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The Relationship between Sleep and Fitness – 7 Tips to Help You Sleep Better

Sleep and physical activity have a reciprocal relationship. There are ways you can capitalize on this relationship to improve your physical fitness, get a more restful sleep, and live healthier.

What is sleep and why is it important?

There are two types of sleep, non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). NREM sleep is divided into four stages, representing relative depth of sleep. NREM and REM alternate through a cycle during periods of sleep. Sleep disorders are characterized by an absence of a stage or irregularity of the sleep cycle. What’s supposed to occur is a progression through NREM sleep stages one through four, followed by REM sleep, and back into NREM sleep as the cycle continues. 75-80% of sleep is NREM and the other 20-25% is REM. Although REM sleep gets the most attention, it’s actually stages 3 and 4, NREM sleep, the deepest sleep, that has the most restorative benefits.

Scientists haven’t uncovered the evolutionary reason for why we need sleep. There are a few theories:

  1. Inactivity Theory – We stay inactive during our most vulnerable hours to keep us safe from predators and the inability to see in the dark. 
  2. Energy Conservation Theory – We conserve energy when it’s least efficient to seek out food.
  3. Brain Plasticity Theory – Sleep plays a critical role in brain development.
  4. Restorative Theory – Sleep allows the body to repair and restore itself, both physically and cognitively.

Restore and repair

Based on the restorative theory, the body needs sleep to rejuvenate and repair itself. There is data to confirm this theory. Some major restorative functions occur mostly during sleep, and others occur only during sleep. These include muscle growth, tissue repair, protein synthesis, and growth hormone release. This is why sleep is particularly important during injury recovery, because those tissues are also repaired during sleep. A better repaired and restored body is better prepared for both mental and physical exertion.

Exercise increases deep sleep

Studies have shown that exercise promotes a decrease in NREM stage 1, the lightest sleep stage, while increasing slow wave sleep (SWS), which is the deepest sleep occurring in stages 3 and 4. One particular study suggested that aerobic exercise earlier in the day corresponds to improved sleep quality because exercise stimulates the sympathetic nervous system. The sympathetic nervous system – the same system responsible for your fight or flight response – needs time to relax before sleep.

This bidirectional relationship is evident when it comes to energy. Slow wave sleep or deep sleep is also the stage with the highest energy production. Therefore, the better our sleep quality, the more energy we have to exercise, which further helps to boost deep sleep. A lack of deep sleep can be detrimental to our recovery and energy stores. In general, exercising earlier in the day has the best sleep benefits, while evening exercise has no sleep benefits.

Resistance training, interestingly, is not as time sensitive as aerobic activity, meaning there’s more flexibility when you can perform that style of workout in a day to see improvements in the quality of your sleep. However, you should also take into account the type of resistance training performed. Best sleep hygiene practice is to avoid moderate to high intensity exercise of any kind 2 hours before bedtime to ensure your body can wind down

Lack of sleep has health consequences

While the reason for sleep is not entirely clear, we do know that we need it. So, what happens when you don’t get enough?

When we lack sleep, our cognitive functions, blood sugar regulation, and cardiovascular systems can suffer, which affects our ability to perform. Your energy levels decrease when it comes to exercise and fitness training, and the sleep-exercise cycle can negatively reinforce itself. With chronic poor sleep, you will feel exponentially more tired when you are active and exercising.

Other consequences include:

  • Cognitive effects from sleep deprivation include reduced working memory, attention, long term memory, and decision making.
  • Sleep deprivation increases your risk of developing type II diabetes. Studies have shown that lack of sleep promotes glucose intolerance and insulin sensitivity. Sleep irregularity and excessive sleep are also contributing factors, making consistent sleep habits optimal for long term health.
  • Irregularity in sleep leads to a greater risk of cardiovascular disease. Like type II diabetes, the risk is not only related to sleep deprivation, but variations in sleep duration from day to day.

Poor sleep comes from lack of sleep and changes in sleep patterns. The best way to optimize sleep for your health is to maintain consistent sleep and awake times, even on weekends.

7 ways to optimize the positive cycle between sleep and exercise

There are a few things we can do to optimize both our sleep and our physical fitness due to their bidirectional relationship.

  1. Get enough sleep. The ideal sleep range for adults is 7 to 9 hours.
  2. Maintain a consistent sleep schedule by going to sleep and waking at the same time every day.
  3. Exercise no later than 2 hours before going to bed. Earlier in the day is best to allow time for the body to relax and prepare for sleep.
  4. Resistance training can be done at any time and will also help with sleep.
  5. Exercise outdoors to expose yourself to more natural light. This will help regulate your circadian rhythm. Sun exposure in the morning is most beneficial.
  6. Prioritize restorative sleep which will allow for greater muscle growth and strength (versus poor sleep which can lead to decreased muscle strength).
  7. Perform moderate aerobic exercise for at least 30 minutes per day to start seeing sleep benefits.

Making lifestyle changes isn’t easy. Finding the energy to exercise and the time to adjust your sleep schedule is a challenge for most people. We’re here to understand your lifestyle, preferences, and impediments to change – and help you add more movement to your daily life. Please engage with your Harrison Healthcare Exercise Physiologist to get started towards better sleep, more energy, and improved fitness.


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