Determining the Best Time to Work Out
Most people don’t think to ask what the best time to work out is, except inasmuch as there’s a time of day that fits their schedule best.
To the extent that the question does get asked, popular wisdom holds that first thing in the morning is the best time to work out because you’ll burn more fat on an empty stomach.
However, the research doesn’t entirely support that. In fact, when it comes to weight training, a growing body of research suggests that evening training is more productive, while the evidence on cardio is a bit more muddled.
What the Research Says About the Best Time to Work Out
Studies have not consistently shown that training in the morning causes more weight loss or better performance over the long term. In fact, while the evidence is equivocal with regards to aerobic exercise, when it comes to resistance training, trainees perform better later in the day.
A 2014 study by Malhotra et al found significantly greater strength gains from early evening versus morning training. The difference was around 25 percent for eccentric (lowering the weight) vs 10 percent for concentric (raising the weight) exercise.
Related: Will Creatine Amplify Your Training?
A 2016 study tested training in the morning between 6:30 and 10 a.m. against training in the later afternoon or early evening between 4:30 and 8 p.m. While the difference in strength gains fell short of statistical significance, the evening training group did gain significantly more muscle mass.
The effects may be more pronounced the more advanced the trainee is. Another study performed on bodybuilders found that the evening group gained 3.2 percent fat-free mass, and lost four percent body fat, while the morning group gained only 0.6 percent fat-free mass and gained five percent body fat. While none of the results were statistically significant due to the small sample size, they are in line with the results of other studies.
In general, studies on resistance training by experienced trainees either find evening training to be superior or find no significant difference between morning and evening, but they rarely if ever find morning training to be superior. This is may be because muscle anabolic signaling is stronger later in the day.
The story for cardio is a bit different. As mentioned above, studies do not consistently find time-of-day effects for cardio, at least in terms of performance or long-term energy expenditure. Fasted cardio does burn more fat as you’re doing it, but only because it burns less glycogen – more fat burning at the time you work out doesn’t necessarily mean more fat loss in the long run.
However, at least some studies do support that doing cardio early in the morning – and perhaps while fasted – can get better results. It may actually be that this has more to do with the appetite-suppressing effects of exercise than with the exercise burning off more energy.
It’s also worth noting that there is an interference effect between cardio and resistance training. Since one way to reduce that interference effect is to separate the two, it may be worth doing cardio in the morning just to avoid sabotaging your weight sessions later in the day.
Why It’s Better to Lift in The Afternoon: Three Theories
Unlike the evidence for morning cardio, the evidence showing that it’s better to weight train later in the day hasn’t yet been fully explained. Why would you build so much more muscle just from training a few hours later? There are three likely reasons.
First, your hormonal environment is more favorable later in the day. Testosterone peaks at night, while cortisol peaks in the morning. Since a high testosterone/cortisol ratio has been shown to correlate with greater recovery capacity and muscular hypertrophy, this could mean that you’re better off training when that ratio is high.
Second, core body temperature is higher later in the day. In fact, it peaks in the evening, around seven or eight. Why is that important? Core body temperature has shown to correlate with exercise performance.
It has also been observed that most sports records are broken in the early evening, and this has been demonstrated to correlate with peaks in core body temperature.
Third, working out later in the day means you go to sleep sooner after your workout. Since sleep is crucial to muscular recovery and growth, sleeping sooner rather than later may be beneficial.
Of course, there’s also a post-workout refeeding window in which your muscles are better able to utilize protein and calories to rebuild. As such, you probably don’t want to go to sleep right after your workout. The later afternoon and early evening may then be a good compromise between sleep and refeeding, allowing you to eat one or two good meals and still get to sleep fairly early on in the recovery process.
When Training Later in the Day Is Not the Best Time to Work Out
There are a few cases where you may still be better off training earlier in the day.
First, that might be the only time of day when you have time. Maybe. Be honest about whether that’s literally true though, or you just don’t want to train at a different time.
More crucially though, some people with high-stress jobs may suffer from training later in the day. At least one study shows that shift workers reach peak performance earlier in the day.
If you are extremely tired and stressed out after work, you may still be better off training at lunch or even in the morning. In this case, 100 mg of caffeine can help raise your energy level and core body temperature to make up some of the loss from training at a less than optimal time.
Your body will also become entrained to the time of day that you work out, so whatever time you choose, stick with it and train at that time (give or take an hour) with perfect consistency.
While early morning may indeed be the best time for cardio, weight training is better done later in the day. By separating the two and doing a theme each at their optimal time, you can build more muscle and lose more fat, all while enjoying relatively less fatigue.