Is working out before bed bad for your nighttime rest? Can evening exercise lead to insomnia? Is there an optimal time of day to work out? Get-Fit Guy answers your questions.
In a previous Get-Fit Guy article, What’s the Best Time of Day to Work Out?”, I answered a listener question about whether working out earlier in the day would somehow boost your metabolism or be better for fat loss as compared to exercising later in the day.
In my response, I explained that while it certainly is true that morning exercise can jumpstart your metabolism and calorie-burning (especially compared to sitting at the breakfast table for an extra 30 minutes), it may not be the best time to do high intensity intervals or weight training, for two reasons:
Your body temperature peaks in the afternoon, usually between 2pm and 6pm, which means that you’re going to be able to do hard workouts even harder around this time. This could result in a bigger fitness boost, which is a bonus if your goal is getting significantly fitter, bigger, faster, stronger, or more powerful.
Your protein synthesis, or ability to use dietary amino acids for muscle repair, also peaks later in the day—in the early evening between 5pm and 7pm. So if you’re finishing up a hard workout around that time of day, you’ll also maximize recovery. This also backs up the idea that later afternoon or early evening is the best time of day for more difficult workouts.
However, when you wake up in the morning, your liver’s carbohydrate stores are relatively empty, so an easy walk, light jog, yoga class, or bout of cardio can help to mobilize fatty acid stores, circulate blood and lymph fluid, and increase the activity of fat burning enzymes. So the morning is a good time of day for easy, aerobic “fasted cardio.”
This is why, whenever possible, I begin each day with a light, easy bout of physical activity. For me, this includes about 5 minutes of calisthenics (jumping jacks, push-ups, air squats, etc.) and about 10 minutes of light yoga, before breakfast. Then, time permitting, I include a hard, late afternoon or early evening workout with intense cardio and/or weight training.
How Late Is too Late to Work Out?
But when it comes to that harder afternoon or early evening session, how late is too late to work out? Should you work out before bed, or will it disrupt your sleep?
It turns out that Dr. Stuart Quan, a professor of sleep medicine at Harvard Medical School, has investigated this very question. In a recent CNN report, he points out that there is anecdotal evidence that some people have difficulty falling asleep after vigorous bouts of late-night exercise, and that because of high adrenaline, increased brain activity, and a difficulty “winding down,” these individuals in particular should be wary of working out too close to bedtime.
Dr. Quan recommends that if you fall into that group, you give yourself a few hours between your workout time and bed time to allow your body temperature to cool down to 98.60, your heart rate to return to its resting pace, and your adrenaline levels to lower.