I can honestly say I have never heard anyone say to me, “I think I’m getting too much sleep, do you know any ways to help me cut back?” Usually it’s the exact opposite. These days everyone seems to be tired, all the time. Almost everyone is looking for ways to get more sleep, to go to sleep faster, stay asleep longer, have more restful sleep and feel more awake and alert during the day. Millions if not billions of dollars have been poured into sleep-aids including prescription drugs, noise machines, matresses and so on. But could the answer to a better nights sleep be in how you spend your day?
Sleep is a restorative process and the different stages of sleep perform different roles in the restoration of our bodies.Exercise has an effect on certain stages of sleep so let’s start by taking taking a look at what each stage of sleep looks like and what your body is doing during each stage.
Stages of Sleep
There are 5 stages of sleep that we cycle through during the night. The first four stages are non-rapid eye movement sleep (NREM) and the last stage is rapid eye movement sleep (REM). About 50% of adult total sleep time is spent in stage 2 sleep, 20% in REM, and 30% in the other stages. A complete sleep cycle generally lasts 90-110 minutes with increasing REM periods and decreasing deep sleep periods as the night progresses.
Non-REM Sleep
Stage 1: Light sleep; easily awakened, eye and muscle activity slows; may experience feelings of falling.
Stage 2: Eye movements and brain waves slower; occasional bursts of rapid brain waves; breathing an heart rate regular; body temperature drops.
Stages 3 & 4: Deep sleep; difficult to wake; no eye movement or muscle activity; bedwetting, night terrors or sleepwalking may occur; very slow, delta brain waves; few small faster waves; groggy or disoriented if awakened during this stage.
- Blood pressure drops
- Heart rate and respiratory rate slow
- Muscles relax; blood supply to muscles increases
- Tissue growth and repair occurs
- Hormones released (such as growth hormone which is necessary for proper growth and development)
REM Sleep
- 70-90 minutes after sleep onset; eyes dart back and forth; body immoble (paralyzed) and relaxed; breathing rate, heart rate and blood pressure are irregular
- Provides energy to brain and body
- Supports daytime performance
- Brain is active and dreams occur
Benefits of Adequate Sleep (National Heart, Lung and Blood Institute)
As adapted from ACSM’s Health and Fitness Journal, Sept/Oct 2013.
1. The decrease in both heart rate and blood pressure during NREM sleep appear to promote cardiovascular health. Without adequate sleep the beneficial drop in blood pressure may not occur.
2. Learning or remembering are done better after a good night’s sleep. Lack of sleep can make it harder to focus, lead to confusion and faulty decisions and slow reaction time.
3. Growth hormone released during stage 3 of the sleep cycle promotes the repair of cells and tissue.
4. The immune system receives a boost during sleep as the body releases cytokines reponsible for targeting infections.
5. Appetite control is aided by increases in leptin (appetite supressor) and decreases in ghrelin (appetite stimulator) during sleep.
Effects of Exercise on Sleep
The National Sleep Foundation cites regular exercise as one of the top ten tips for healthy sleep. Though findings on timing, type, and intensity of the exercise are debated, experts seem to agree that some exercise is better than no exercise at all when it comes to sleep. Some of the benefits ofchronic exercise on sleep include:
- Shorter sleep onset latency
- Less time awake after sleep onset
- Longer total sleep time (studies show increases in stage 2, light, sleep and no changes in the length of REM sleep)
- Improvements in sleep quality in adults > 40 years with regular aerobic and resistance training.
- perceived reduction in time to fall asleep
- reduced use of medicaiton for insomnia
Exercise is thought to improve sleep by a few mechanisms including anxiety reduction, antidepressant effects and thermogenic effects (body heat accumulates during exercise and then drops more rapidly at sleep onset). Ideally exercise is thought to be most effective in aiding sleep when performed 5-6 hours before bedtime.
The National Sleep Foundation also found the following results in their 2013 poll:
- All respondents, regardless of activity level reported similar to average sleep length as well as reporting needing about the same amount of sleep. Perception of sleep quality was higher in exercisers than nonexercisers for both workdays and nonworkdays.
- Vigorous exercisers generally reported the best sleep and reported fewer sleep problems.
- About half of respondents (regardless of activity level) indicate their physical activity was less than usual after a night of little to poor sleep.
- Those who spent less time sitting tended to report better health and better sleep quality.
- Exercisers who reported moderate and/or vigorous activity within 4 hours of bedtime reported similar sleep and sleep quality compared to those who exercised mor than 4 hours before bedtime.
Overall, exercise is seen by experts as beneficial to sleep, even though the details may be debatable. Remember, the cycle will feed itself once you find a routine and stick to it; as you exercise more, you will sleep better and when you sleep better you will be less fatigued and more able to spend energy on exercise.
Worried you are not getting enough sleep? Take the Epworth Sleepiness Test here to see if you should talk to your doctor: http://www.sleepfoundation.org/sleep-scale.
Bushman, Barbara. Exercise and Sleep. ACSM’s Health and Fitness Journal. Vol 17/No. 5. September/October 2013.
National Institute of Neurological Disorders and Stroke. “Brain Basics: Understanding Sleep.” http://www.ninds.nih.gov/disorders/brain_basics/understanding_sleep.htm. 21 May 2007.
National Sleep Foundation. “What Happens When You Sleep?” http://www.sleepfoundation.org/article/how-sleep-works/what-happens-when-you-sleep. 30 Sep 2013.
National Sleep Foundation. www.sleepfoundation.org/2013poll
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