in the morning therefore causes, among other things, increased fat burning, but also protein breakdown in order to provide more glucose in the blood for daily activity (10). The reason for the increase in testosterone may be to limit the muscle-breaking effect of cortisol (11).

For some people this is a reason to do cardio mainly in the morning in order to benefit from the increased fat burning. For strength training, on the other hand, this seems to be a less suitable moment given the high degree of muscle breakdown caused by cortisol. Cortisol fluctuations show greater differences throughout the day than testosterone. Compared with 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). You can therefore imagine that there are other times of day when the T/C ratio looks somewhat more favorable for testosterone.

What is the best time for strength training?

Determining the best time for strength training based on testosterone levels seems very difficult. First, because cortisol peaks at the same time, but also because of personal differences. It has proven very difficult to establish the T/C ratio at different times and to find averages for it. Someone who gets up every day at 10:00 will probably have a different circadian rhythm than the baker who gets up at 04:00. These differences also exist in the extent to which hormone levels respond to training between experienced and inexperienced athletes, lean people and overweight people, and people of different ages. Testosterone levels throughout the day therefore do not seem to be the best steering instrument for determining the timing of your training, unless you could have your personal T/C ratios measured throughout the day. For people who are not preparing for the Olympic Games, that will be a step too far.

Despite changes in anabolism/catabolism being of great concern to weight-trained individuals, the T/C ratio is rarely reported in studies of circadian rhytms.

L. Hayes, University of the West of Scotland

As far as cortisol is concerned, despite what you might suspect, there is also no convincing research showing that it has an effect on strength during training. Nor are there studies that have been able to demonstrate a favorable time of training based on cortisol in the circadian rhythm:

Much literature concerns the catabolic effect of C in relation to overtraining; yet, no evidence documents a possible relationship between concentrations of C and strength or a time-of-day–specific adaptation to training related to C.

L. Hayes, University of the West of Scotland

And then we have not even talked about the influence of other hormones such as insulin, IGF-1 and growth hormone. The mutual cooperation and opposition of these hormones is so complex, dependent on so many variables and so different per person that it seems impossible to find a golden rule that lets you use them optimally to your advantage (naturally).

"Body temperature has the greatest effect on performance"

Body temperature also follows a circadian rhythm and peaks in the early evening (14, 15). As far as the biological processes in the circadian rhythm are concerned, body temperature seems to have the greatest influence on athletic performance (5). This is shown, among other things, by the fact that most world records have been achieved in the early evening (16). This can give a distorted picture because, for practical and commercial reasons, sporting events are often held in the early evening. In addition, the outside temperature is often higher around that time, especially in summer. On the other hand, studies have been carried out into an athlete's sporting performance at different times of day. These also show that the best results are usually achieved in the early evening (17). On average, the time at which performance is best (various criteria) lies between 15:30 and 20:30 (18). However, this also depends on which criterion is measured as "performance" and which type of subject participated (see below) (19).

An increased body temperature has many effects. The most important goal of a (general) warm-up, for example, is literally to raise the temperature. This activates the orthosympathetic part of the nervous system, which puts the body into an "action mode", as it were. Nerves work faster (20), joints move more smoothly through the production of synovial fluid, muscle strength increases (18), and blood vessels widen so that more blood, oxygen and building materials are transported toward the muscles (21).

Strength, endurance or flexibility?

It therefore does depend on what you mean by "performance". Are you concerned with (maximal/explosive) strength, endurance or flexibility?

For endurance capacity or "aerobic performance", for example, it is unclear whether this is influenced by the circadian rhythm. There are studies that confirm this, but just as many studies that contradict it. When it comes to strength and the effects of resistance training, however, all studies point in the same direction. Strength follows a clear circadian rhythm, even when you look separately at concentric, eccentric and isometric strength (22-25). When researchers specifically looked at the maximum force with which someone can contract the muscles, this also turned out to follow the same rhythm and to be positively influenced by body temperature (14).

Training consistently at the same time

Many people know the law of diminishing returns. Perhaps not by name, but certainly the consequences in practice. This principle means that your body responds less and less to the stimuli from training, and is therefore not really appreciated. However, it also has a positive side.

For example, the extent to which cortisol is elevated in the morning after training appears to decrease as people regularly train in the morning (24). The researchers who demonstrated this did take into account that this may be due to mental habituation to getting up early and anticipation of the early training. The mere knowledge that you are going to undertake a strenuous activity can already increase cortisol as a stress factor (26). The group of subjects who always trained in the morning had the best results in the morning during tests administered at different times of day. The researchers also saw that there was no difference in the increase in strength compared with people who trained at other times (24). The habituation was apparently enough to compensate for the disadvantages of the circadian rhythm. Other researchers had already concluded in 2005 that several weeks of consistently training in the morning can limit the influence of the circadian rhythm on athletic performance (26).

When to train?

It is very difficult to determine, based on various hormones such as testosterone and cortisol, when you could best train. In practice, however, the body appears to prefer the early evening, somewhere between 15:30 and 20:30. This is very likely due to the higher body temperature around that time.

As an athlete in a competitive setting, you would do well to train as much as possible at the time when competitions usually also take place. Through your body's habituation, you ensure that this becomes the time at which you perform best.

For most of us, unfortunately, it simply applies that we use the available moments to dive into the gym: one time in the evening after work, another time in the morning on a day off, and on the weekend in the early afternoon after sleeping in. In that case, do not overestimate the importance of training at a fixed time and simply use the opportunity you have to train.

References

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Other references:

• Chtourou H1, Driss T, Souissi S, Gam A, Chaouachi A, Souissi N.The effect of strength training at the same time of the day on the diurnal fluctuations of muscular anaerobic performances.J Strength Cond Res. 2012 Jan;26(1):217-25. doi: 10.1519/JSC.0b013e31821d5e8d.
• Winget CM, DeRoshia CW, Holley DC. Circadian rhythms and athletic performance. Med Sci Sports Exerc. 1985 Oct;17(5):498-516. Review.
• Reilly T, Atkinson G, Gregson W, Drust B, Forsyth J, Edwards B, Waterhouse J. Some chronobiological considerations related to physical exercise. Clin Ter. 2006 May-Jun;157(3):249-64. Review.
• Bird SP, Tarpenning KM. Influence of circadian time structure on acute hormonal responses to a single bout of heavy-resistance exercise in weight-trained men. Chronobiol Int. 2004 Jan;21(1):131-46.