Page 149 - JSOM Summer 2022

an individual’s response and adaptation to training demands, Smart Ring’s sum rank scores were the highest, followed by
overall strain levels, and recovery interventions. Thus, to en- the Fatigue Science Readiband, Whoop strap, and Polar, Bed-
sure accuracy, long-term (24 h) or short-term (5 min) HRV dit, and Garmin devices. 51
recordings are recommended by the Society of Cardiology and
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the North American Society of Pacing and Electrophysiology Kinnunen et al. also highlighted the accuracy of the Oura
Task Force. 57 Smart Ring in measuring HR and HRV. They examined the
accuracy of nocturnal (nighttime) HR and HRV in 54 healthy
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Hinde et al. recently reviewed a variety of physiological volunteer subjects for 49 whole nights. Enhanced nocturnal
monitors. They evaluated 32 wearable devices based on each HRV was previously associated with improved sleep quality
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device’s ability to provide continuous, reliable, and accurate in healthy and clinical patients. This study focused on the
standard HRV parameters in a field setting. They used the importance of standardizing measurements by collecting HR
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following criteria in evaluating the wearable devices: the and HRV measures at night because both actions can be af-
ability to record HRV data continuously, the range of HRV fected by prior activities, time of day, and external stressors
parameters measured, the validity of HRV measures, battery such as noise, outside temperature, and the presence of people.
life, raw data accessibility, the robustness of the device, and The authors suggested that to reduce the effects of these com-
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its suitability for use in a military field setting. They found pounding factors, nighttime measurement of HR and HRV is
that the Polar H10 Heart Rate Sensor delivered better signal appropriate. They found a very high level of agreement be-
quality (99.6%) and had a higher correlation (r = 0.997) com- tween the Oura Smart Ring and the gold standard ECG mea-
pared with a three-lead electrocardiogram (ECG) Holter mon- surements for nocturnal mean HR (r² = 0.996) and HRV (r² =
itor. More importantly, the Polar H10 outperformed the ECG 0.980). Finally, the authors stressed the use of such wearable
Holter during high-intensity exercise, detecting 74 R-R inter- devices for individualized recovery, sleep, and health-related
val errors (99.4% signal quality) compared with R-R interval monitoring: “At present, they (wearables) have enabled highly
errors (89.9% signal quality) from the ECG Holter. Hence, the motivated individual users to adjust their lifestyle and training
authors identified the Polar H10 as the most accurate, reliable, volumes and pay attention to stress factors by following their
and durable wearable device for monitoring continuous HRV ANS responses via changes in their resting HR and HRV.” 53
in a military field setting. 57
Performance tests are the gold standard for assessing NFO/
Omegawave is a noninvasive technology that can be used to OTS because significant decrements in physical performance
assess the internal stress level of a SO, overall readiness to per- over time are critical indicators in the early detection of NFO/
form, and brain function by employing direct current potential OTS. To ensure validity, the physical performance test chosen
and HRV. 58,59 This device consists of a Bluetooth sensor, HR should closely resemble the types of activities the SO routinely
sensor, electrocardiography chest strap, and electrodes that engages in and should be recurring (e.g., post-deployment,
measure cardiac system readiness, ANS readiness, and cen- yearly). Furthermore, establishing baseline performance mea-
tral nervous system readiness within 5 minutes. 58,59 The device sures early in the career of a SO may serve as comparatives
shows robust agreement with a quality-controlled Holter elec- for distinguishing marked changes in individual performance
trocardiogram, with deviations not exceeding 25ms between status. Several maximal performance tests can help distinguish
beat intervals in 95% of the cases. Hence, this technology between NFO and OTS.
is within manageable ranges for clinical practice and sports
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physiology. Omegwave could prove useful for evaluating the Other performance tests that are beneficial in the early detec-
immediate readiness of a SO to perform based on recovery tion of NFO/OTS are the two-bout exercise protocol, which
status from the previous day’s events. requires the individual to perform two consecutive maximal
exercise bouts to volitional fatigue separated by 48 hours of
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Commercial sleep monitoring devices can help track the sleep recovery between tests. The 1.5-mile run test is also help-
and recovery states of SOs, especially during and after high ful because it simulates a maximal test while reducing overall
operational tempo training events and while deployed. How- strain on Operators, is easy to administer, and may even be
ever, sports and exercise medicine practitioners should exercise used for predicting injury risk and training outcomes. Stan-
caution when relying solely on these wearable sleep devices to dard tests used in the military focus on agility, speed, muscular
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accurately track sleep stages. For example, Stone et al. eval- strength, and endurance. However, tests in these domains are
uated the accuracy of eight popular sleep devices, including less suitable because of inconsistent outcomes associated with
6
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the Apple Watch Series 3, Beddit Sleep Monitor 3.0, Fatigue NFO/OTS. Unfortunately, according to Vrijkotte et al., “the
Science Readiband, Fitbit Ionic, Garmin Vivosmart, second- ideal set of tests for early detection of NFO/OTS that can easily
generation Oura Smart Ring, Polar A370, and the Whoop be conducted regularly does not yet exist.” Hence, extensive
Strap 2.0. These sleep-monitoring devices were tested on five investigation is essential within this performance dimension.
study participants for 98 consecutive nights and directly com-
pared with an in-home, previously validated, FDA-approved The Psychological Dimension
electroencephalogram device known as the Sleep Profiler (Ad- Although many of the recovery stress scales described below
vanced Brain Monitoring). They evaluated each device’s accu- require further validation within a SO population, they are val-
racy for measuring total sleep time, total wake time, and sleep idated within elite competitive athletic populations and deserve
efficiency. They observed that a consistent trend for all devices consideration when monitoring recovery status of a SO. Ad-
was their inability to quantify the amount of time the user was ditionally, Nässi et al. recommend that human performance
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awake compared with when they were sleeping. The authors’ practitioners should first “consider the appropriateness of each
final analysis ranked each device’s mean absolute percent error psychological tool in the context of their particular group,
for its total sleep time, total wake time, and sleep efficiency. and regardless of which methods are employed, care should
For this study, they confirmed that the Fitbit Ionic and Oura be taken to employ measurement systematically, provide timely

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