Scientists say exercising at different times can benefit the body in different ways because of circadian rhythm, and can even help to fix a faulty body clock

Exercise at any time is beneficial in improving health, but recent research has demonstrated that exercise benefits the body in different ways, depending on the time of day.

The body produces different health-promoting signalling molecules in an organ-specific manner following exercise depending on the time of day, these signals then have a broad impact on health, influencing sleep, memory, exercise performance, and metabolic homeostasis.

Other research suggests that muscle strength, flexibility, power output and endurance are better in the evening than in the morning, and that people who exercise in the evening can take up to 20% longer to reach the point of exhaustion.

Using the circadian rhythm, where almost all cells regulate their biological processes over 24 hours, the sensitivity of different tissues to the effects of exercise changes depending on the time of day. Other research has formerly confirmed that exercise timing according to our circadian rhythm can optimize the health-promoting effects of exercise.

However, scientists still do not know why exercise timing produces different effects, so to gain a better understanding, an international team of scientists recently carried out a study of exercise performed at different times of the day.

Professor Juleen R. Zierath from Karolinska Institutet and the Novo Nordisk Foundation Centre for Basic Metabolic Research (CBMR) at the University of Copenhagen, said: “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.”

Different times of day influence skeletal muscle metabolic pathways and endurance capacity

In the most comprehensive study to date, published in the journal Cell Metabolism, the researchers carried out a range of experiments on mice that exercised either in the early morning or the late evening.

Blood samples and different tissues, including brain, heart, muscle, liver, and fat were collected and examined by mass spectrometry. Scientists were able to detect hundreds of different metabolites and hormone signalling molecules in each tissue, monitoring how they were changed by exercising at different times of the day.

This new research introduces a better understanding of how tissues communicate with each other, and how exercise can help to ‘realign’ faulty circadian rhythms in specific tissues – often, faulty circadian clocks have been linked to increased risks of obesity and type 2 diabetes. The study identified new exercise-induced signalling molecules in multiple tissues, requiring further investigation to understand how they can individually or collectively influence health.

Dominik Lutter, Head of Computational Discovery Research from the Helmholtz Diabetes Centre at Helmholtz Munich, added: “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.”

Associate Professor Jonas Thue Treebak from CBMR at the University of Copenhagen, and co-first author of the publication, said: “Not only do we show how different tissues respond to exercise at different times of the day, but we also propose how these responses are connected to induce an orchestrated adaptation that controls systemic energy homeostasis.”

Beneficial for exercise research and its impact on health

 However, the study has its limitations, as the experiments were carried out in mice. While mice share many common genetic, physiological, and behavioural characteristics with humans, they also have important differences. An example of this is that mice are nocturnal, and the type of exercise was also limited to treadmill running, which can produce different results compared to high-intensity exercise.

Additionally, the impact of sex, age and disease were not considered in the analysis, but this study stresses the utility of the exercise atlas developed as a comprehensive resource for exercise biologists.

Assistant Professor Shogo Sato from the Department of Biology and the Centre for Biological Clocks Research at Texas A&M University, and fellow co-first author, stated: “Despite the limitations, it’s an important study that helps to direct further research that can help us better understand how exercise, if timed correctly, can help to improve health.”

Fellow co-first author Kenneth Dyar, Head of Metabolic Physiology from the Helmholtz Diabetes Centre at Helmholtz Munich, said: “While our resource provides important new perspectives about energy metabolites and known signalling molecules, this is just the tip of the iceberg. We show some examples of how our data can be mined to identify new tissue and time-specific signalling molecules.”

 Read the full study here.


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