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Sleep is a significant contributor to our health, wellbeing, and sustainable high performance. It is important that we consider sleep within the mind-based and body-based skills and strategies.
Recovery is an essential component within The Practices of the Healthcare Athlete. It is crucial for the promotion of health, wellbeing, and sustainable high performance. Sleep is a significant element of a comprehensive recovery routine. In addition to its substantial contributions to recovery, sleep is also critical for our physical, mental, and emotional health. There are numerous benefits that sleep provides to each of these aspects of our health which have been described in further detail in past articles. In addition, the lack of sufficient sleep duration and quality has been associated with numerous physical, emotional, and mental ailments and diseases. For all of these reasons, sleep is an essential element of a healthy lifestyle. It should be emphasized that, although sleep is mentioned as single entity, it consists of several components. These include the duration of time we spend asleep and the quality of the sleep, including time spent in different stages of sleep, restfulness, and frequency of awakenings.
In addition to the clear benefits sleep provides to our health and wellbeing, it is an essential component in the pursuit of sustainable high performance. This is due to its impact on health as well as recovery. Without sufficient recovery between high demand tasks, events, and situations, it is not possible to pursue high performance in a sustainable fashion. The resources expended during such activities must be restored in order to be adequately prepared for future events. Just as there is no potential for sustainable high performance in the absence of health and wellbeing, so too there is limited potential to consistently be at our best over a prolonged duration of time without adequate, if not optimal, recovery.
There are several metrics which can be utilized to measure and provide feedback regarding the extent of our recovery. Wearable technologic devices on the market typically provide a score that indicates the extent of recovery. Different algorithms may include and weigh factors in different ways, however common considerations within the recovery score include sleep quality and duration and measurement of heart rate variability (HRV), typically as an average while asleep. An additional device provides a measure of stress resiliency in part on the basis of real-time measurement of HRV, rather than an average measure during sleep. The determination of HRV is a significant indicator of the extent of recovery of the autonomic nervous system, the ultimate determinant of the degree of variation between heart beats. While a measure of average HRV during sleep provides useful information regarding the extent of recovery, the real time assessment of HRV is a more dynamic indicator of autonomic nervous system function.
Chalmers et al (2022) investigated the association between sleep quality and duration on HRV. Their study consisted of a cross-sectional analysis of 60 healthy participants between 18 and 45 years of age. Outcome measures consisted of a measure of sleep quality (the Pittsburgh Quality of Sleep Index), a general health questionnaire, and ECG data which was used to measure heart rate and determine mean HRV. They subsequently stratified the average HRV on the basis of high and low frequency. A social stress test was employed to evoke a stress response amongst study participants and the authors then determined the correlation between HRV at rest, HRV during the stress test, and sleep quality. They reported an association between daytime function, self-reported sleep quality, sleep score, and HRV during the stress test. A predominant sympathetic state was noted amongst those with poor sleep quality. On the basis of the study results, the authors inferred that poor sleep resulted in negative impact on daytime function and lower HRV during the stress test. Limitations of the study included the cross-sectional nature of the study, averaging of ECG data which was used to determine HRV, and the lack of objective metrics to quantify sleep duration and quality.
The results of the study demonstrate the significant impact of sleep on recovery, as measured through HRV. The impact on daytime function reported in the study also provides evidence regarding the resulting deleterious effect on our ability to perform at our best following poor quality sleep. These findings are supported by the decreased HRV during the stress test following poor quality sleep. This association indicates that sleep, both with regards to duration and quality, should be strongly considered within the mind-based and body-based skills and strategies commonly included in the promotion of health, wellbeing, and sustainable high performance. In addition, from a polyvagal informed perspective, it becomes worth considering that sleep should be acknowledged when identifying our biological state, particularly given the study finding of an association between sympathetic state predominance following poor quality sleep.
Another important consideration with respect to sleep is the impact on performance. This study provided evidence of an association between poor sleep quality and daytime dysfunction. It would then be expected that performance of tasks would likely be reduced on account of poor sleep quality. When our skill and/or task execution is not aligned with the expectation or anticipation of our ability to perform these tasks, we frequently neurocept this discordance as a cue of threat or risk. This principle has been termed a violation of expectancy by Michael Allison (a more detailed discussion of this concept will be the focus of an upcoming article). In order to avoid such a situation and, effectively, exposing ourselves to cues of threat and risk and the associated sympathetic, or possibly dorsal vagal, states that ensue, it becomes prudent to consider either adjusting our tasks or our expectations on the basis of our sleep quality. In order to make adjustments either to daily tasks or to our expectations of our ability to perform these tasks, incorporation of metrics, such as sleep quality, HRV, and recovery scores can be beneficial.
Another important consideration emerging from the findings of the study relates to the impact of sleep on our autonomic nervous system as well as the potential for our biological states to impact our sleep. It has been well described that sleep quality affects numerous biological processes and systems, including our autonomic nervous system. However, what is worth considering, and is less often discussed, is the extent to which our biological states may impact our sleep quality with consequences then feeding back on our subsequent biological states. For instance, many, if not most of us, have had the experience of poor quality sleep when we are in a sympathetic, anxious state at the time of trying to fall asleep. Poor quality sleep can then lead to sympathetic predominant states, as described in the study. Emerging from the concept of the biological state as an intervening variable (described in past articles), this then increases the likelihood of our neuroception being biased towards cues of threat, risk, or uncertainty, thereby further increasing the sympathetic predominant state. Future research regarding the impact of sympathetic and dorsal vagal states, in comparison to ventral vagal states, on sleep duration and quality would be highly informative in this regard.
Sleep is a crucial element to include within the skills and strategies of The Practices of the Healthcare Athlete. It is a critical element in the promotion of our health, wellbeing, and sustainable high performance. It is important to recognize both sleep duration and quality when considering the impact of our sleep on our daytime function and longer term goals of being at our best on a consistent basis over a prolonged duration of time. Incorporation of technologic devices can be very beneficial in this respect.
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REFERENCES
Allison, M. The Play Zone: A Neurophysiological Approach to our Highest Performance. https://theplayzone.com.
Chalmers T, Hickey BA, Newton P, Lin C-T, Sibbritt D, McLachlan CS, Clifton-Bligh R, Morley JW, Lal S. Associations Between Sleep Quality and Heart Rate Variability; Implications For a Biological Model of Stress Detection Using Wearable Technology. Int J Env Res Public Health; 2022: 19: 5770.
