Physical exercise and insomnia
Exercise is a well-known mechanism for reducing insomnia. However it is a double sided condition. When done correctly it will reduce insomnia. When done incorrectly it will increase insomnia. The most important factor here is the timing, where exercising should be finished at least 3 hours before going to sleep. This means exercising in the morning, afternoon or early evening.
Let’s look at why this is the case.
When you exercise several things happen.
- Body temperature increases
- Adrenaline levels increase
- Heart, brain and muscles are stimulated
- Cardiovascular activity and blood flow are stimulated
- Endorphin levels increase
- Regulation of cortisol (hydrocortisone) levels is improved
Of course exercise affects many other things, however the list above includes the most significant changes, particularly as relevant to sleep.
Analyzing these effects determines:
Body temperature
Falling asleep is easiest when body temperature is low. This generally means falling asleep right after exercise will be more difficult than normal. On the other hand if you allow yourself 3 or more hours to cool down after you’ve exercised, the cooling down of your body will actually help you fall asleep.
Adrenaline
Adrenaline is a hormone that stimulates blood flow to increase oxygen to the muscles and brain, which allows for increased physical and mental activity. This is useful for exercise but negatively affects sleep. As with body temperature, it is therefore best to wait for a period of at least 3 hours before sleep to allow the level of adrenaline to return to normal.
Heart, brain and muscle stimulation
Proper exercising stimulates the heart, brain and muscles in a positive manner. The heart is stimulated to pump more blood, which improves cardiovascular development. Increased blood flow to the brain stimulates new nerve cell development and synaptic activity. Increased blood flow to the muscles aids in increased muscle performance as well as muscle growth. How does this affect sleep? Sleep is the period when the body does most of its repairs, meaning that after exercise the body is prepared to sleep well in order to achieve these repairs.
Endorphin production
In order to counteract the mild level of pain caused by exercising, the body creates natural pain killers called endorphins, which are similar to morphine except non-addictive. Endorphins also act as sedatives, which have the effect of reducing stress. The release of endorphins happens about 30 minutes after physical activity starts and is experienced as a mildly euphoric sensation that impacts positively on self-esteem and well-being. These positive feelings can last up to 12 hours.
As related to sleep, the sedative effects of endorphins relax the mind and induce sleepiness. However this is only beneficial after the initial endorphin “rush” (euphoria) has had some time to subside. Considered with body temperature and adrenaline levels, this means allowing for at least 3 hours before bedtime.
Cortisol regulation
Cortisol (hydrocortisone) is a hormone that is released by the adrenal gland as a way to wake up the body and mind. It functions to increase the availability of fuels for the body in preparation for increased physical and mental activity. Normal cortisol release happens on a daily cycle that is highest in the morning when we wake up and lowest in the evening before we sleep. When its regulation is out of balance, usually due to mental stress, its effects are magnified, and include:
- processes that allow for increased access to glucose
- increased calcium levels in the blood flow
- which lowers available calcium for bone development
- inhibiting the pathways that release sex hormones
- which lowers the sex drive
- a lowering of the immune system
- which increases risk to disease and infection
- a decrease in inflammation such as swelling or redness to injured areas
Normal cortisol release has a dynamic affect on daily activity. A higher than normal release is beneficial for short term stressful situations, but when this becomes persistent as with long term stress, it can cause a number of negative side effects (as listed above).
Exercising causes mild stress to the body and therefore higher than normal levels of cortisol are released. Though this increased release may seem negative, doing so through exercise is actually beneficial due to the body learning how to better regulate the release. Better regulation of cortisol increases a person’s overall threshold to stress, including stress caused by mental conditions.
As related to sleep, when cortisol regulation is out of balance, usually due to stress, it interferes with healthy sleeping patterns. Exercising improves its regulation and therefore aids in the sleeping process. As with most of the above topics, cortisol should be lowered before sleeping and therefore points to finishing exercising at least 3 hours before going to sleep.