Background. With wrist-worn wearables becoming increasingly available, it is important to understand their reliability and validity in different conditions. The primary objective of this study was to examine the reliability and validity of the Lexin Mio smart bracelet in measuring heart rate (HR) and energy expenditure (EE) in people with different physical activity levels exercising at different intensities. Methods. A total of 65 participants completed one maximal oxygen uptake test and two running exercise tests wearing the Mio smart bracelet, the Polar H10 HR band, and a gas-analysis system. Results. In terms of HR measurement reliability, the Mio smart bracelet showed good reliability in a left versus right test and good test–retest reliability (p > 0.05; mean absolute percentage error (MAPE) < 10%; intraclass correlation coefficient (ICC) > 0.4). For EE measurement, the Mio smart bracelet showed good reliability in a left versus right test, good test–retest reliability on the right (p > 0.05; MAPE > 10%; ICC > 0.4), and low test–retest reliability on the left (p > 0.05; MAPE > 10%; ICC < 0.4). Regarding validity, the Mio smart bracelet showed good validity for HR measurement (p > 0.05; MAPE < 10%; ICC > 0.4) and low validity for EE measurement (p < 0.05; MAPE > 10%; ICC < 0.4). Conclusion. The Lexin Mio smart bracelet showed good reliability and validity for HR measurement among people with different physical activity levels exercising at various exercise intensities in a laboratory setting. However, the smart bracelet showed good reliability and low validity for the estimation of EE.

Background Patellofemoral pain (PFP) syndrome is a common knee joint functional disorder. Blood flow restriction (BFR) training has shown promise in improving PFP; however, the effectiveness of intermittent BFR (iBFR) training remains uncertain. This study aims to compare the rehabilitative effects of iBFR combined with low-load resistance training and high-load resistance training in PFP patients and to assess the effectiveness of iBFR combined with low-load resistance training for improving PFP. Methods and analysis This randomised, patient-assessor blinded, controlled trial will include 42 eligible PFP patients randomly allocated to an intervention group (iBFR combined with low-load resistance training) or a control group (high-load resistance training) in a 1:1 ratio. Participants will receive interventions three times per week for 8 weeks and will be followed up for 24 weeks. The primary outcome measure is pain, and the secondary outcomes include self-reported function, quality of life, muscle strength and muscle thickness. Assessments will be conducted at baseline, 8 weeks and 24 weeks during follow-up. Intention-to-treat analysis will be performed. Collectively, we expect that the findings of this randomised clinical trial will contribute to understanding the potential benefits of iBFR training and provide insightful guidance for developing more effective treatment strategies for patients with PFP. Ethics and dissemination This study was approved by the Sports Science Experiment Ethics Committee of Beijing Sport University (2022274H). Written informed consent will be obtained from all participants. Trial results will be disseminated through peer-reviewed publications. Trial registration number Chinese Clinical Trial Registry (ChiCTR2300068281).

BACKGROUND Wrist-worn wearables have become an increasingly popular way to assess exercise intensity and energy expenditure (EE) in health care and various other settings. However, there is still few research on the validity and reliability of wrist-worn wearables in monitoring exercise parameters at different intensities by people with different levels of physical activity. OBJECTIVE This study assessed the validity and reliability of the Mio Smart Bracelet (Lexin Mio Band 1) in measuring the heart rate (HR) and EE with different physical activity levels during exercise at different intensities. The second objective was to determine if wear position (i.e. dominate or nondominate hand) would cause differences in assessments. METHODS A total of 65 participants (N = 65; 63% female, n = 41; 37% male, n = 24) wore the Lexin smart bracelet (Mio Band 1) and its validity and reliability were assessed against two “gold standard” devices: the Polar H10 heart rate band (for HR) and the gas-analysis system (GAS, Metalyzer 3B) for EE. The participants completed one maximal oxygen uptake (VO2max) test and a running exercise test twice (10-min resting period; 6-min treadmill exercise under three intensities; 10-min recovery period). To measure test-retest reliability, intra-group correlation coefficient (ICC) were determined between the first and second treadmill test. Validity was determined by comparing the Mio with the gold standard (Polar and GAS), using mean differences, mean absolute percentage errors (MAPE), ICC and Bland-Altman analysis. RESULTS For the reliability, the HR consistency between the tests was significant (p < 0.05) in all the states except the Mio in HPAL (P < 0.05), while the EE consistency between the tests, only the right-wrist Mio showed significance in the low-physical-activity level (LPAL) population, and for the moderate-intensity exercise (MIE) and the high-intensity exercise (HIE) in the moderate-physical-activity level (MPAL) population. With regard to the validity, the MAPE between the Polar and the left- and right-wrist Mio bracelets (henceforth “left and right Mios”) ranged from 1% to 7.55%, while the MAPE between the left and right Mios ranged from 10.37% to 32.42%. The HR consistency in the LPAL, MPAL, and high-physical-activity level (HPAL) populations was significant between polar and the left and right Mios at different exercise intensities (P < 0.01), and insignificant only in HPAL group under HIE (P>0.05). As for the EE consistency, it was significant in the left and right Mios under MIE and in the right Mio under HIE in the LPAL group; in the left and right Mios under MIE or HIE, and in the right Mio during recovery in MPAL group; and in the left and right Mios under MIE in the HPAL group (P < 0.05). CONCLUSIONS For HR measurement, the Lexin Mio bracelet showed good reliability and validity among people with different physical activity levels who were exercising under various intensities in a laboratory setting. However, for the estimation of the EE, the Lexin Mio bracelet showed low reliability and validity. CLINICALTRIAL This study was approved by the Experimental Ethics Committee for Sports Science of Beijing Sport University (registration number 2020133H). The participants were informed of the study purpose and procedures and then signed a written informed consent form before enrollment in this study.