Millions of Americans take time out of their busy schedules to exercise daily. But only 23% of adults aged 18 and older meet the recommended guidelines for aerobic and muscle-strengthening activities. The biggest obstacle for most people: not having enough time. On the contrary, says a 2019 CDC and Rand study. Surveying more than 30,000 participants, the study found that Americans on average have more than five hours of free time per day.
Whether you’re considering starting a training program or you’re a more experienced athlete, one of the biggest questions I hear is, “When is the best time to exercise?” Most people are quite regimented and protective when exercising. Choosing to exercise in the morning or evening is often the result of a work schedule or childcare responsibilities. Or simply if one is a “morning person” or a “night owl”.
But is there any science to support training in the morning versus training in the evening? A recent study published in Frontiers in Physiology has provided some insight.
Are you next? More Americans than ever are being diagnosed with high blood pressure.
After:Are you at risk of a heart attack during your workout?
Early bird gets the exercise worm?
This was a relatively small study from Skidmore University that collected data from 27 women and 20 men who were already very active with a regular exercise regimen. Participants were followed for 12 weeks. They did one of four different exercise routines – stretching, resistance training, interval sprints or endurance training – four times a week for an hour each time. One group did the routine between 6:30 a.m. and 8:30 a.m. and the other group between 6 p.m. and 8 p.m.
For the group that trained in the morning:
- Women had 7% greater abdominal fat loss, greater reduction in blood pressure and greater leg strength
For the group that trained in the evening:
- Women had greater increases in upper body strength, power and endurance and improved mood
- The men had improved heart health, metabolic health and emotional well-being
- Men also had greater weight loss and lower blood pressure
Dive deeper into other research
Previous studies that looked at the effects of exercise over time were not broadly consistent with the results of this new study. In contrast, a small 2019 study found that men also lost more weight if they exercised in the morning. But several previous studies support the current study’s finding of improved metabolic health in men who exercised in the afternoon, including better insulin sensitivity and better heart rate control. blood sugar.
An international consortium of researchers carried out a fascinating research study in January 2022 that looked at the molecular changes occurring in cells of several organs in mice to try to quantify at the most basic cellular level what happens when exercise is done in the morning compared to the evening. . Molecular profiles in mice showed a greater reliance on fat to fuel morning exercise and a greater reliance on glucose to fuel afternoon workouts. While some might argue that we cannot extrapolate data from mice to humans, the cellular processes at the molecular level are similar.
Does TikTok’s ‘grenade pump’ actually work? the answer might surprise you
On social media, people are drinking a gallon a day… How much water do you really need?
Other factors believed to play a role include sleep quality and hormones.
The role of sleep
One possible explanation is that women tend to spend more time in the deep sleep phase and therefore tend to be more alert and ready to exercise earlier in the morning. But there are plenty of men who also prefer to exercise in the morning. This brings us to one of the biggest sleep and exercise myths; that exercising too late in the evening or close to bedtime will lead to reduced quality of sleep. Again, it depends. Exercising late in the day might not affect these self-proclaimed night owls. Importantly, a meta-analysis identified 29 studies that demonstrated that exercise improved sleep quality or duration.
Don’t count hormones
Levels of cortisol, the stress hormone, are highest in both men and women in the morning. This could generate a need to “burn” stress for men and women who prefer to do cardio type workouts earlier in the morning. Cortisol, however, can have an inhibitory or catabolic effect on muscle building. So, men and women whose goal is strength training might see greater benefits with evening workouts.
It’s also worth mentioning that the latest study found that macronutrient intake didn’t play a role. Study participants also had to stick to the exact same diet of hearty meals a day at the same times for 12 weeks.
The ‘X’ factor: do you
Conclusion: This was a small study and we still don’t know a lot about the benefits of exercise over time. This adds to the body of evidence that metabolic benefits are greater for men who exercise in the evening. For women whose goal is to burn fat, this study showed a clear benefit to a morning workout. And I think we can’t ignore the catabolic effects of cortisol; for men and women whose goal is to build strength, an evening workout might be best.
Whether you exercise in the morning or in the evening, the main thing is that you exercise and you certainly reap the many benefits. If you feel better mentally and enjoy working out first thing in the morning, then stick with it! If you have a specific goal in mind, consider the results of studies to choose your time of day to train.
Can daily coffee consumption increase your life expectancy? Here’s what the latest research says
Michael Daignault, MD, is a Los Angeles Board Certified Emergency Physician. He studied global health at Georgetown University and holds a medical degree from Ben Gurion University. He completed his emergency medicine residency at Lincoln Medical Center in the South Bronx. He is also a former United States Peace Corps volunteer. Find him on Instagram @dr.daignault