Comparison of Two Methods to Measure Snatch and Front Squat Bar Velocity.

Abstract

While bar displacement has traditionally been measured using camera-based methods, several portable systems using cords connecting directly to the bar are now available. Because many weight training exercises involve the bar moving in multiple planes, which may change across load intensity, the validity of using a linear position transducer (LPT) is of significance. PURPOSE: To compare camera and LPT measurement of vertical bar velocity during front squats and snatches. METHODS: Healthy men (n=7) aged 18 to 35yrs completed one test session during which two repetitions of the front squat and snatch at 50%, 60% and 80% of their reported one repetition maximum (1RM) were completed. Order of exercises performed was randomized. Simultaneous measurement of bar displacement was made by a 12 camera system (Vicon, Oxford, UK) and a LPT (Tendo Power Analyzing Unit, Tendo Power Machines, Slovak Republic), from which peak velocities were computed. Correlational and 95% limits of agreement (LOA) analyses were conducted between the two methods. RESULTS: Strong relationships were revealed between the methods for both the front squat (50%: r=.96, 60%: r=.90, 80%: r=.97) and snatch (50%: r=.92, 60%: r=.99, 80%: r=.99). Camera estimated peak velocities were significantly greater for front squat at 50% (P=.018) and 60% (P=.031) and snatch at 60% (P=.004) and 80% (P=.003). Bias and 95% LOA during the front squat were: .09±.18m/s (50%), .09±.17m/s (60%), and .04±.14m/s (80%). Bias and 95% LOA during the snatch were .10±.52m/s (50%), .28±.32m/s (60%), and .26 ± .28m/s (80%). CONCLUSION: Stronger agreement was evident for the front squat compared to the snatch, which may be explained by the complexity of the snatch lift as it involves a degree of curvature during the second pull and catch. This explanation is plausible given research showing bar curvature during the second pull and catch increases as loads increase. However, given the relative agreement between these measurement techniques, this work does suggest a portable system may be efficacious for use in non-laboratory settings. As this study engaged intermediate lifters, future research should examine the agreement between measurement approaches in elite level lifters, particularly as such lifters may be less likely to increase the curvature of bar trajectory during a snatch life.