Basic characteristics of participants (n = 20).

Wrist-worn activity monitors, such as smartwatches, are frequently used to monitor energy expenditure (EE) of physical activity, but there is a high degree of heterogeneity in their accuracy. The purpose of this study was to evaluate the validity of four affordable, low-price smartwatches, including HONOR Band 7 (HNB7), HUAWEI Band 8 (HWB8), XIAOMI Smart Band 8 (XMB8), and KEEP Smart Band B4 Lite (KPB4L), for estimating EE during ergometer cycling in untrained Chinese women. Twenty Chinese women who exercised ≤3 times per week simultaneously wore two smartwatches, randomly assigned to each wrist, during cycling at 30W, 40W, 50W and 60W on the ergometer. As the golden standard, indirect calorimetry (CORTEX METAMAX 3B, MM3B) was used to evaluate EE at the same time. For all loads, EE values were significantly overestimated by XMB8 and KPB4L, compared to the golden standard (all p