People usually train when they have time or when it fits with their schedule, letting their day-to-day life dictate when they hit the gym. However, muscular performance and hormone levels fluctuate throughout the day, which is completely normal but something to be aware of. Is there a way to workout on a certain time of day for peak performance and hormone levels? Hell yes there is.

The Regulator of Life: Circadian Rhythms

A circadian rhythm is an internal clock that controls all physiological processes of animals and humans. The circadian clock has several functions including control of your hormones and metabolism, organization of sleep/wake patterns and mental/physical performance.

The circadian adapts to environmental changes such as food intake, exercise and light/dark cycles. The system itself affects the regulation of nervous system activity and hormonal production, which in turn tells us when the optimal training time is. By fully understanding these processes, you will get a better idea of how the time of day may affect your training and results.

Both of these fluctuate throughout the day, peaking at certain times while being low at others. Here’s a depiction of the typical fluctuations of biochemical and physiological events with a 24-hour period, known as a biorhythm:

As you can see, fluctuations throughout the day may have an impact on our performance levels and influence the hormonal concentrations around training. Although some data suggests that training in the early evening may provide the greatest force and muscle strength, it’s not always as black and white as that.

Muscular Performance

Have you ever wondered why most sporting events are played in the afternoon, and why most world records are set in the mid-afternoon to evening? Studies in a variety of sports and activities – weightlifting, cycling, etc. – have shown measures of strength and power to be highest in the afternoon/evening compared to the morning. So, if you’re an elite athlete trying to win a competition or set some records, this time of day may help.

Optimal body temperature for training normally occurs during this time, providing you optimal nerve conduction velocity, joint mobility and safety, metabolism, and muscular blood flow. Your core body temp is low at night, rises quickly upon awakening, and reaches a maximum in the evening. Keep in mind that activities requiring strength and power have been shown to be more affected by time of day than other forms of activities, such as endurance events.

Hormonal Changes

The circadian rhythm also affects the fluctuations of your key hormones. The most important hormones related to training and body composition are testosterone, cortisol, and growth hormone. Testosterone is well known as a potent anabolic, muscle-building hormone. If we look at our testosterone levels throughout the day, in most cases, they’re highest in the morning and will drop throughout the day.

However, this normal rhythm can be altered depending on your lifestyle, sleep, and daily activity. One important consideration is that testosterone levels normally increase after exercise, and the rise in testosterone after exercise appears to be more profound in the evening than it is in the morning.

Growth hormone (GH) is another muscle building hormone. Normally, the majority of GH is released in “pulses” when you sleep, with the largest pulses occurring before midnight and some smaller pulses in the early morning. As with testosterone, intense exercise acutely elevates growth hormone levels, providing spikes post-workout and altering our body’s normal pattern at night.

In contrast, cortisol is a stress hormone with a bad reputation as it can cause muscle protein breakdown. While this is sometimes overplayed, cortisol does have some important roles. If cortisol is left elevated for some time it may have detrimental effects.

Our cortisol levels at rest follow a natural pattern, peaking in the morning and decreasing during the evening. Researchers have found the elevations of cortisol in response to exercise are lower in the early evening compared with the morning. In other words, if cortisol or other related factors such as recovery are an issue and you want to keep them under control, training in the morning may be best.

Theoretically, for maximal muscle growth, you’d want to have a high testosterone to cortisol ratio (muscle building vs. muscle breakdown). However, at this point in time the research is still controversial with regard to the relationship and effects of brief fluctuations in hormone concentrations on muscle growth.

So Is There Actually a Best Time to Train?

Only a few research studies have examined the relationship between training at different times and muscle growth. The most supportive evidence came from a 10-week training study where the subjects were assigned to either a morning (7-9 AM) or afternoon (5-7 PM) training group, both following the exact same training routine. Researchers found the afternoon group experienced a 3.5% increase in muscle size, versus 2.7% in the morning group.

So, while the trend is there, it failed to reach statistical significance. This may have been due to the timeframe (only 10 weeks, and muscle building is very slow) or amount of participants. Over 20, 30 or 40 weeks, these results may have been more noticeable, demonstrating a benefit for afternoon or evening training.

Lifestyle and Preference

Your preference is always an unappreciated yet vitally important aspect of diet or training. Far too often, people will make programming decisions based on what they believe to be “most optimal” at the cost of their own preference and lifestyle. For example, if training in the morning suits you better, is it best to disregard this and train in the evening for some form of hormonal and strength benefit?

The answer is no. Thinking logically, even if you were to get a 5% improvement in the evening, this would easily be countered by the fact you’re probably less motivated and tired after work. You may also have less energy and will have decreased performance, which probably leads to you doing less total volume. Hey, you want to get home, right?

These variables, particularly intensity and volume (total sets, reps, and weight lifted), are proven to be the most important aspects of training for muscle growth. To maximize your progress, pick your training time on these two key variables. Train when you can perform best and have an uninterrupted workout and plenty of time for volume.


You can see the same issues with dieting. For example, a complex strategy, which may increase fat loss by 5%, will often be very difficult to sustain. The plan will be much harder to stick to, be less enjoyable, and cause you to quit or be less consistent. Consistency is the number one factor, so reducing your chances of achieving this for a small boost is a recipe for disaster, whether it’s training or diet.

Pros vs. Average Joes

If you’re a pro athlete who trains and competes for a career, training in the PM could give you that 1-2% boost that makes the difference between winning a race and placing tenth. However, a lot more research is needed to draw solid conclusions.

For most people, the optimal time to train is when it best suits your lifestyle and when you know you can go into the gym with focus, motivation, and energy. For some, this is in the morning before work when your mind is clear and you can give 100% to your workout. For others, it may be in the PM. It simply depends on your own preferences.

Even though it may seem that there’s strong evidence for training in the mid-afternoon to evening to maximize performance and benefit from optimal hormone production, the evidence is far from conclusive. Ask yourself if it’s really that important when you may end up leaving early, losing intensity and focus or, worst of all, not being consistent. Remember, consistency trumps “optimal” when it comes to training and nutrition.