Influence Of Skin Color On Sensitivity Of Wrist-worn Technology To Accurately Measure Exertional Heart Rate

As wrist-worn technology continues to gain sophistication, high accuracy of output metrics is imperative to ensure appropriate accessible health data for consumers. Smart watches use light-reflectance photoplethysmography (PPG) to measure HR; however, skin color may influence how light is absorbed and reflected. Exercise modality (body motion), intensity (rapid HR changes), or skin thickness may further affect sensitivity of PPG for HR detection. PURPOSE: Determine the influence of skin color on sensitivity of smart watches to accurately measure exertional HR. METHODS: 209 participants (110 M, 99F; 32.4 ± 11.0 yrs) self-reporting >3dpw of moderate-vigorous physical activity and ability to run one mile in <8 min completed three in-lab exercise protocols: Treadmill ramp (TR), treadmill interval (INT), and cycle ramp (CYC). Participants wore three smart watches with randomized placement and 12-lead ECG throughout exercise. Ultrasound measured skin thickness, and Felix von Luschan score (VLS) quantified skin color into 6 sub-groups. HR data were time synced across devices. Mean absolute percent error (MAPE) between ECG and watch derived HR was calculated for each VLS group and exercise protocol (Table). ANOVA with Bonferroni post hoc determined differences between VLS groups for TR, INT, and CYC with skin thickness as a covariate. RESULTS: With one exception, there were no differences in MAPE across VLS group for TR, INT, or CYC (Table). Smart Watch 1 showed a significant difference between very light (VLS 0-6) and light intermediate (VLS 14-20) groups for INT, with the former experiencing more error (3.0 ± 4.8%) than the latter (1.5 ± 0.8%, p < .01). Skin thickness did not significantly influence these findings (p > .05). CONCLUSION: Skin color does not significantly influence sensitivity of smart watch PPG to measure HR during exercise of varying modalities or intensities. Supported by: This study received funding from Samsung Electronics Co, LTD.