In many things in life, timing is everything. When it comes to your body, there’s even a science—chronobiology—dedicated to the study of how our internal clocks work, and the effect of time of day on physiological and mental performance. Much research has tried to pinpoint exactly when within 24 hours we’re at our strongest, fastest, and most flexible. The surprise: In all of these cases, 5pm may be the happiest hour. That’s when your body temperature is at its peak if you normally wake at 7am and sleep at 11pm, says Roberto Refinetti, Ph.D., editor-in-chief of the Journal of Circadian Rhythms. (Though if your sleep schedule is different, you should shift that forward or back based on your normal rising time.) Early evening is also when blood pressure and heart rate are lowest, other optimal conditions for performance. In fact, afternoon and early evening is the time of day when personal bests and even world records are most likely to be set.
That said, there’s been some compelling research for why you might exercise, eat, or even sleep at other times of day, based on your goals. But not to worry if you can’t set your schedule based on the science—after all, at the end of the day, getting your workout in at all is way more important than when exactly you do it. Here, the best time of day...
...for Weight Loss
Any extra calorie burning at any time of day is going to be beneficial, particularly if you spend the lion’s share of your hours sitting on your duff. That said, there’s some compelling evidence that morning pre-breakfast “fasted” workouts (in which you haven’t eaten since dinnertime) may burn more fat and curb your appetite all day long. You may also benefit from limiting your window of eating to your most active eight hours of the day, which some research suggests may help control body weight.
...to Build Muscle
If your aim is hypertrophy, a mid-morning pump session could be the secret to muscle growth. That’s when blood testosterone levels are at their highest. Can’t hit the gym until later in the day? Not to worry: Muscular strength peaks in the early evening, so you may be able to rack up even more plates if you hit the gym right after work. Whenever you get it in, research suggests that a pre- and post-workout snack of around 30 grams of protein each, may have the greatest effect on muscle gains.
...to Go for a Run
When you’re training for a race, the name of the game is adaptation. For this reason, it’s best to schedule the majority of your training runs at the same time of day you’ll be running the race. Since most competitions happen first thing in the morning, you may be in for some early wake-up calls. For very long runs of more than an hour, sports drinks or gels during and after the workout can help prevent “bonking” (running out of stored glucose.)
...for High-Intensity Workouts
Again, late afternoon is king when it comes to eliciting your max performance. However, given the body’s propensity for adaptation, if you want to be consistent about hitting it hard in the morning, you may be able to match your performance level. Again, if you’ll be going long and hard, keep up your energy by sipping on electrolyte beverages, and follow up your session with a balanced meal of protein, carbs, and fat.
..for a Stretch Session
Your body may react most favorably to static stretching, foam rolling, or yoga toward the end of the day, when body temperature is high and muscles are the most supple. A little pre-bed stretching can also erase tension from your day. Make it a habit, and your body will develop a new relaxation routine to signal it’s time for some shuteye.
...to Go to Bed
Anyone looking to make changes in their fitness knows that quality sleep is essential to muscle rebuilding and recovery. But it may not be how much sleep but when the sleep happens that matters most. A new study suggests that inconsistent or shifting bedtimes can affect the quality of shuteye, making it less restorative, even if the amount of sleep is the same. So do yourself a favor, especially when in heavy training: Hit the sack at the same time every night.