Validity and test-retest reliability of a resistance training device for Smith machine back squat exercise

This study evaluated the validity and test-retest reliability of a resistance training device Jueying (Beijing, China) for Smith machine back squat exercise. Twelve male participants completed two test sessions with an interval of one week. In each test session, participants completed 30%, 45%, 60%, and 75% of 1RM back squats on a Smith machine equipped with Jueying and a linear position transducer GymAware (Canberra, Australia), which measured the velocity and power during the movement simultaneously. Results showed that Jueying was both valid (Pearson correlation coefficient [r] = 0.896-0.999, effect size [ES] = 0.004-0.192) when compared with GymAware and consistent between two tests in terms of reliability (intraclass correlation coefficient [ICC] = 0.79-0.95) to assess speed and power within all exercises. The device could be applied to provide athletes and coaches with effective and reliable data in actual application.