You may already have some idea that exercise can affect the body differently according to the time of day. Like many, you may even have been told that it’s better to exercise in early evening, because later in the day the ratio of cortisol to testosterone becomes more favourable to building muscle.

Well, you’d certainly be right that the time of day can make a difference to the effects of exercise, and a new study out of the German Research Center for Environmental Health is showing just how big of a difference it can make.

The research, carried out on mice, shows that the body produces different health-promoting signaling molecules in an organ-specific manner following exercise at different times of day. These signals have a broad impact on health, and influence sleep, memory, exercise performance, and metabolic homeostasis.

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Are you a morning or an evening person? The effect of exercise at different times of day

“A better understanding of how exercise affects the body at different times of day might help us to maximize the benefits of exercise for people at risk of diseases, such as obesity and type 2 diabetes,” says Professor Juleen R. Zierath from Karolinska Institutet and the Novo Nordisk Foundation Center for Basic Metabolic Research (CBMR) at the University of Copenhagen.

The biological processes of almost all cells are regulated over a period of 24 hours, otherwise known as a circadian rhythm. in simple terms, this means that the different tissues are more or less sensitive to the effects of exercise depending on the time of day.

The researchers were building on earlier research which confirmed that exercise timing according to the body’s circadian rhythms can enhance the health-promoting effects of exercise.

The scientists wanted a more detailed understanding of this effect, so they conducted a variety of experiments on mice that exercised either in the early morning or the late evening.

The took blood and tissue samples, including brain, heart, muscle, liver, and fat, and then analyzed them using mass spectrometry. This allowed the scientists to identify hundreds of different metabolites and hormone signaling molecules in each tissue, and to monitor how they were changed by exercising at different times of the day.

The result is what the researchers call an ‘Atlas of Exercise Metabolism’, a map of exercise-induced signaling molecules present in different tissues following exercise at different times of day.


Training to failure appears to confer no extra benefits, fascinating meta-study

training to failure

To train to failure or not to train to failure? That is the question – or, at least, it’s one of a number of questions that get asked again and again about weight training.

A meta-study from 2021 may finally settle the interminable debate, however.

Researchers gathered together 15 previously published studies for their own study and concluded that there appears to be no noticeable difference between training to failure and not.


“As this is the first comprehensive study that summarizes time and exercise dependent metabolism over multiple tissues, it is of great value to generate and refine systemic models for metabolism and organ crosstalk,” adds Dominik Lutter, Head of Computational Discovery Research from the Helmholtz Diabetes Center at Helmholtz Munich.

Among the new insights are an increased understanding of how tissues communicate with one another, as well as how exercise can restore faulty circadian rhythms. Faulty circadian rhythms have been linked to increased risks of chronic diseases like obesity and type 2 diabetes.

The study also identified new signaling molecules produced by exercise in a number of different tissues. In time, these will be further investigated, to understand how they affect health, individually and in concert.

Although the study has limitations – it was carried out in mice, and sex, age and disease were not considered as factors – the authors are confident that the research will lead to further studies that will help illuminate how exercise can be timed to maximize its beneficial effects.

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