Sleep is essential to sustaining life. Yet the majority of us are casually dismissive when it comes to sleep. We routinely deny ourselves this most critical sustenance of our own volition. The attitudes towards sleep among high performing individuals in different realms and society in general are quite baffling. We also largely fail to make the connection between the reckless lack of care and attention we give to our sleep and the dizzying array of consequences that inevitably follow. Objectively this behaviour is bizarre, and our failure to prioritise sleep defies logic. With this latest Informed Blog we explore the myriad ways you lose when you don’t snooze sufficiently.
Like other animals humans have a biological drive to sleep. Yet unlike other animals we are increasingly choosing not to heed the call. Among high powered types it has been a badge of honour to work long hours and sleep sparingly. Cool kids stay up late, just as rock and roll types rejoice that they will sleep when they’re dead. Such attitudes have influenced societal norms when it comes to sleep habits. Those of us who operate in the realm of sport are far from immune from this lemming-like behaviour.
Perhaps due to our sleep-deprived state, we have been slow to connect these trends with the burgeoning public health issues that have coincided. This chronic sleep shortage is a problem of our own making, and over recent decades with modern lifestyles and the ubiquitous presence of technology the signs are that declining sleep is epidemic in countries like the United States, and may become a pandemic.
A DAWNING REALISATION…
For athletes, coaches, and professionals across disciplines sleep is not only critical to success in the sporting realm, but is also essential to our health (and of course those two things are inextricably linked). The recent period has seen a growing level of recognition and a number of publications in the sports science and medicine literature on the topic of sleep. It is increasingly widely acknowledged that sleep is crucial for athletic performance, particularly in sports with an element of perception, cognition, and decision making. The consequences of failing to pay attention to sleep goes beyond inhibiting performance. Dramatically increased injury and illness is another price that we can expect to pay for chronic lack of sleep.
Yet amidst this greater recognition of the importance of sleep for athlete health and performance in the literature, sleep remains widely neglected among athletes. Moreover, coaches and practitioners themselves seemingly fail to realise that they are not exempt. Turns out we are all human, so can expect to suffer the consequences of failing to prioritise sleep from professional, relationship, and health perspectives.
I consider myself quite ‘woke’ when it comes to the critical importance of sleep. I had the realisation early in my undergraduate studies that if I wanted to avoid succumbing to whatever cold or flu virus was circulating the student body I needed to double down on my sleep. At the time the notion that sleep could have such a profound impact on my health and immune function was something of a life-changing revelation, and the lesson has stayed with me. Like many others I have also suffered from insomnia at various times in my adult life, which very much teaches you to appreciate sleep and the impact that a lack of sleep can have.
Yet until I recently read the excellent book ‘Why We Sleep’ by Professor Matthew Walker I did not fully appreciate the extent to which sleep is essential to every part of how we function.
STAYING IN THE GAME..
Prospective studies have established that a major determinant of success in achieving athletic goals is the extent to which athletes manage to avoid enforced absences from practice and competition due to illness or injury. The links between insufficient sleep and the incidence of accidents and injuries are well established. For instance, a notable finding for youth athletes from the investigation by Milewski and colleagues was that the adolescent athletes studied who averaged less than 8 hours’ sleep reported exponentially higher incidence of injury.
As I can personally attest to, sleep is also central to immune function. The immune response is dampened by acute sleep loss to the extent that getting a flu shot when short on sleep has considerably less of a protective effect as a result. Just as with injury, habitual sleep patterns are directly implicated in the incidence (how many times you get sick) and severity of illness (i.e. how long you’re out of action) among athletes. Investigations that expose participants to an active cold virus demonstrate that participants who slept less report significantly higher rates of succumbing to the cold virus during the follow up period, compared to those who slept for more than 7 hours.
In other words, if success in sport is directly linked to avoiding enforced absences due to illness and injury, and incidence of illness and injury are in turn directly linked to how much sleep athletes report, then sleep represents a major factor in determining athletes’ ability to be successful in their sport.
SLEEP AND PERFORMANCE…
Athletes’ physiological capacities are acutely impaired by lack of sleep. Endurance performance is especially susceptible to these deleterious effects. The acute physiological response to exercise is altered when in a sleep deprived state, with changes in both metabolic function and also the autonomic nervous system responses that occur both during and following the training or competition bout. Perceived exertion also tends to increase, so that the same relative intensity feels harder.
Performance capabilities over time are also hampered with chronic sleep shortage. As athletes experience less of the restorative effects of sleep, including repair of tissues, the regeneration between practices and competitions is impeded. The adaptive response to training is also severely impacted, negating much of the benefit that would otherwise be derived.
Another way to illustrate the adverse effects of lack of sleep on performance is the significantly improved performance observed following interventions that redress the sleep debt. Implementing extended sleep over a period of days can significantly improve physical and skill performance metrics following the intervention. For instance, significant improvements in field goal and free throw shooting percentages in college basketball players and serving accuracy in tennis players have been reported following sleep extension interventions. Even an acute intervention on the day - i.e. simply having a nap, can confer significant short term performance benefits.
Neurocognitive function is also significantly impacted by lack of sleep. The degree of impairment is akin to being legally drunk. Reaction times become sluggish, and the coupling between stimulus and response goes awry. As a result accuracy is impaired, both in terms of response selected and execution of the chosen action.
Higher cognitive functions are particularly prone to the effects of sleep deprivation. Cognitive tasks that require more conscious attention and directed mental effort are particularly affected. With acute or chronic sleep shortage we tend to revert to autopilot, becoming less vigilant and more prone to lapses in attention. Executive function is compromised, so that attentional resources are reduced and the ability to manage, direct, and switch attention is also impaired. Decision making likewise suffers as we are not only less able to attend to and process relevant information, but also less capable of strategic thinking. Our capacity for rational thinking is also impaired in this state.
Each of these factors individually and collectively harms performance. Case studies suggest this is likely to be reflected in selection and the minutes that players get on field or on the court. Late night tweeting is associated with impaired performance based on game metrics on the following day in professional basketball players. Such findings also demonstrate the role of smart devices and social media in driving sleep restriction.
Whilst negative physiological and performance effects of acute sleep restriction are evident from such studies, the more consistent findings of negative effects are reported with measures of chronic sleep shortage accrued over time, such as average nightly sleep duration.
DEVELOPMENT IN CHILDREN AND TEENS…
Sleep plays a fundamental role in our development during the early years and throughout the pivotal periods of childhood and adolescence. Sleep remains integral to neuroplasticity throughout life, but the function of sleep is especially crucial to brain development during infancy, childhood, and adolescence.
There are three main discrete categories of sleep: light NREM, deep NREM, and REM. One of the defining characteristics of REM sleep is rapid eye movement, hence this quality has been used to separate the three types, but there are other characteristics that differentiate them, particularly the nature of the brain waves observed. We cycle through these respective stages but the relative proportion of deep NREM sleep is greater early in the night’s sleep, whereas REM sleep and light NREM sleep predominates later in the sleep bout.
Young infants have a higher proportion of REM sleep than at any other time in life. During this time the ratio between NREM and REM sleep is 50:50. The distribution between NREM and REM sleep only arrives at the 80:20 split sleep seen in adulthood once athletes reach late adolescence.
REM sleep is involved in building the architecture of neural circuits. NREM sleep serves to prune the mass of circuitry laid down and organise the neural connections made. NREM and REM sleep thereby works in combination to create, remodel, and update neural circuitry.
Deep sleep (i.e. both REM and deep NREM sleep) in particular is identified as the driver for maturation of the brain and neural circuitry underpinning cognitive and motor skills. Sleep in young infants is involved in the construction and development of the cerebral cortex. Development of the frontal lobe, which is instrumental to reasoning, rational thought, and critical thinking, is the final part of brain development that occurs during the latter stages adolescence.
For student athletes this is highly pertinent. During adolescence when frontal lobe development takes place, there is a critical need for the deep sleep and the requisite blend of sleep components to foster the neural development needed to navigate the increasing complexities of the world around them.
Both duration and quality of sleep is therefore paramount for youth athletes. Sadly practice and academic schedules imposed on high school student athletes present obstacles to getting the duration and quality of sleep required. In many cases, high school athletes are required to attend early morning practices, and practices in the evening, often leading the athlete to stay up late simply to get their homework done.
Beyond scheduling demands, for the first time our youth are growing up in the constant presence of devices specifically engineered to hijack their attention with applications that are highly addictive. Exposure to these devices and the conditioned behaviours associated with them in itself is disrupting our sleep. As a result, even when the schedule permits adequate opportunity for sleep, many athletes still fail to get the required amount on a consistent basis. Screen time, particularly later in the evening, is linked to increased sleep latency (that is, it takes longer to fall asleep) and decreased sleep quality.
Given the integral role of sleep in brain development and neurocognitive function, the consequences of chronic sleep shortages in youth athletes go beyond sport. Aside from sporting performance, sleep in children and adolescents also shows direct association with tests of IQ and scholastic performance.
The impact of sleep on the grade point average of student athletes should be a serious concern. What is deeply troubling is that sleep disturbances are further linked to the mental health issues that are becoming increasingly prevalent among student athletes.
INFORMATION PROCESSING AND MEMORY…
Information capacity is directly linked to sleep status. We have identified that sleep is integral to synapotogenesis, i.e. making new connections in the brain. Acquiring new information and task based knowledge is accordingly supported by sleep. For instance, if you take a nap after a training session or sleep between consecutive sessions the new memory is stronger and you have superior recall than if you had stayed awake in between.
Consolidating newly acquired information and explicit knowledge into memory occurs during non REM sleep. Retention and recall is therefore correlated with the relative quantity of NREM sleep the previous night.
Stage 2 light NREM sleep frees up working memory capacity for new information. This function of sleep in managing working memory capacity means that the duration and quality of your sleep the previous night has a direct bearing on your ability to take on board new information and to acquire knowledge the following day.
LEARNING AND ACQUIRING SKILLS…
Consolidation and retention of explicit knowledge or newly acquired fact-based information is predominantly the domain of NREM sleep. In keeping with its role in pruning neural circuitry, NREM sleep is also central to the process of selectively retaining pertinent information, and discarding what is less relevant from the masses of inputs and bytes of information we are exposed to each day. In the Information Age, this function of sleep has never been more crucial.
Aside from acquiring facts and new explicit knowledge, sleep has a central role in skill learning, including the implicit learning that is a major part of how we acquire language and motor skills. In particular, the consolidation and refinement motor skills acquired is supported by sleep. Participants demonstrate enhanced speed and accuracy when tested on motor skill being learned when practice bouts are separated by a night’s sleep. This effect is not observed when the same practices and assessment are undertaken without sleep between practices
We can therefore contend that rather than practice alone, it is actually practice accompanied by sleep that leads to mastery of movement skills. When we allow sufficient sleep, we are effectively able to continue to work on and refine our motor skills offline. In particular it is the stage 2 NREM sleep that occurs later in the night which is implicated with this effect. That said, REM sleep is also involved in creating associations, and divining the higher order structure that links and governs elements of complex tasks.
INSPIRATION AND CREATIVE SOLUTIONS…
It has long been known that sleeping on a problem serves us well. In the dream domain of REM sleep we are freed from conventions and constraints. The mind is given free rein to play with outlandish scenarios, and consider the task or situation in abstract ways.
Sleep brings enormous value to problem solving, not only lending novel insights and alternative perspectives on the problem, but also conjuring up less intuitive prospective solutions. This is important, as in many instances the best solution differs to what is more immediately obvious.
If sleep is integral to coming up with inspired solutions and creativity, then failing to get the required amount of sleep on a consistent basis robs us of these gifts. Sleep provides us with inspiration. It allows us the capacity for free thinking, to conjure up creative solutions, new ideas, and novel insights. Without sufficient sleep we are become automatons. This has implications for coaches, practitioners and athletes alike if we wish to be (and remain) successful.
BODY COMPOSITION AND DIETARY INTAKE…
When we are getting insufficient sleep this alters our dietary habits and over time leads to adverse changes in body composition. Ultimately, this may present a performance issue for athletes, and a health issue for coaches and practitioners.
Sleep affects both appetite and food choices. We get hungry when we are tired and sleep deprived, and so tend to eat more. However, we also crave particular types of food, so disproportionately increase intake of high energy snack items, which compounds the issue.
Finally, just as the metabolic and physiological response to exercise is altered when in a sleep-deprived state, our biochemical response to feeding is also altered. In particular, our insulin response and how we regulate blood sugar quickly becomes impaired. Following less than a week of insufficient sleep we can expect to present in a way that would be classified as pre-diabetic.
Conversely, sleep is crucial for those seeking positive changes in their body composition. This is under recognised as a key factor in how body mass changes are regulated and what compartments of the body this comes from. Most athletes are seeking to reduce fat mass and conserve or increase lean mass. With habitual sleep shortage the opposite occurs – fat mass is conserved, so the weight that is lost is at the cost of lean mass.
MOOD AND EMOTION REGULATION…
Lack of sleep affects our mood. The likelihood of negative affect (self-reported negative emotions such as anxiety, fear, and anger) is increased, whereas positive affect (positive emotional states) is reduced when in a sleep-deprived state.
Aside from mood state, our ability to control our emotional equilibrium and regulate our emotional response to external events is also impacted by sleep. We experience an increase in what is termed ‘emotional reactivity’ when we have not had sufficient sleep. For instance, we are quicker to anger, and other negative emotions are also triggered more easily.
Aside from not being much fun to be around when we are irritable, the effects of lack of sleep are also likely to impact how we conduct ourselves and how effective we are able to be. We are also likely to become frustrated more easily, which is not conducive in either a practice or competition environment. The effect of sleep on emotional state adds to non-training stress, and makes us less able to handle the challenging situations that are ubiquitous in performance sport.
Once again, when extended sleep opportunity is permitted (or imposed) for a week, mood scores quickly rebound and show a significant increase, as has been demonstrated by an investigation of female college track athletes. This illustrates that our mood is dragged down under the weight of insufficient sleep, but this can be lifted when we make the decision to prioritise our sleep and make the necessary changes to our schedule and behaviour.
SOCIAL AND EMOTIONAL INTELLIGENCE…
The ability for us to demonstrate and develop social and emotional intelligence are highly impacted by sleep. Lack of sleep affects how we perceive the world and those around us. Sleep status affects our acuity in detecting non-verbal cues, such as body language and facial expression. We are considerably less accurate in how we interpret and differentiate between different expressions and gestures when short on sleep. We are not only more likely to misinterpret these social cues, but also more likely to perceive them as hostile.
The importance of sleep in supporting social and emotional intelligence becomes increasingly evident as we enter adolescence. Along with the aforementioned sleep-dependent development of the frontal lobe, sleep is also critical to being able to successfully conduct day to day interactions, cultivate relationships, and navigate increasingly complex social structures.
Whether we are an athlete, a coach, or a practitioner, the impact of sleep on these capabilities has a host of implications. Successful athletes know it takes a village, so even in individual sports the ability of an athlete to foster and maintain good relationships with those who support them on the journey is paramount. Clearly in a team sports context the social dynamics between the players and with the respective members of the coaching and support staff are absolutely critical to team success. The status of the personal relationships beyond the practice and competition environment also have a major bearing on the global stress and wellbeing of the athlete, which ultimately impacts performance.
MENTAL HEALTH AND WELLBEING…
There is a bi-directional relationship between stress and sleep: stress can affect sleep, but lack of sleep also affects our stress levels. The duration of the prior night’s sleep is demonstrated to affect stress levels reported the next day.
As we spoke about in relation to mood, sleep status also affects our general sense of wellbeing. Chronic sleep shortage tends to instill a general sense of malaise.
In addition to being a source of stress, lack of sleep further impacts our coping resources to deal with that stress. Shorter habitual sleep durations are negatively related to measures of ‘resilient coping’.
Both sleep duration and quality are crucial for emotional resiliency and our faculties for coping. Sleep (and REM sleep in particular) is integral to how we cope with traumatic events. Dealing with events in the dream domain helps take the emotional sting out of what has happened and how it has impacted us.
REM sleep is crucial for our sanity. Impaired duration and sleep quality impacts emotional instability. In severe cases chronic sleep disturbance leads to psychosis. Whilst this might seem extreme, we need to recognise the impact that sleep can have on our emotional wellbeing and how this can influence our behaviours. A nationwide study identified that self-reported insomnia was a consistent predictor of suicide ideation. Similar findings were recently reported in student athletes (and non-athletes); both insufficient sleep duration and symptoms of insomnia were found to be independent predictors of reported suicide ideation in the college students studied.
HEALTH AND LONGEVITY…
Sleep is essential to sustaining life. Habitual sleep behaviours are directly linked to all-cause mortality. In other words, depriving ourselves of sufficient sleep will shorten our life expectancy and negatively impact the quality of life you do have. Total lack of sleep for a sustained and prolonged period will in fact kill you as a surely as a lack of food (and in about the same amount of time).
Sleep is also a major lifestyle risk factor for a host of chronic diseases, including heart disease and diabetes. Sleep is further implicated in cancer risk and survival rates. Finally, sleep is identified as a mediating factor for the onset and progression of neurodegenerative conditions, such as Alzheimer’s.
Sleep is essential for all humans, but particularly those who seek to push the boundaries of human endeavour. As we have explored, failing to prioritise this most vital source of sustenance for our mind and bodies impacts every part of our day to day life as athletes, coaches, and practitioners. Hopefully this information helps to provide the wake up call that is needed to take the next steps to change our behaviours. Please share this with your athletes and colleagues (and I heartily recommend the book ‘Why We Sleep’ as bedtime reading).
If you found this a valuable read, see the Books section for more on a variety of topics relating to athletic preparation, sports injury, and coaching athletes.