Polysomnography (PSG) is considered the 'gold standard' for objectively measuring different parameters of sleep, including total sleep time, quality of sleep, and distinguishing between sleep stages. However, PSG is costly, and tends to be burdensome in terms of set-up time and invasiveness during sleep. Wearable sleep-monitoring devices could prove to be a more practical alternative to PSG.

Additionally, while EKG leads are typically what is utilized to measure heart rate (HR) and heart rate variability (HRV) throughout the night in a PSG set-up, every day-use HR monitors are also beneficial for individuals to evaluate their cardiovascular activity during different types of physical activities (including every day activities, exercise, and sleep), as well as their heart's ability to "recover" from a given activity.

The investigators propose to study the effect of the WHOOP Strap 2.0 device on sleep perception and perform a methodological study to validate the accuracy of the the WHOOP Strap 2.0 device when measuring HR accuracy and HRV accuracy, and sleep quality and quantity with respect to PSG in healthy volunteers with no self-reported sleep disorders or debilitating medical conditions.

Polysomnography (PSG) is still considered the 'gold standard' for measuring sleep parameters, such as total sleep time, sleep efficiency, and sleep stages (6). However, PSG suffers from key limiting factors for routine care applications irrespective of setting (e.g., home, acute setting, and long term setting). Some of the key limitations of PSG are the high cost, arduous application, intrusiveness to sleep, and requirement of sleep lab and dedicated infrastructure. Wearable technologies could provide a viable alternative to PSG. We are proposing to perform a methodological study aimed at validating the accuracy of WHOOP Strap 2.0 to measure sleep quantity and sleep quality in ambulatory subjects. We will measure sleep by both WHOOP Strap 2.0 and PSG in healthy volunteers (age 18 - 45 years) without self-reported sleep disorders or chronic disabling medical conditions.

In ambulatory patients, sleep is usually assessed by the American Academy of Sleep Medicine guidelines which derives from the Rechtschaffen and Kales (R&K) method with good to excellent inter-observer reliability for assessing sleep in the same population; but the Cohen's K range is still 0.68 to 0.82 and much lower for non rapid eye movement (NREM) sleep stage 1 (N1). To account for such inter- and intra-rater reliability issues with the PSG gold-standard, we will only consider sleep stages that are unequivocally scored as a particular stage (light NREM, slow wave sleep [SWS] or REM sleep [R sleep]) by two different observers.

Additionally, while there are many devices available to healthy individuals to measure heart rate, there aren't many available that provide a daily heart rate variability statistic. Heart rate variability can be defined as the variation over time of the period between consecutive heart beats. This is due to the balancing regulation effects of the parasympathetic (PNS) and sympathetic (SNS) actions of the autonomic nervous system (ANS). Increased SNS action results in a "fight or flight" response, leading to an accelerated heart rate, while increased PNS activity results in a "rest and digest" response, leading to a decelerated heart rate. The increased variability of heart rate (HR) is an indication of the ANS' control on HR and the heart's ability to respond. WHOOP Strap 2.0 provides users with real-time HR and a daily HRV statistic that is included in other variables calculated measuring daily strain and recovery statistics. We will measure HR and HRV by both WHOOP Strap 2.0 and EKG leads in healthy volunteers (ages 18-45 years) without chronic disabling medical conditions.

Inclusion Criteria:

• Ability to provide informed consent
• Willingness to undergo a polysomnography electrode hook-up and wear a WHOOP strap 2.0.
• Healthy volunteers

Exclusion Criteria:

• Presence of untreated sleep disorder that requires diagnostic testing and treatment (insomnia, obstructive sleep apnea, narcolepsy, restless leg syndrome, REM sleep behavior disorder, or circadian rhythm sleep disorders).
• Apnea-Hypopnea index greater than or equal to 15 per hour as per AASM guidelines
• Active substance abuse or alcoholism
• Pregnancy or lactation
• Currently taking sedative medications
• Chronic medical conditions such as hypertension, diabetes mellitus, cardiac disorders, arthritis, or other chronic medical conditions
• BMI greater than 26