We know sleep is imperative to health. But people seldom realize the extent it affects our recovery and susceptibility to injury. As a physical therapist, I have a special interest in how sleep affects both the risk of becoming injured and recovery from existing injury. So this article is going to be all about sleep – both in general and as it specifically relates to injuries.
 
In an effort to improve the quality of my own sleep, I have done a lot of research on the subject and have even tried out a number of sleep apps. Though my app would tell me the percent of deep, REM, and light sleep I got each night, I still had some questions. I've uncovered the answers, and will be sharing them with you today.
 
  • What percentage of each type of sleep should I be aiming to obtain? 
  • How does sleep specifically influence recovery? 
  • How can I improve my sleep cycle, not simply the quantity of sleep I’m getting? 
 

The Benefits of Sleep

Precision Nutrition has a fantastic article all about sleep, and I highly recommend checking it out. Here's a quick synopsis of the important points:
 
  • Effects on Weight Management: The average adult gets around seven hours of sleep each night. Studies have suggested that less than six hours, or more than nine hours a night, leads to weight gain compared to those who sleep 7-8 hours a night. People who sleep less than six hours a night are significantly more likely to be overweight or obese.1,2 It’s not clear why people who sleep more than nine hours a night have similar weight concerns. 
  • Effects on Skill: During sleep, the body repairs damaged tissues, produces crucial hormones, and strengthens memories. This strengthening of memories helps you perform skills better after sleeping than if you had spent that time instead just practicing while awake.
  • Effects on Immunity: Have you ever noticed you tend to get more colds when you are run down? That's because sleep also aids in immune response, allowing your body to create more white blood cells to fight harmful viruses and bacteria. 

 

quality sleep

See her? She's getting slimmer, stronger, and healthier. Are you giving yourself the time to do the same?

 

The Five Stages of Sleep

  • Stages one and two are both stages of light sleep. Stage one should account for approximately 4% of your entire cycle and stage two 45-55%. During these two stages, muscle activity slows, as well as your breathing and heart rate. Your body temperature also decreases.
  • Stages three and four are stages of deep sleep. Stage three should account for 4-6% of your sleep cycle, and stage four, 12-15%. During these stages your brain begins to generate delta waves (the slowest brain waves and the point when our brain waves are least like waking), your breathing becomes rhythmic, and your muscle activity is limited. This is also the stage where growth hormone secretion occurs.
  • Stage five is REM (Rapid eye movement) sleep. It should account for 20-25% of your sleep cycle, and during this stage your brainwaves speed up and dreaming occurs. Muscles relax (extremities are usually paralyzed) and your heart rate increases. Your breathing is rapid and shallow. 
 
A full cycle of these five stages typically takes about ninety minutes.1 Now that you know what ratios are ideal, you can work to improve the quality of sleep you get. This will ensure you cycle through these stages without interruption. Keep reading for some tips on how to improve the quality of your sleep. But first, a bit about the relationship between sleep and injury.
 

Sleep and Injury

There isn’t a ton of specific research on sleep and injury, but the relation between the two is starting to come to light. Most notable are a couple of studies conducted with youth athletes. One concluded that injury rates increased during games following a night of sleeping less than six hours.3 The other found that sleep was the strongest predictor of injuries, even more than hours of practice4 (read this piece for a full breakdown). Inadequate sleep was correlated to decreased reaction time under fatigue, as well as a diminished immune system, as discussed above. Decreased sleep also doesn’t give the body the time it needs to repair tissues. Over time this damage can lead to injury.
 
British researchers have been looking into the relationship between sleep and arthritis.5 In Britain, it was estimated that nearly two in three people with pain secondary to arthritis experience trouble sleeping. Researchers was always thought these sleep problems were caused by the pain, but recently they have discovered that it’s actually a two-way street. Sure, joint pain causes sleep disturbances, but sleep disturbances will actually make joint pain worse and accelerate joint damage. According to medical director of Arthritis Research UK, Alan Silman, “Pain induces lack of sleep and lack of sleep induces pain.”5
 
This could also involve the disruption of the immune system. When you are overtired, the immune system is saturated by the distress the body is experiencing. This is why it’s so much easier to get sick while sleep deprived, and also why it's hard to recover from injuries without adequate sleep.
 

4 Simple Ways to Improve Sleep Quality and Quantity

There are a number of different ways to improve your sleep quality, feel more rested, and be less prone to injury. Here are some of the most agreed-upon techniques, as well as strategies I have personally implemented that have made a huge difference.
 

1. Make a Bedtime and Wakeup Routine

This one is simple. Creating a routine around sleep is so effective because it prepares you mentally and physically. Try to go to bed and wake up at the same time every day. Your brain and body develop a natural circadian rhythm, and learn that sleep is the next thing that needs to happen.
 
My routine includes having a small snack about an hour before bed (usually celery and almond butter), followed by reading a fiction book (I get too involved in planning if I read a business or non-fiction book) for 30-60 minutes. When I wake up, I drink a full glass of water before getting in the shower, followed by breakfast at the dining room table to sit and relax before heading to work. This is what works for me, but you need to find what works for you. I know some people who swear by taking a hot shower before bed, and others who love to color. Try a few things out and see what works best for you.
 

2. Turn Off Electronic Devices One Hour Before Bedtime

The light emitted from our devices - computers, iPads, smartphones - messes with our natural circadian rhythm. Our bodies use light as a cue to know when we should be awake and when we should be asleep, and the light from these devices hinders our ability to produce important hormones that facilitate sleep.
 
For those of you who might not be able to do this, I have heard fantastic things about an app called F.Lux. It will change the light emitted from the device gradually to help prepare you better for sleep.
 
cell phone in bed
The light from electronic devices tells your body that it's time to be awake. Not ideal when you're about to try and sleep.
 

3. Avoid Excessive Caffeine – Even in the Afternoon

The stimulant effects of caffeine last much longer than you might think. I recently started using a new app that tracks your caffeine intake and shows when you will be ready for sleep. The most interesting thing wasn’t when I was considered “ready” for sleep, but that I still had some caffeine in my system from the day before when I woke up in the morning. Consider this when you reach for your afternoon or evening coffee. Some research suggests that you should never drink caffeine past 2pm, but I opt for nothing after noon.2
 

4. Try a Sleep App

Sleep apps increase awareness of your quantity and quality of sleep. They provide a visual log of how long you’ve slept, and the ratio of each stage of sleep. By comparing these logs as you adjust things in your day, you can become more aware of the factors affecting the quality of your sleep. Tracking sleep quality made me realize that for me, cutting electronics an hour before bed made the biggest difference.  
 

Prioritize Quality Sleep

I wanted to bring all of this information in one place so you can realize how important sleep is for everything, including injury prevention and recovery. Getting adequate sleep could even aid in pain management. Remember there are different stages of sleep, and aim to hit the right ratios for each:
 
  • Stage One: 4%
  • Stage Two: 44-55%
  • Stage Three: 4-6%
  • Stage Four: 12-15%
  • Stage Five: 20-25%
 
I hope you have learned a few strategies to help improve your own sleep. Take a few minutes and think about how you could improve your sleep habits. Ask yourself these questions: 
 
  • Do I have a regular routine for bedtime and waking up in the morning?
  • Do I turn off my electronic devices at least an hour before bedtime?
  • Do I avoid caffeine after 2pm in the afternoon?
  • Do I use any sleep apps to increase awareness of my sleep quality and quantity?
 
If you answered “No” to any or all of these questions, you’re missing out on better sleep. Take a step today to improve. Your body and your mind will thank you.
 
More on the Power of Sleep
 
References
1. Andrews, R. "All About Sleep." Precision Nutrition, Accessed February 27, 2016. 
2. St. Pierre, Brian. "Hacking sleep: Engineering a high quality, restful night." Precision Nutrition, Accessed February 27, 2016.
3. Luke et al. "Sports-related injuries in youth athletes: is overscheduling a risk factor?" Clinical Journal of Sport Medicine 21 no. 4 (2011): 307-14.
4. Milewski et al. "Chronic lack of sleep is associated with increased sports injuries in adolescent athletes." Journal of Pediatric Orthopaedics 34, no 2 (2014):129-33.
5. Yapp, R. "Why lack of sleep may trigger arthritis—but treating insomnia may improve the condition." Mail Online. 2012. Accessed February 25, 2016. 
 
Photos courtesy of Shutterstock.
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