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7/1/2023 Newsletter

This newsletter will be a little different from previous newsletters. Instead of breaking down individual studies I am going to write about general themes from 4 studies about sleep, how it impacts our health, and how it impacts performance/gains.


We all know fairly well that sleep is important for our health and fitness. Adults are recommended to get between 7-9 hours of sleep per night. Most Americans struggle to reach that and on average are deprived of sleep by 1.5 hours a night. 40-65% of adults self report getting less than 7 hours of sleep per night. It has been observed that over the last 100 years the average length of sleep has reduced from 9 hours in 1910’s, to 7.5 hour at around 1975, and under 7 hours per night now. A good nights sleep includes several factors not just duration. This would include it taking less than 15 minutes to fall asleep, one or no times awake in the night, reduced time awake from when your “bed time” was, and when you plan to be awake, and sleep efficiency (the time asleep vs time in bed) of 85% or higher. Poor sleep is when it takes 60 or more minutes to fall asleep, you wake 4 or more times per night, wake up after being asleep already for 51 or more minutes, and 64% or lower sleep efficiency.


It has even been seen due to demands of sports, school and other activities that children now are even averaging as little as 5-6 hours of sleep per night. There is also correlation between lack of sleep and obesity but is likely a complex relationship that relates to priority towards health promoting habits, and or lack of control over those behaviors due to a number of social, environmental, and economic factors.


To start off lets discuss how sleep impacts things like hunger and feelings of being full. Looking at several studies there is a relationship between lack of sleep and issues with feelings of being full and our drive to eat. Lack of sleep is highly associated with feelings of subjective hunger. Restricted sleep results in around 250-350 increase in calories consumed per day and an increase in weight in those who have restricted sleeping patterns. It is also thought that this results in a worse response to insulin. Insulin is a hormone that works to take glucose from the blood and shuttle it towards tissues for energy. Being less sensitive to insulin means it takes a larger dose to have the same effect and has negative health effects beyond the scope of this article. It has also been observed that there is altered brain activity when it comes to food when we are restricted in sleep, where the areas responsible for reward and pleasure are more stimulated by food, which often results in overeating and eating for reward/pleasure versus for maintaining energy levels and our bodies. This is important because with food it is often observed that extremely palatable foods (good tasting, with pleasant textures, high in salt, fat and sugar) can result in an override towards normal feelings of fullness and hunger. Think of it this way if you have a meal and feel full and someone walks out with your favorite food and asks if you wanted some how likely are you to eat it? Some of these examples dont fit in, while in prep, or if we are strict at tracking macros/calories but I think we can relate to the topic.


We also see under sleep restriction we have less cognitive control to turn down foods, this also impacts concentration, learning, memory, ability to recall information, and mental health issues. For example, in those who work night shifts there seems to be a link to sleep dysregulation, cardiac and metabolic dysregulation, particularly if someone goes between nights and days. Issues with sleep duration in most people have been linked to increases in snacking, choosing more calorie dense foods, and lower intakes of fruits and vegetables.


Even when trying to lose weight studies have shown that even with calorie restriction lack of sleep directly affects the amount of weight someone loses. In studies looking at 2 week calorie restriction with normal sleep or sleep restriction, groups with sleep restriction lose less weight. And better sleep quality and longer sleep durations are more associated with successful weight loss. In those who are lacking adequate amounts of sleep just adding in more time spent sleeping results in on average 270 calories less consumed per day. This relationship also seems to go both ways, as those who often achieve 5% weight loss report improved sleep and have less pain and issues with high blood pressure. These changes might be related to the “fight or flight” system (in simple terms). And this does not just impact our behaviors associated with food and weight loss, but this also impacts injury risk and recovery.


It has been suggested that sleeping under 7 hours per night has almost a 2 fold increase in risk of musculoskeletal (MSK) injury, particularly if that is sustained for 14 or more days. Further, loss of sleep and pain have a relationship, as it can be observed that loss of sleep often leads to more next day pain, while pain doesn't necessarily as strongly predict loss of sleep (at least in athletes). Also it is suggested that those who get >8 hours of sleep had a 61% reduction in injuries compared to those who slept less than 8 hours. This effect again might not be significant until it becomes a loss of sleep over several days. This is further seen in Military populations where those who got under 4 hours of sleep were over 2x more likely to have an MSK injury. This is also seen in overtraining studies, where there is so much training occuring it impairs sleep and sleep quality, and many authors suggest that its not just due to the training load. But a lot of this needs to be taken with a grain of salt due to use of self report measures.


Self-report measures can be an issue because of our ability to recall information, this is bias due to our memory sometimes not always being accurate or reliable to what actually happened. Also some statistics mentioned before can be flawed, as without looking at original data it can be misleading. For example, if you had a sample of 100 people and 4 got injured who slept under 8 hours a night and only 2 got injured that slept more than 8 hours a night you could say there was a 50% reduction in injury.


To date there are no studies tracking people during a sports season or as time goes on to see in the moment how sleep impacts injury rates, or injury recovery. It is currently not known if loss of sleep is more associated with certain types of injuries as well, outside of concussions. Poor sleep is likely indicators of broader issues that likely need to be addressed as well. Its also not clear if specific sleep disorders are more associated with specific types of injuries, and some populations are more at risk for development of sleep apnea. For example, those with larger body mass, neck size etc seen in sports requiring those things, and or more muscle mass have more correlation with sleep apnea ( I recommend Barbell Medicines Sleep Apnea article to learn more). There is based on self report measures a 2-3x increase in pain with declines in sleep quality, and sleep deprivation reduces the body's analgesic capacity. It also appears that reduced sleep can have substantial effects on physical performance for a number of reasons. The simplest reduced explanation would be that it makes our bodies have difficulties with adapting to previous demands as well as requiring more effort to deal with future stressors/demands


It seems lack of sleep is related to increase in heart rate during activity, worse ventilation and respiratory frequency, and lactate accumulation. So this results in worse cardiovascular performance during exercise. In particular if the exercises include more psychological demands this seems to result in faster exhaustion. In particular with aerobic based exercises this is concerning as central fatigue seems to play a key role in performance. Even in weight lifting it can be seen that peak power is usually impaired as well as RPE will be higher in individuals who are sleep deprived. Lack of sleep is also associated with worsening reaction time, which can be reduced just by one night of decreased sleep. (think of daylights saving time spring forward). There also seems to be issues with inhibitory control when we lack sleep. Think about your ability to concentrate, tune out external distraction or even internal distractions from your own thoughts. Also lack of sleep impairs memory and is associated with worse academic and job performance.


Poor sleep can also exacerbate anxiety and depression as mentioned previously. These issues also have impact on sleep and sleep quality so they have a cyclical relationship. Anxiety and depression themselves are also more highly associated with things like neck and back pain and general increased risk for injury. Many people will find that when they have poor sleep they have increased perception of stress the following day and more intrusive, unwanted off task, and ruminating thoughts (getting thoughts stuck in your head). Poor sleep can also increase pro inflammatory markers and hormones, and reduce the production of certain chemicals in the body associated with repair and recovery.


Further, it should be noted that most bodily processes occur in loops. Most people understand cortisol is a stress hormone and its not good to constantly have high cortisol levels, on the opposite end it also wouldn't be good to always have high levels of hormones associated with repair due to risk for cancers, excess bone growth, excessive scarring etc etc.


It has been noted that sleep extension interventions has a positive effect on performance as well, with improvement in reaction times, reduced daytime sleepiness and better mental health and perceptions of recovery. Caffeine, which i do not recommend as a replacement for good sleep, can counter issues with executive functioning due to lack of sleep.


Unfortunately, in some instances there is a societal attitude that lack of sleep is a badge of honor showing mental strength, rather than a bad thing that should not be glorified. So it might go a long way with changing our attitudes around sleep to elicit changes that making prioritizing sleep easier. Further, many people will use caffeine to make up for bad sleep habits which is only a temporary solution and at times exacerbates factors related to poor sleep duration and quality. So hopefully this helps you to understand why getting sufficient sleep is important and in future newsletters we can review strategies to improve sleep quality and duration.


References


Papatriantafyllou E, Efthymiou D, Zoumbaneas E, Popescu CA, Vassilopoulou E. Sleep Deprivation: Effects on Weight Loss and Weight Loss Maintenance. Nutrients. 2022 Apr 8;14(8):1549. doi: 10.3390/nu14081549. PMID: 35458110; PMCID: PMC9031614.


Zhu B, Shi C, Park CG, Zhao X, Reutrakul S. Effects of sleep restriction on metabolism-related parameters in healthy adults: A comprehensive review and meta-analysis of randomized controlled trials. Sleep Med Rev. 2019 Jun;45:18-30. doi: 10.1016/j.smrv.2019.02.002. Epub 2019 Feb 10. PMID: 30870662.


Huang K, Ihm J. Sleep and Injury Risk. Curr Sports Med Rep. 2021 Jun 1;20(6):286-290. doi: 10.1249/JSR.0000000000000849. PMID: 34099605.


Charest J, Grandner MA. Sleep and Athletic Performance: Impacts on Physical Performance, Mental Performance, Injury Risk and Recovery, and Mental Health. Sleep Med Clin. 2020 Mar;15(1):41-57. doi: 10.1016/j.jsmc.2019.11.005. PMID: 32005349; PMCID: PMC9960533.


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