Familiarization session
During the first 2 weeks (Weeks 1–2), the participants attended four familiarization sessions at the gym to get acquainted with the exercise equipment and protocol in their respective groups, including key points of attention in each activity.In the first week, the participants in the barbell group completed six sets of ten repetitions of barbell squats without disks, while the participants in the bodyweight squat group followed the progressive bodyweight training protocol and performed six sets of bodyweight squats. In the second week, the participants were required to attend baseline assessments twice, with intervals of 48 h based on their groups, to determine the starting level of bodyweight squat movement in the bodyweight group and the one-repetition maximum of the barbell squat in the barbell squat group. After the baseline assessments, the lowest values (one repetition maximum and initial squat level) of participants in the two groups were used as the evaluation results to determine the load in the formal intervention. The evaluation approach of bodyweight squat movement level is based on the progressive push-up level assessment used in the research by Kotarsky et al.Forty-eight hours after the 2 weeks of familiarization visits, another baseline assessment of height, weight, body fat, and muscle strength and thickness were conducted in the laboratory of the Beijing Normal University and the Third Hospital at Peking University. The evidence strongly suggests that the 2-week short-term training would not have a significant impact on the physiological indicators of subjectsFrom week 3 (weeks 3–8), all participants started the formal intervention in each experimental condition. The intervention included 60-min sessions separated by at least 48 h, comprising of 15-min warm-up activities (10 activities, 15-min), 30-min squat exercises (6 sets of bodyweight or barbell-squat for each group), and 15-min cool-down exercises (8 activities, 15-min). Both the warming and cool-down exercises were the same in the two experimental groups. All 16 training sessions were supervised by two experienced exercise instructors, and special attention was given to the consistency of the movement pace