Zephyr BioHarness Research Articles

Measurement of respiratory rate with cardiac belt: Metrological characterization

The rapid growth of available wearable technologies, particularly in the healthcare sector, has ushered in a new era of digital health. This progress has introduced new possibilities for the monitoring of vital signs, including breathing rate (BR). BR is a crucial health parameter used to assess an individual's overall well-being; specifically, it can be considered a precise indicator of pathological conditions and stressors. The aim of this study is to conduct a metrological characterization of one of the most widely used BR sensors for the measurement of BR (i.e., Zephyr BioHarness 3.0), comparing it to a BR gold standard monitor (i.e., a spirometer), in determined test conditions, including both natural and defined BR patterns. Additionally, the Monte Carlo method (MCM) was applied to evaluate the propagation of the measurement uncertainty in the identification of the peaks of respiratory signal, used to calculate BR. Results reveal that the Zephyr BioHarness 3.0 sensor provides highly accurate BR measurements, with a precision of ±1 bpm. Bland-Altman analysis indicates a 95 % confidence interval of [-2; 3] bpm, demonstrating a close agreement with the reference instrument. The Pearson's correlation coefficient of 0.95 further validates the linear correlation between the reference/test measurements. The simulation based on MCM provides an expanded uncertainty of ±2 bpm (coverage factor k = 2) in BR estimation due to the uncertainty in the peaks identification (compatible with the accuracy provided by the manufacturer). These results highlight the Zephyr BioHarness 3.0 sensor reliability for BR monitoring while emphasizing the significance of accounting for different disturbing factors, e.g., uncertainty in peak detection during data analysis, also to provide a rigorous level of confidence in the measurement results, hence being able to properly interpret them in biomedical applications.

Assessment of Heart Rate Monitoring During Exercise With Smart Wristbands and a Heart Rhythm Patch: Validation and Comparison Study.

The integration of wearable devices into fitness routines, particularly in military settings, necessitates a rigorous assessment of their accuracy. This study evaluates the precision of heart rate measurements by locally manufactured wristbands, increasingly used in military academies, to inform future device selection for military training activities. This research aims to assess the reliability of heart rate monitoring in chest straps versus wearable wristbands. Data on heart rate and acceleration were collected using the Q-Band Q-69 smart wristband (Mobile Action Technology Inc) and compared against the Zephyr Bioharness standard measuring device. The Lin concordance correlation coefficient, Pearson product moment correlation coefficient, and intraclass correlation coefficient were used for reliability analysis. Participants from a Northern Taiwanese medical school were enrolled (January 1-June 31, 2021). The Q-Band Q-69 demonstrated that the mean absolute percentage error (MAPE) of women was observed to be 13.35 (SD 13.47). Comparatively, men exhibited a lower MAPE of 8.54 (SD 10.49). The walking state MAPE was 7.79 for women and 10.65 for men. The wristband's accuracy generally remained below 10% MAPE in other activities. Pearson product moment correlation coefficient analysis indicated gender-based performance differences, with overall coefficients of 0.625 for women and 0.808 for men, varying across walking, running, and cooldown phases. This study highlights significant gender and activity-dependent variations in the accuracy of the MobileAction Q-Band Q-69 smart wristband. Reduced accuracy was notably observed during running. Occasional extreme errors point to the necessity of caution in relying on such devices for exercise monitoring. The findings emphasize the limitations and potential inaccuracies of wearable technology, especially in high-intensity physical activities.

Accuracy of heart rate measured by military-grade wearable ECG monitor compared with reference and commercial monitors

IntroductionPhysiological monitoring of soldiers can indicate combat readiness and performance. Despite demonstrated use of wearable devices for HR monitoring, commercial options lack desired military features. A newly developed OMNI monitor...

Frailty Syndrome as a Transition from Compensation to Decompensation: Application to the Biomechanical Regulation of Gait.

Most gait parameters decrease with age and are even more importantly reduced with frailty. However, other gait parameters exhibit different or even opposite trends for aging and frailty, and the underlying reason is unclear. Literature focuses either on aging, or on frailty, and a comprehensive understanding of how biomechanical gait regulation evolves with aging and with frailty seems to be lacking. We monitored gait dynamics in young adults (19-29 years, n = 27, 59% women), middle-aged adults (30-59 years, n = 16, 62% women), and non-frail (>60 years, n = 15, 33% women) and frail older adults (>60 years, n = 31, 71% women) during a 160 m walking test using the triaxial accelerometer of the Zephyr Bioharness 3.0 device (Zephyr Technology, Annapolis, MD, USA). Frailty was evaluated using the Frail Scale (FS) and the Clinical Frailty Scale (CFS). We found that in non-frail older adults, certain gait parameters, such as cadence, were increased, whereas other parameters, such as step length, were decreased, and gait speed is maintained. Conversely, in frail older adults, all gait parameters, including gait speed, were decreased. Our interpretation is that non-frail older adults compensate for a decreased step length with an increased cadence to maintain a functional gait speed, whereas frail older adults decompensate and consequently walk with a characteristic decreased gait speed. We quantified compensation and decompensation on a continuous scale using ratios of the compensated parameter with respect to the corresponding compensating parameter. Compensation and decompensation are general medical concepts that can be applied and quantified for many, if not all, biomechanical and physiological regulatory mechanisms of the human body. This may allow for a new research strategy to quantify both aging and frailty in a systemic and dynamic way.

Wearable Electrocardiography for Physical Activity Monitoring: Definition of Validation Protocol and Automatic Classification

Wearable devices are rapidly spreading thanks to multiple advantages. Their use is expanding in several fields, from medicine to personal assessment and sport applications. At present, more and more wearable devices acquire an electrocardiographic (ECG) signal (in correspondence to the wrist), providing potentially useful information from a diagnostic point of view, particularly in sport medicine and in rehabilitation fields. They are remarkably relevant, being perceived as a common watch and, hence, considered neither intrusive nor a cause of the so-called "white coat effect". Their validation and metrological characterization are fundamental; hence, this work aims at defining a validation protocol tested on a commercial smartwatch (Samsung Galaxy Watch3, Samsung Electronics Italia S.p.A., Milan, Italy) with respect to a gold standard device (Zephyr BioHarness 3.0, Zephyr Technology Corporation, Annapolis, MD, USA, accuracy of ±1 bpm), reporting results on 30 subjects. The metrological performance is provided, supporting final users to properly interpret the results. Moreover, machine learning and deep learning models are used to discriminate between resting and activity-related ECG signals. The results confirm the possibility of using heart rate data from wearable sensors for activity identification (best results obtained by Random Forest, with accuracy of 0.81, recall of 0.80, and precision of 0.81, even using ECG signals of limited duration, i.e., 30 s). Moreover, the effectiveness of the proposed validation protocol to evaluate measurement accuracy and precision in a wide measurement range is verified. A bias of -1 bpm and an experimental standard deviation of 11 bpm (corresponding to an experimental standard deviation of the mean of ≈0 bpm) were found for the Samsung Galaxy Watch3, indicating a good performance from a metrological point of view.

Effects of a Modern Virtual Reality 3D Head-Mounted Display Exergame on Simulator Sickness and Immersion Under Specific Conditions in Young Women and Men: Experimental Study.

Many young adults do not reach the World Health Organization's minimum recommendations for the amount of weekly physical activity. The virtual reality 3D head-mounted display (VR 3D HMD) exergame is a technology that is more immersive than a typical exercise session. Our study considers gender differences in the experience of using VR games for increasing physical activity. The aim of this study was to examine the differences in the effects of VR 3D HMD gaming in terms of immersion, simulator sickness, heart rate, breathing rate, and energy expenditure during two 30-minute sessions of playing an exergame of increasing intensity on males and females. To examine the effects of the VR 3D HMD exergame, we experimented with 45 participants (23 males and 22 females) exercising with VR 3D HMD Oculus Quest 1, hand controllers, and Zephyr BioHarness 3.0. Players exercised according to the Audio Trip exergame. We evaluated the immersion levels and monitored the average heart rate, maximum heart rate, average breathing rate, maximum breathing rate, and energy expenditure in addition to simulator sickness during two 30-minute exergame sessions of increasing intensity. Audio Trip was well-tolerated, as there were no dropouts due to simulator sickness. Significant differences between genders were observed in the simulator sickness questionnaire for nausea (F2,86=0.80; P=.046), oculomotor disorders (F2,86=2.37; P=.010), disorientation (F2,86=0.92; P=.040), and total of all these symptoms (F2,86=3.33; P=.04). The measurements after the first 30-minute VR 3D HMD exergame session for all the participants showed no significant change compared to the measurements before the first 30-minute exergame session according to the total score. There were no gender differences in the immersion (F1,43=0.02; P=.90), but the measurements after the second 30-minute exergame session showed an increase in the average points for immersion in women and men. The increase in the level of immersion in the female group was higher than that in the male group. A significant difference between genders was observed in the average breathing rate (F2,86=1.44; P=.04), maximum breathing rate (F2,86=1.15; P=.047), and energy expenditure (F2,86=10.51; P=.001) measurements. No gender differences were observed in the average heart rate and maximum heart rate measurements in the two 30-minute sessions. Our 30-minute VR 3D HMD exergame session does not cause simulator sickness and is a very immersive type of exercise for men and women users. This exergame allows reaching the minimum recommendations for the amount of weekly physical activity for adults. The second exergame session resulted in simulator sickness in both groups, more noticeably in women, as reflected in the responses in the simulator sickness questionnaire. The gender differences observed in the breathing rates and energy expenditure measurements can be helpful when programming VR exergame intensity in future research.

Assessing the Impact of Work Activities on the Physiological Load in a Sample of Loggers in Sicily (Italy).

Occupational logging activities expose workers to a wide range of risk factors, such as lifting heavy loads, prolonged, awkward positioning of the lower back, repetitive movements, and insufficient work pauses. Body posture has an important impact on the level of physiological load. The present study involved a group of 40 loggers in the province of Enna (Sicily, Italy) with the aim of defining the impact of logging activities on the workers’ physiological strain during the three primary work tasks of felling, delimbing, and bucking. The Zephyr Bioharness measurement system was used to record trunk posture and heart rate data during work tasks. The NASA TLX questionnaire was used to explore workers’ effort perception of the work tasks. Based on our results, the most demanding work task was tree felling, which requires a higher level of cardiac cost and longer periods spent in awkward trunk postures. The perceived physiological workload was consistently underestimated, especially by the more experienced loggers. Lastly, as the weight of the chainsaw increased, the cardiac load increased.

Estimation of Tidal Volume during Exercise Stress Test from Wearable-Device Measures of Heart Rate and Breathing Rate

Tidal volume (TV), defined as the amount of air that moves in or out of the lungs with each respiratory cycle, is important in evaluating the respiratory function. Although TV can be reliably measured in laboratory settings, this information is hardly obtainable under everyday living conditions. Under such conditions, wearable devices could provide valuable support to monitor vital signs, such as heart rate (HR) and breathing rate (BR). The aim of this study was to develop a model to estimate TV from wearable-device measures of HR and BR during exercise. HR and BR were acquired through the Zephyr Bioharness 3.0 wearable device in nine subjects performing incremental cycling tests. For each subject, TV during exercise was obtained with a metabolic cart (Cosmed). A stepwise regression algorithm was used to create the model using as possible predictors HR, BR, age, and body mass index; the model was then validated using a leave-one-subject-out cross-validation procedure. The performance of the model was evaluated using the explained variance (R2), obtaining values ranging from 0.65 to 0.72. The proposed model is a valid method for TV estimation with wearable devices and can be considered not subject-specific and not instrumentation-specific.

Five-Year PTSD Symptom Remission in Two Patients Following Treatment With Rivastigmine.

The beneficial effect of rivastigmine, an acetylcholinesterase inhibitor (AChEi), which increases levels of acetylcholine (ACh), was first reported in 2013. This paper replicates those findings and reports sustained symptom remission. The high-frequency (HF) component of heart rate variability (HRV) is a measure of cholinergic withdrawal and was measured using a Zephyr Bioharness HR monitor, pre- and post-commencement of treatment. Data analysis was performed using Kubios HRV software. PTSD symptom severity was assessed using the Post-Traumatic Checklist-Civilian (PCL-C). Low HF HRV was observed in both patients before rivastigmine treatment and reductions in PCL-C scores paralleled increases in HF HRV values. Follow-up revealed low HF HRV values in both patients despite PCL-C scores indicating remission. Sympathetic nervous system hyperactivity was observed in one patient, just before a suicide attempt. Following rivastigmine treatment, the patient had no further suicidal ideation or attempts. Another patient reported worsening of her PTSD symptoms in the peri-menstrual period, which was abolished by rivastigmine. She also experienced symptom relapse following prolonged infections. Low HF HRV has been reported in PTSD patients, but findings have been inconsistent. Cholinergic withdrawal could explain the disturbances in sleep, learning, and memory seen in PTSD patients. The relapse of symptoms following prolonged infection implicates the immune system as a possible initiator of the disorder. ACh and estrogen have anti-inflammatory properties, supporting a possible role of inflammation in initiating PTSD. The effect of rivastigmine treatment should be tested in properly controlled clinical trials.

Real-Time Quality Index to Control Data Loss in Real-Life Cardiac Monitoring Applications.

Wearable cardiac sensors pave the way for advanced cardiac monitoring applications based on heart rate variability (HRV). In real-life settings, heart rate (HR) measurements are subject to motion artifacts that may lead to frequent data loss (missing samples in the HR signal), especially for commercial devices based on photoplethysmography (PPG). The current study had two main goals: (i) to provide a white-box quality index that estimates the amount of missing samples in any piece of HR signal; and (ii) to quantify the impact of data loss on feature extraction in a PPG-based HR signal. This was done by comparing real-life recordings from commercial sensors featuring both PPG (Empatica E4) and ECG (Zephyr BioHarness 3). After an outlier rejection process, our quality index was used to isolate portions of ECG-based HR signals that could be used as benchmark, to validate the output of Empatica E4 at the signal level and at the feature level. Our results showed high accuracy in estimating the mean HR (median error: 3.2%), poor accuracy for short-term HRV features (e.g., median error: 64% for high-frequency power), and mild accuracy for longer-term HRV features (e.g., median error: 25% for low-frequency power). These levels of errors could be reduced by using our quality index to identify time windows with few or no data loss (median errors: 0.0%, 27%, and 6.4% respectively, when no sample was missing). This quality index should be useful in future work to extract reliable cardiac features in real-life measurements, or to conduct a field validation study on wearable cardiac sensors.

Feasibility Assessment of Wearable Respiratory Monitors for Ambulatory Inhalation Topography.

Background: Natural environment inhalation topography provides useful information for toxicant exposure, risk assessment and cardiopulmonary performance. Commercially available wearable respiratory monitors (WRMs), which are currently used to measure a variety of physiological parameters such as heart rate and breathing frequency, can be leveraged to obtain inhalation topography, yet little work has been done. This paper assesses the feasibility of adapting these WRMs for measuring inhalation topography. Methods: Commercially available WRMs were compiled and assessed for the ability to report chest motion, data analysis software features, ambulatory observation capabilities, participant acceptability, purchasing constraints and affordability. Results: The following WRMs were found: LifeShirt, Equivital EQ02 LifeMonitor, Smartex WWS, Hexoskin Smart Garment, Zephyr BioHarness, Nox T3&A1, BioRadio, SleepSense Inductance Band, and ezRIP & zRIP Durabelt. None of the WRMs satisfied all six assessment criteria in a manner enabling them to be used for inhalation topography without modification and development. Conclusions: The results indicate that there are WRMs with core technologies and characteristics that can be built upon for ambulatory inhalation topography measurement in the NE.

A Single Session of Heart Rate Variability Biofeedback Produced Greater Increases in Heart Rate Variability Than Autogenic Training.

Heart rate variability biofeedback (HRV-BF) has been confirmed to increase heart rate variability (HRV) and cardiac outflows by baroreflex in healthy populations and clinical patients. Autogenic training (AT) is common used in the psychological intervention. This study integrates a single-session of HRV-BF and AT into a high-technology mobile application (app), and examines the effects on HRV indices, breathing rates, and subjective relaxation scores. Healthy college students were recruited and assigned to the single-session HRV-BF group or AT group. Participants in the HRV-BF group received HRV-BF combined with paced breathing training, which gradually stepped down their breathing rates from 12, to 8, to 6 breaths/per min; and received feedback of HRV indices from the app. Participants in the AT group received autogenic training and feedback of heart rate from the app. A chest belt Zephyr BioHarness was connected through Bluetooth to a Zenfone5 mobile phone, it collected the signals of interbeat intervals and breathing rates at pre-training, mid-training, and post-training stages. The Kubios HRV software was used to analyze HRV indices. The results reveal higher HRV indices and lower breathing rates during mid-training and post-training in the HRV-BF group compared to the AT group. There were higher high-frequency of HRV at post-training than pre-training in the AT group. Participants of both groups increased their subjective relaxation scores after training. The HRV-BF protocol increased cardiac outflows by baroreflex and decreased breathing rates, and the AT protocol increased high-frequency of HRV. These high-technology wearable devices combined with psychological interventions will apply to various populations in the future.

Test and Evaluation of Heart Rate Derived Core Temperature Algorithms for Use in NCAA Division I Football Athletes.

The purpose of this study was to assess the validity of utilizing heart rate to derive an estimate of core body temperature in American Football athletes. This was evaluated by combining commercially available Zephyr Bioharness devices, which includes an embedded estimated core temperature (ECT) algorithm, and an ingestible radio frequency core temperature pill during the highest heat injury risk timepoint of the season, summer training camp. Results showed a concordance of 0.643 and 78% of all data points fell within +/−1.0 °F. When the athletes were split into Upper (>/=6.0%) and Lower (<6.0%) body composition groups, there was a statistical improvement in accuracy with the Upper Body Fat% reaching 0.834 concordance and 93% of all values falling within +/−1.0 °F of the Gold Standard. Results suggest that heart rate derived core temperature assessments are a viable tool for heat stress monitoring in American football, but more work is required to improve on accuracy based on body composition.

Predicting Sports Injuries with Wearable Technology and Data Analysis

Injuries resulting from sports and physical activities can be persistent and pose a substantial problem for player’s economic wellbeing and quality of life. Wearable technologies in conjunction with analytics can help mitigate the risk to players by identifying injury risk factors and focusing on risk reduction. Prior to engaging in strenuous sport activities, wearables can be employed to facilitate the quantification of relevant functional capabilities, ultimately advancing the field of sports injury management. In this paper, we discuss how wearable technologies can improve the health and athletic performance of athletes by monitoring participants across many variables. A cohort of 54 army ROTC cadets participated in this study. Using Zephyr BioHarness Wearable technology, we gathered quantifiable data to generate insights that allow us to predict and prevent injuries related the wearer’s physical exertion during sporting activities. This study finds that a combination of high BMI and high mechanical loads could result in injury. Therefore, in creating an exercise program, it is imperative to ensure that mechanical load is incrementally increased through the practice season as athletes become conditioned. While, a high level repetitious mechanical load with unconditioned athletes could cause injuries in short time, it is important to impose enough mechanical loads in the training program to ensure good musculoskeletal development. While our analyses identified several factors associated with injury data during ROTC activities, other wearable variables might become significant in other situations. In summary, results from this study demonstrate that wearable technology allows players with an increased risk of injury to be identified and targeted for intervention.

Faster Heart Rate Recovery Correlates With High-Intensity Match Activity in Female Field Hockey Players-Training Implications.

Harry, K and Booysen, MJ. Faster heart rate recovery correlates with high-intensity match activity in female field hockey players-training implications. J Strength Cond Res 34(4): 1150-1157, 2020-The physical match demands of female field hockey are intense and may differ according to playing positions. In addition, conducting sports-specific field tests can assist coaches in determining their players' preparedness for competition. There is limited research regarding the match demands and relevance of field testing at premier league levels. Therefore, the aims were to describe the physical match demands of female premier league (amateur) field hockey, and to determine the relationships between match activity patterns and physical performance tests. Match activity and heart rate data were collected from 32 female participants using the Zephyr BioHarness 3 system. Participants also performed the Yo-Yo intermittent recovery (level 1) (n = 22), repeated sprint ability (n = 21), and the heart rate recovery (n = 16) tests. Moderate to large effect sizes were observed when defenders were compared with midfielders and forwards for time spent (%) in standing/walking and jogging (d = 0.64-1.30) in addition to the playing time (%) spent in the low-to-moderate and very high heart rate zones (d = 0.69-0.85). Heart rate recovery (10 s) correlated with the playing time (%) spent in sprinting (r = 0.73, p = 0.002). Heart rate recovery (60 s) and the Yo-Yo intermittent recovery test both correlated with the playing time (%) spent in running (r = 0.77, p = 0.0006 and r = 0.54, p = 0.01). The differences in physical match demands between positions emphasize the importance of training specificity at premier league levels. The heart rate recovery test can be used to assess a female field hockey player's capability to perform high-intensity match activity.

Minimal Detectable Change Thresholds and Responsiveness of Zephyr Bioharness and Fitbit Charge Devices.

Nazari, G and MacDermid, JC. Minimal detectable change thresholds and responsiveness of zephyr bioharness and Fitbit Charge devices. J Strength Cond Res 34(1): 257-263, 2020-The aim of the current study was to define the minimal detectable change (MDC) thresholds for Zephyr Bioharness (ZB) and Fitbit Charge Heart Rate (FC-HR) variables and to establish the internal responsiveness of ZB and FC-HR devices in terms of their HR, respiratory rate variables, and number of steps taken variables, in a healthy sample of men and women at resting, submaximal activity and throughout recovery phases. A total of sixty participants (30 women, 48 ± 15) and (30 men, 48 ± 15) were recruited using stratified convenience and snowball sampling approaches from our university student, staff, and faculty population. At rest, MDC90 values of ±4.89 and ±5.15 were noted for ZB and FC-HR devices, respectively. Throughout the recovery, thresholds of ±8.14 for ZB and 8.74 for FC-HR were reported. During the submaximal phases, scores of ±8.18 and ±9.35 were established for ZB and FC-HR, respectively. From a resting to a submaximal state, the standardized response means (SRMs) for ZB and FC-HR variables exhibited large responsiveness of SRMZB-HR = 4.42; SRMFC-HR = 4.04. In addition, the ZB respiratory rate variable showed the largest effect size of SRMZB-RR = 2.55. Similarly, the large effect size of SRMFC-ST = 1.76 was reported for the FC-HR steps taken variable. From a submaximal to a recovery state, the SRMs for ZB and FC-HR variables demonstrated effect sizes of SRMZB-HR = -3.10; SRMFC-HR = -3.12. Furthermore, the ZB respiratory rate variable displayed similar internal responsiveness measures of SRMZB-RR = -2.45. To conclude, Similar MDC HR thresholds can be expected using the ZB and FC-HR devices and that the two devices demonstrated large internal responsiveness in our healthy male and female cohort when transitioning from resting to submaximal states and vice-versa. Our findings suggest that the ZB and FC-HR devices can be used in monitoring performance improvements or deterioration over time and would allow qualified personnel in assessing the effectiveness of exercise programs in healthy individuals.

Reliability of Zephyr BioHarness Respiratory Rate at Rest, During the Modified Canadian Aerobic Fitness Test and Recovery.

Nazari, G and MacDermid, JC. Reliability of Zephyr BioHarness respiratory rate at rest, during the modified Canadian Aerobic Fitness Test and recovery. J Strength Cond Res 34(1): 264-269, 2020-Technological innovations have led to the development of wearable physiological monitoring devices, such as the Zephyr BioHarness (ZB). It is necessary to establish the measurement properties of a device and to determine its reliability parameters, before its utilization. The purpose of current study was to determine the test-retest reliability of ZB respiratory rate variable at rest, during the modified Canadian Aerobic Fitness Test (mCAFT) (a submaximal test) and throughout recovery. Stratified convenience and snowballing were used to recruit 60 participants (30 females). Respiratory rate reliability was assessed at rest, with total of 20 measurements, during the mCAFT with total of 24 measures and throughout the recovery with total of 20 measures between the first and second sessions. At rest, test-retest respiratory rate intraclass correlation coefficients (ICCs) and SEM for ZB ranged from 0.76 to 0.84 (0.62-0.83). During the mCAFT, the ZB ICCs and (SEM) ranged from 0.76 to 0.89 (1.53-4.00). Throughout the recovery, the ICCs and SEM ranged from 0.79 to 0.90 (0.90-1.28). To conclude, ZB respiratory rate variable demonstrated excellent reliability measures in a large sample of healthy male and female individuals across different age groups at rest, during a submaximal activity and throughout recovery. Our study findings add to the existing pool of literature regarding the reliability parameters of ZB wearable device and propose that stable and consistent measures of respiratory rate can be obtained using ZB device among healthy male and female participants at rest, during submaximal activity (mCAFT) and throughout recovery.

Inter-Instrument Reliability and Agreement of Fitbit Charge Measurements of Heart Rate and Activity at Rest, during the Modified Canadian Aerobic Fitness Test, and in Recovery.

Purpose: We determined the inter-instrument reliability and agreement parameters of the Fitbit Charge Heart Rate (Charge HR) device during three phases: rest, modified Canadian Aerobic Fitness Test (mCAFT), and recovery. Method: We recruited 60 participants for this cross-sectional measurement study using convenience and snowball sampling approaches. The performance of the Charge HR was assessed throughout the rest, mCAFT, and recovery phases. To establish inter-instrument reliability, the Charge HR variables - heart rate, steps taken, and energy expenditures - were compared with those for two other devices: the Zephyr BioHarness (ZB) for heart rate and the Fitbit One for steps taken and energy expenditure. Measurements were recorded every 30 seconds. Results: At rest, the inter-instrument intra-class correlation coefficient (ICC) (standard error of measurement [SEM]) for the Charge HR versus the ZB was ≥ 0.97 (range, min-max, 1.02-1.32). During the mCAFT and in recovery, the ICCs (SEMs) for the Charge HR and the ZB were ≥ 0.89 (range, min-max, 1.30-3.98) and ≥ 0.68 (range, min-max, 3.58-8.35), respectively. During the mCAFT only, the number of steps taken and the energy expenditure recorded by the Charge HR and the Fitbit One displayed ICCs (SEMs) of 0.97 (83.00) and 0.77 (14.70), respectively. The average agreement differences in heart rate in this pair-wise device comparison indicated mean differences of -0.20, 4.00, and 1.00 beats per minute at rest, during the mCAFT, and in recovery, respectively. Conclusions: The Charge HR heart rate variable demonstrated excellent inter-instrument reliability compared with the ZB and provided good levels of agreement. The steps taken and energy expenditure variables displayed excellent reliability measures between Charge HR and Fitbit One. Our findings may be used to capture field-based wireless measures of heart rate in various phases and provide information about possibly using the Charge HR and ZB devices interchangeably.

Deep ECG-Respiration Network (DeepER Net) for Recognizing Mental Stress.

Unmanaged long-term mental stress in the workplace can lead to serious health problems and reduced productivity. To prevent this, it is important to recognize and relieve mental stress in a timely manner. Here, we propose a novel stress detection algorithm based on end-to-end deep learning using multiple physiological signals, such as electrocardiogram (ECG) and respiration (RESP) signal. To mimic workplace stress in our experiments, we used Stroop and math tasks as stressors, with each stressor being followed by a relaxation task. Herein, we recruited 18 subjects and measured both ECG and RESP signals using Zephyr BioHarness 3.0. After five-fold cross validation, the proposed network performed well, with an average accuracy of 83.9%, an average F1 score of 0.81, and an average area under the receiver operating characteristic (ROC) curve (AUC) of 0.92, demonstrating its superiority over conventional machine learning models. Furthermore, by visualizing the activation of the trained network’s neurons, we found that they were activated by specific ECG and RESP patterns. In conclusion, we successfully validated the feasibility of end-to-end deep learning using multiple physiological signals for recognition of mental stress in the workplace. We believe that this is a promising approach that will help to improve the quality of life of people suffering from long-term work-related mental stress.

Abstract P099: Heart Rate Variability Differences Between Green and Suburban Walking: A Pilot Crossover Study

Introduction: Heart rate variability (HRV) assesses the sympathetic and parasympathetic innervation of the heart. Lower HRV indicates greater sympathetic tone and is associated with adverse cardiovascular outcomes. During exercise, factors like activity intensity influence HRV. Yet, an environment’s inherent anxiety-/stress-promoting characteristics may also affect HRV. Hypothesis: Given nature’s calming characteristics, we hypothesized green (i.e., nature-based) walking would promote higher HRV and less HRV reduction than suburban walking. Methods: Twenty-four middle-aged adults (20 female; 49.3 ± 6.7 yrs; BMI: 30.7 ± 7.9 kg/m 2 ) participated in this nine-week crossover study comprised of once-weekly 50-minute moderate-intensity walking sessions. Participants walked for three weeks in each of two treatment conditions: (1) green walking: nature-based walking on trails of local arboretum; and (2) suburban walking: walking on sidewalks of a local suburb’s downtown area. Half were assigned to suburban walking in the first treatment period, and half completed green walking first. A two-week washout separated treatments. The Zephyr BioHarness 3 assessed HRV—reported as standard deviations of normal-to-normal RR intervals in milliseconds (ms) while also tracking activity intensity. For analysis, walks were split into 15-minute intra-walk phases with the first, second, and third phases representing each walk’s beginning, middle, and end. Five-minute pre- and post-walk sitting phases for HRV were also created. Linear mixed models with repeated measures evaluated HRV phase differences between treatments and HRV change between phases by treatment. Results: Lower HRV was observed during the pre-walk sitting phase in the green (56.5 ms) vs. the suburban walking treatment (62.4 ms; p = 0.04); however, a sequence effect was present ( p = 0.02). Due to lower walking intensity during green walking (0.31 g vs. 0.27 g; p &lt; 0.01), activity intensity was a covariate in all intra-walk analyses. Intra-walk phase analyses revealed higher green vs. suburban walking HRV during the second (29.1 ms vs. 24.2 ms, respectively; p &lt; 0.01) and third (33.9 ms vs. 23.8 ms, respectively; p = 0.03) phases. Further, less HRV reduction was seen between the first and second intra-walk phases during green (-7.6 ms) vs. suburban walking (-12.4 ms; p = 0.05). Between-treatment HRV differences were not found for the post-walk sitting phase. No sequence effects were observed for the intra-walk or post-walk phases. Finally, no carryover effects were observed—suggesting adequate washout between treatments. Conclusions: Green walking elicits higher HRV and less HRV reduction vs. suburban walking. Activity intensity did not explain these observations. Fully powered longer-term trials should rigorously evaluate green walking’s potential anxiety-/stress-reducing characteristics.