## 4 Discussion  
Due to the increased interest of children and adolescents in modern technologies and wearable devices, the purpose of this review was to examine whether commercially available wearable devices have an impact on physical activity and health in children and adolescents. In 11 studies, the authors used four different commercially available wrist-wearable activity devices. In general, wearable technology may be used as a motivating tool to enhance PA behaviors and evaluate PA programs, in accordance with previous research [30,32]. Only two studies were not able to identify an increase in PA in children and adolescents [31,32]. Different questionnaires that were modified for children, their parents, and teachers were used to assess PA motivation [25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35]. The findings indicate that technology promoting a healthy lifestyle may cause negative motivation and autonomous motivation for PA and a decrease in changes in MVPA after wearing the Fitbit. These motivational results have been attributed to aspects of the Fitbit that interfere with pupils' basic psychological needs [31]. The decrease in autonomous motivation may have contributed to the decrease in MVPA, according to self-determination theory [36]. In a large number of the included studies, an increased motivation for physical activity has been observed after using pedometers or accelerometers. The analysis of the obtained results shows an increase in daily steps, the daily average of MVPA, daily PA, RAW-PA acceptability, usefulness, ease of use, and motivation among adolescents [26, 27, 28, 29, 30, 34, 35]. In one of the studies [25], the average daily step count and degree of usual MVPA did not show any changes. In the second study [33], the daily average of MVPA in the adopters group demonstrated improvement, but there were no changes in the preadopters group. The inactive teen girls became more conscious of their physical activity thanks to activity monitors and apps, which also assisted them in setting objectives and motivated them to walk further [27]. Adolescents demonstrated good acceptance of the Raising Awareness of Physical Activity (RAW-PA) program, which aims to increase their physical activity [29]. Numerous behavior-change techniques (BCTs) that have been previously proved to promote adult physical activity (PA) are included in wearable activity trackers. The results have shown that wearable devices are capable of capturing and processing parameters of physical activity such as sleep duration and quality or heart rate. The device automatically calculates parameters such as the length of time spent in the aerobic and anaerobic zones, as well as the duration of physical work at the maximum oxygen consumption level, based on the collected data. Tracking these parameters is important for the good health of young individuals. The use of wearable devices can improve the strength of the cardiovascular and respiratory systems [35]. The findings demonstrate that increasing PA can reverse the child obesity pandemic since children in the intervention group had considerably lower levels of SED and higher levels of total PA than children in the control group [26]. These technologies have shown good results in health promotion programs [28]. Since there are more factors that can be investigated with an accelerometer than a pedometer, they are used more commonly by researchers and in clinical settings. Unlike pedometers, which only track the distance walked by the number of steps, accelerometers allow us to assess the frequency, duration, and intensity of PA [37]. In terms of activity count (number of steps) and energy expenditure in various demographics (healthy and chronically sick populations), both devices demonstrated good validity [38,39]. Vigorous (or greater) physical activity is a stronger predictor of vascular function [40], cardiorespiratory fitness [41, 42, 43, 44], or body fat [45, 46, 47]. There are certain limitations that need to be acknowledged in this systematic review.