Stressing the accuracy: Wrist‐worn wearable sensor validation over different conditions

Abstract

Wearable sensors are promising instruments for conducting both laboratory and ambulatory research in psychophysiology. However, scholars should be aware of their measurement error and the conditions in which accuracy is achieved. This study aimed to assess the accuracy of a wearable sensor designed for research purposes, the E4 wristband (Empatica, Milan, Italy), in measuring heart rate (HR), heart rate variability (HRV), and skin conductance (SC) over five laboratory conditions widely used in stress reactivity research (seated rest, paced breathing, orthostatic, Stroop, speech task) and two ecological conditions (slow walking, keyboard typing). Forty healthy participants concurrently wore the wristband and two gold standard measurement systems (i.e., electrocardiography and finger SC sensor). The wristband accuracy was determined by evaluating the signal quality and the correlations with and the Bland‐Altman plots against gold standard‐derived measurements. Moreover, exploratory analyses were performed to assess predictors of measurement error. Mean HR measures showed the best accuracy over all conditions. HRV measures showed satisfactory accuracy in seated rest, paced breathing, and recovery conditions but not in dynamic conditions, including speaking. Accuracy was diminished by wrist movements, cognitive and emotional stress, nonstationarity, and larger wrist circumferences. Wrist SC measures showed neither correlation nor visual resemblance with finger SC signal, suggesting that the two sites may reflect different phenomena. Future studies are needed to assess the responsivity of wrist SC to emotional and cognitive stress. Limitations and implications for laboratory and ambulatory research are discussed.

Validating Measures of Electrodermal Activity and Heart Rate Variability Derived From the Empatica E4 Utilized in Research Settings That Involve Interactive Dyadic States

“…Examining and visualizing pairs of time-series, collected by both devices simultaneously, allows us to evaluate the E4 more accurately. An exception is a more recent study (Menghini et al, 2019) which focused on stress reactions captured by the E4, while the current study focuses on natural dyadic interactive states.…”

“…Up to now, validation studies have found that the mean IBI data obtained by the E4 is accurate, especially during rest (Ollander et al, 2017;Pietilä et al, 2017;Menghini et al, 2019), and that it is less accurate for HRV (Ollander et al, 2017;Ragot et al, 2018;Menghini et al, 2019), again with higher accuracy during rest (Ollander et al, 2017;Pietilä et al, 2017;Menghini et al, 2019). For example, Menghini et al (2019) report on no correlation between HRV measures derived by the E4 and the same HRV measures derived from the gold standard device during slow walking or keyboard typing (Pearson correlations ranged between 0.00 to 0.07). In contrast, they found nearly perfect correlations between HRV measures during rest (Pearson correlations ranged between 0.97 to 0.98).…”

Assessing the ability of the Fitbit Charge 2 to accurately predict VO2max

“…Despite all subjects running on flat terrain, it would have been more controlled if individual runs were all recorded at a single location. Furthermore, darker skin tones and larger wrist circumferences have been associated with decreased accuracy of wearable devices (21,22), however, these data were not collected. The current study looked at the accuracy of VO 2max estimation by the FBC2 in a group of healthy young men and women; subject race and ethnicity were not reported.…”

Not All Competitions Come to Harm! Competitive Biofeedback to Increase Respiratory Sinus Arrhythmia in Managers

“…Photoplethysmography (PPG) is a more convenient and less invasive alternative to the gold standard electrocardiogram. Several studies have reported that HRV indexes calculated from PPG signal and gold standard electrocardiographic recording are highly correlated ( Lu et al, 2008 , 2009 ; Gil et al, 2010 ; Jeyhani et al, 2015 ; Pinheiro et al, 2016 ; Menghini et al, 2019 ). PPG recordings have satisfactory accuracy in healthy individuals ( Pinheiro et al, 2016 ) during resting conditions in the absence of motion ( Schäfer and Vagedes, 2013 ; Menghini et al, 2019 ).…”