This study aims to evaluate the coverage (percentage of usable data) in heart rate (HR) monitoring terms provided by two photoplethysmography(PPG)-based wearable devices during usual office tasks. These two devices are Polar OH1 (armband device) and Maxim MAXREFDES103 (wrist-worn device). A conventional Holter-type monitor (Medicom MTD) was used as reference. 19 healthy patients (9 female and 10 male) were simultaneously monitored with the three devices mentioned above while performing five different office tasks that are usual while doing office work. Each one of these actions was performed during 5 minutes with a 1-minute break between stages. HR was estimated by pulse detection from both wearable devices separately, and the estimates were compared to the HR estimated with the reference ECG device. Obtained results show that the best average coverage across stages (around 70 %) was given by the Polar OH1 device, while a 50 % was obtained by the MAXREFDES103.