JMIR Publications

ABSTRACT

Background:

Wearable devices that track heart rate variability (HRV) and resting heart rate (RHR) are widely used to gauge physical recovery and readiness. These autonomic signals can be used to monitor and guide an individual’s capacity to meet physical demands. Whether the same signals can be used to track and guide the capacity to meet mental demands is less clear, although theoretical, cross-sectional, and laboratory evidence suggest that HRV may predict cognitive functioning.

Objective:

This study examined whether within-person changes in wearable-derived HRV, RHR, sleep, and physical activity are associated with employees’ self-reported ability to meet the mental demands of their jobs, their mental energy at work, and their work-related stress.

Methods:

A total of 141 employees of a medium-sized US corporation wore a WHOOP biometric capture device and completed weekly surveys on up to 17 consecutive Fridays (July–October 2025), yielding a total of 861 person-weeks. Each survey assessed participants’ perceived ability to meet workplace mental demands, mental energy, and their stress during the preceding week. Wearable metrics (HRV, RHR, sleep duration, sleep consistency, and an intensity-weighted heart-rate zone score) were averaged over the 7 days preceding each survey and decomposed into between-person (participant grand mean) and within-person (weekly deviation from that person mean) components. Bayesian cumulative link mixed models were fit for each predictor–outcome combination, including both components, age, sex, and BMI as fixed effects and a participant-specific random intercept. To control for multiple tests, the critical significance value was set at P<.001.

Results:

Within-person increases in HRV (b=0.256, 99.9% CI 0.018 to 0.494) and decreases in RHR (b=−0.252, 99.9% CI -0.484 to -0.020) were associated with greater reported frequency of meeting workplace mental demands (P’s<.001). Neither autonomic measure was associated with mental energy or stress, although suggestive within-person associations emerged between RHR and energy. Sleep and activity measures revealed no consistent relationships at P<.001, although suggestive within-person associations emerged between sleep duration and energy, between sleep consistency and stress (albeit such that greater consistency was associated with more stress), and between activity levels and energy.

Conclusions:

When employees exhibited higher HRV and lower RHR than their personal average, they reported greater capacity to meet the mental demands of their work. These findings suggest that consumer wearables may capture week-to-week fluctuations in autonomic functioning associated with work-relevant cognitive capacity, raising the possibility of physiologically informed approaches to supporting workforce performance. Clinical Trial: NA