Settling The Debate: AM vs. PM Workouts, Which One is More Beneficial?

The debate between morning and evening workout sessions and their claimed benefits has gone on for quite some time now. Some fitness enthusiasts and experts claim exercising in the early morning is the most optimal time. Others claim evening or late-night gym sessions are the most ideal for muscle gain and fat loss. Regardless of which side of the debate they may fall on, experts all agree that daily exercise is one of the best things you can do for your physical health. As health experts and fitness enthusiasts alike debate, lets examine the benefits of both morning and evening exercise.

Exercising regularly has a number of documented health benefits. From burning body fat and building muscle, to strengthening your bones and enhancing memory, exercising and moving your body routinely is a great way to improve your body’s overall health. In addition to some of the obvious aesthetic benefits, exercising regularly can also improve your mental health by reducing stress, boosting your confidence, and enhancing the quality of sleep you get at night. According to the Department of Health and Human Services, a healthy adult needs at least 150 minutes to 300 minutes of moderate aerobic activity per week (such as brisk walking) or 75 minutes to 150 minutes a week of vigorous-intensity aerobic activity (like swimming, running, or hiking), in order to maintain a health lifestyle. But is there an optimal time of day to get your sweat on? That is the question that scientists have recently set out to find an answer to.

A team of international scientists at the Helmholtz Zentrum Munchen German Research Center for Environmental Health recently conducted a study examining the effects of exercise on the cells of mice in the morning and in the evening. Blood samples and different tissues samples, including heart, brain, muscle, liver, and fat were collected and analyzed by mass spectrometry. This enabled them to analyze hundreds of different hormone and metabolite signaling molecules in each tissue and monitor any molecular changes that occurred in the tissue at different points in the day. The study found that different tissues responded positively to exercise dependent on the circadian rhythm of the test subjects. Due to mice being typically nocturnal animals, most of the hormonal and metabolic activity within each tissue occurred when they were given exercise at night. However, it is important to note that humans on possess a different circadian rhythm than mice and are not nocturnal by nature (despite what your college roommate may have had you believe).

So how does exercise effect the human body at different points in the day? Well according to a study conducted by researchers at the United Kingdom’s prestigious Bath University, the average person reaches their prime window for physical activity at some point early in the morning. This is due to the natural increase in testosterone our bodies experience during the early part of the day. Testosterone fuels your energy levels and muscle gains and is produced in the morning at a rate that is one third higher than in the evening. Optimizing your muscle growth and similarly doubling your fat-burning potential when hitting the gym early in the morning. Additionally, researchers discovered that subjects who exercised in the morning tended to eat an average of 100-200 less calories throughout the day than their night owl counterparts.

All of this being said, there are some benefits to working out in the evening. For example, your muscles gradually become more flexible as the day goes on and your anaerobic capacity (used for big lifts) is approximately seven per cent higher in the evening. Increased flexibility and anaerobic capacity can lead to better performance and decreased risk of injury, especially in regards to strength training exercises. According to the Journal of Clinical Endocrinology & Metabolism, protein absorption is also better in the evening than in the morning or early afternoon. Increased protein absorption can help your muscles grow more and speed up their recovery.

Although evening workouts have proven to possess their own health benefits, they still fall short compared to morning exercise. Early morning workouts still show the most optimal fat-burning and cognitive benefits in comparison to late afternoon or night time exercise sessions. That said, most health and fitness experts maintain that the most important factor in any exercise routine is consistency. For some this may mean getting their workout over with early in the morning, for others this may mean going at night after they have completed their work for the day. All-in-all finding a fitness schedule that enables you to stay consistent is the most important way to ensure you are getting the most out of your workout.


1. Helmholtz Zentrum München – German Research Center for Environmental Health. Scientists dive deep into the different effects of morning and evening exercise. ScienceDaily. ScienceDaily, 13 January 2022.

2. Cooper, E., Ling, T., & Lane, E. (2021, June 29). Should I work out in the morning or the evening? here’s the latest science. Men’s Health. Retrieved January 19, 2022, from

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