We have been debating for years whether it is better to go to the gym in the morning or in the afternoon. Physiology finally has the answer

In the world of sports there is an eternal debate about the best time to exercise. On the one hand, there are those who defend tooth and nail that get up early to train At six in the morning it activates the metabolism for the rest of the day. On the other hand, there are those who claim that the body only performs at its maximum after leaving work late in the day.

Who is right? The answer, as is often the case in exercise physiology, has different nuances, since if we turn to scientific literature, recent studies and controlled trials, we will discover that the best schedule depends on the biology, objectives and internal clock of each athlete.

And something that is already known is that our biology does not function in a flat manner during the day, but is governed by circadian rhythms. Here, science already indicates that body temperature and neuromuscular performance reach their maximum peak in the afternoon, generally between 5:00 p.m. and 7:00 p.m. Although the key here is whether this can translate into more muscle in the long term.

The concrete studies. In 2019, a group of scientists public a meta-analysis that confirmed that, indeed, baseline muscle strength is greater in the afternoon. However, for early risers, they also pointed out that, if consistency is maintained at the same schedule, the long-term gains in strength and muscle mass are similar, regardless of the schedule, because the human body ends up adapting to what is asked of it.

But there is a fairly clear exception, as stated in a study published in 2016. Here, after 24 weeks follow-upit was shown that there is a greater gain in muscle mass in the legs if training is done in combination of bodybuilding and weights.

The morning situation. If the goal you have set is not to lift the maximum weight possible, but rather to improve cardiovascular health or combat insulin resistance, the balance tips towards the morning, as confirmed by a study published in 2024 that analyzed patients with metabolic syndrome who performed intense aerobic exercise.

Here it was seen that training in the morning achieved a reduction in systolic blood pressure of 4% compared to only 1% in the afternoon group. Additionally, the early risers group experienced a 14% improvement in insulin resistance, compared to 4% for the evening group. Furthermore, narrative reviews suggest that morning exercise helps advance sleep phases and improve the lipid profile.

It depends on each person. But beyond what the population averages say, we must take into account the genetic and behavioral component of each person, and above all their chronotype. In this way, people who get up early naturally perform better in the morning, while those who perform better at night, if they are forced to train at six in the morning, the truth is that they will have greater fatigue and a worse perception of effort.

The conclusion. Although science finds specific metabolic benefits in the morning and performance peaks in the afternoon, general reviews agree on an insurmountable rule of thumb: the best time to train is the one in which you can maintain long-term adherence. The hormonal peak in the afternoon is of no use if your work obligations prevent you from going to the gym regularly or it means a great sacrifice to radically change the routine you are following.

Images | Drazen Zigic

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