Studies on the impact of exercise on sleep are promising. They have shown (1) that it reduces sleep latency (amount of time it takes to fall asleep) and increases the quantity of slow-wave sleep (SWS), also known as deep sleep, which takes place during stage 3 (during which time it’s difficult to wake up). The brain is releasing low-frequency, high-amplitude delta waves that cause heart rate and respiration to slow down. The benefit here is for the functioning and restoration of our immune systems. (Fun fact: this is also when sleepwalking tends to happen.)
According to new research presented in March 2022 at the American Heart Association Conference, (2) resistance training may even have superior benefits on sleep than aerobic exercise.
Despite the consensus that exercise = good sleep, especially for those with insomnia (3) and Obstructive Sleep Apnea (OSA), (4) there are still lingering questions around what time of day is best to exercise. Although research shows (5) that moderate-intensity aerobic or resistance exercise does not compromise sleep as long as it stops at least 90 minutes prior to bedtime (so your core body temperature has time to return to pre-exercise levels), there are a multitude of factors that can dictate YOUR optimal time to exercise for the best sleep:
- Type of exercise
- Chronotype: natural patterns of when you prefer to sleep and when you have the most energy
- Age
- Underlying health conditions
High-intensity, aerobic exercise
It’s best to partake in high-intensity exercise in the morning or early afternoon so you avoid getting a flood of energizing endorphins immediately before bed.
Light exercise
Compared to vigorous exercise, a mind-body practice such as yoga, qigong, or tai chi can help you wind down at the conclusion of the day. Because it’s low-intensity, you’ll avoid getting your heart rate pumping, which increases core body temperature at a time when it should be dropping in preparation for sleep onset.
For the most part, chronotypes—which describe the times during which one has a natural propensity to sleep or be awake—are broken down into morning types (early birds, or larks) and evening types (night owls). The recommendations below are based on optimal skeletal muscle performance, but behaviorally if you are having trouble sleeping, there may be different timing recommendations to help with alertness.
Morning types
- Characteristics: An early riser with an early bedtime
- Recommended time of day to exercise: Morning (6)
Evening types
- Characteristics: Peak productivity begins mid-day, may have trouble waking up in the morning
- Recommended time of day to exercise: Evening (6)
In a 2017 study (7) with male collegiate soccer players, acute high intensity interval training (HIIT) in the evening negatively affected sleep quality for morning types but not for evening types.
High blood pressure
Research studies (8) indicate that, for those with high blood pressure, the best time to work out in order to sleep better may be the morning since cardio aerobic exercise earlier on causes a greater dip in nighttime blood pressure than afternoon workouts or evening exercise. Early morning workouts have also been linked to greater time spent in deep sleep for those with pre-hypertension.
Insomnia
In a four-month study (9) of older adults with chronic insomnia, researchers found that regular exercise significantly improved sleep quality while also reducing daytime sleepiness and depressive systems. In addition to sleep quality, improvements were seen in:
- Sleep latency
- Sleep duration
- Daytime dysfunction
- Sleep efficiency
- Depressive symptoms
- Daytime sleepiness
- Vitality/energy levels
To avoid sleep disruptions, those with insomnia should prioritize light-to-moderate exercise that takes place at least four hours prior to bedtime. (10)
Obstructive Sleep Apnea (OSA)
There have been many studies conducted on the beneficial relationship between exercise and Obstructive Sleep Apnea, with one meta-analysis (11) finding that physical activity reduced OSA severity by 32%, even without a significant decrease in body mass index (BMI), which is a contributing factor to OSA. Additionally, a randomized clinical trial (12) found that, after 12 weeks of moderate-intensity aerobic and resistance strength training, participants exercised a 25% reduction in OSA severity.
However, no research has been conducted on the timing of exercise for those with OSA, so it’s best to follow guidance by chronotype here.
READ MORE: When To See A Sleep Specialist: 6 Signs + Symptoms
One benefit of morning or early-afternoon workouts is that, depending on seasonality, they can be conducted outside with exposure to natural light, which is one of the most potent factors in regulating our 24-hour body clocks (aka circadian rhythms) to make it easier to fall asleep earlier at night.
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