Analysis of physiological tremors during different intensities of armcurl exercises using wearable threeaxis accelerometers in healthy young men: a pilot study

[Purpose] The purpose of this pilot study was to determine whether physiological tremors (PTs) assessed using an accelerometer could be used to evaluate resistance exercise intensity. [Methods] Twenty healthy young men with no prior experience of resistance exercise were recruited. Different intensities (resting, 30%, 50%, and 70% of their predetermined one-repetition maximum (1- RM)) of arm-curl exercise were used to elicit PT. The total work was held equally by varying the number of repetitions, with five sets for each intensity. Sessions of varying intensities were performed randomly with a washout period of at least a week. PT responses were recorded during exercise using accelerometers (3-axis) attached to the wrist and ear. Electromyography (EMG) data were obtained from the biceps brachii muscle during exercise. PT and EMG data were expressed as the average root mean square index. [Results] The EMG amplitude increased significantly as exercise intensity increased. Furthermore, PT amplitude significantly increased as exercise intensity increased. Moreover, the Borg rating of perceived exertion (RPE) and lactic acid levels increased significantly. The wrist PT was related to ear PT, EMG, RPE, and lactic acid levels. Additionally, ear PT was associated with EMG, RPE, and lactic acid levels. [Conclusion] This pilot study identified changes in PT during resistance exercise at different intensities. We suggest that the use of PT analyses during these exercises provides a more intuitive delineation of resistanceexercise intensity and fatigue.