Does It Matter What Time You Work Out?

If we've heard it once, we've heard it a thousand times: "Don't exercise before bed!" Conventional Internet wisdom holds that doing so is one of the great sins of both sleep hygiene and of exercise protocol. But why did anyone ever make this recommendation? As it turns out, exercising at night is basically just fine, and so you can and should exercise at whatever time of day works best for you.

After a workout, you may experience a spike in adrenaline — the fight or flight hormone — and feel "wound up." This is the basis of the recommendation: if you exercise in the morning or mid-day, you can put that energy and alertness to good use, but at night you'd assume it'd just make it difficult to sleep.

However, if you ask real-life people who really do exercise at night, the results are surprising. The National Sleep Foundation's 2013 "Sleep In America" study indicates that exercisers — even nighttime exercisers — sleep much better than non-exercisers, and they sleep better on days they exercised. Only 3 percent of the nighttime-specific exercisers report that they slept worse on their workout days.

These poll results corroborate a 2011 study in the Journal of Sleep Research that attempted to confirm or disconfirm whether the old don't-exercise-before-bed sleep hygiene tip had any scientific basis. Those researchers found that, according to sleep laboratory observations, "vigorous late-night exercise does not disturb sleep quality."

So, if you're not sleeping well, you might try switching your workout to earlier in the day just as an experiment (while you're at it, avoid these sleep-degrading foods too, and consider sleeping away from your partner). Otherwise there's nothing to worry about, and you can safely ignore the advice against exercising at night.