andrew c. fry

Internal consistency can be defined as the reliability across similar items in a test. Considering the importance of power and velocity during resistance training, it is crucial to have accurate testing methods for quantifying these variables. With recent technological advancements, various devices are increasingly used to quantify barbell velocity and power in the weight room to better understand the exercises prescribed. The purpose of the study was to determine the internal consistency of a novel 3-D camera system and a commonly used tether-based dynamometer by comparing them to a laboratory-based linear position transducer. To assure a consistent stimulus, one weight-trained male (age = 28 yrs, height = 1.78 m, mass = 97.1 kg, 1RM squat = 226.8 kg) completed 10 sets of 1 repetition with maximal concentric acceleration at each prescribed load of 30, 40, 50, 60, 70, and 80% of his individual 1RM, for a total of 60 repetition trials. All devices used in this study collected the data simultaneously. All three methods of measurement exhibited strong correlations (r ≥ 0.80) while Cronbach alpha values for mean velocity, peak velocity, mean power, and peak power were 0.998, 0.995, 0.981, 0.951, respectively. Bland-Altman plots showed that all four variables were well within 95% limits of agreement. Based on our results, we can conclude that the use of a 3-D camera system or a tether-based external dynamometer provides measures of barbell velocities and powers consistent with laboratory-derived measures. These findings indicate strength and conditioning professionals can monitor resistance training with any of the systems used and achieve similarly consistent values.