The Reliability and Validity of Current Technologies for Measuring Barbell Velocity in the Free-Weight Back Squat and Power Clean

Abstract

<jats:p>This study investigated the inter-day and intra-device reliability, and criterion validity of six devices for measuring barbell velocity in the free-weight back squat and power clean. In total, 10 competitive weightlifters completed an initial one repetition maximum (1RM) assessment followed by three load-velocity profiles (40–100% 1RM) in both exercises on four separate occasions. Mean and peak velocity was measured simultaneously on each device and compared to 3D motion capture for all repetitions. Reliability was assessed via coefficient of variation (CV) and typical error (TE). Least products regression (LPR) (R2) and limits of agreement (LOA) assessed the validity of the devices. The Gymaware was the most reliable for both exercises (CV &lt; 10%; TE &lt; 0.11 m·s−1, except 100% 1RM (mean velocity) and 90‒100% 1RM (peak velocity)), with MyLift and PUSH following a similar trend. Poorer reliability was observed for Beast Sensor and Bar Sensei (CV = 5.1–119.9%; TE = 0.08–0.48 m·s−1). The Gymaware was the most valid device, with small systematic bias and no proportional or fixed bias evident across both exercises (R2 &gt; 0.42–0.99 LOA = −0.03–0.03 m·s−1). Comparable validity data was observed for MyLift in the back squat. Both PUSH devices produced some fixed and proportional bias, with Beast Sensor and Bar Sensei being the least valid devices across both exercises (R2 &gt; 0.00–0.96, LOA = −0.36–0.46 m·s−1). Linear position transducers and smartphone applications could be used to obtain velocity-based data, with inertial measurement units demonstrating poorer reliability and validity.</jats:p>

Video-Based System for Automatic Measurement of Barbell Velocity in Back Squat

“…The lower systematic values of these studies with respect to ours could be due to the different type of kinematic variables under test (peak vs. mean velocity). The same app tested for mean velocity gave similar results to the proposed video system (0.01 m/s [ 11 ]). For the study of a smartphone app measuring mean velocity values across a series using timekeeping [ 10 ], the systematic bias is even larger and negative (–0.022 m/s), although all errors are negligible in comparison to typical velocity ranges.…”

“…In the field of VBT, as an efficient force training, the velocity of weight displacement can be regarded as the most important parameter to monitor and prescribe individually tailored training programs [ 4 ]. Velocity can be derived either from instantaneous displacement differentiation using position-tracking instruments, with LPT being the most popular instrument [ 11 , 49 ], or from acceleration integration using inertial measurement units [ 50 ]. The first type of instrument relies on accurate measurement of the dynamic position of the object of interest, namely, the barbell in force training.…”

“…For the study of a smartphone app measuring mean velocity values across a series using timekeeping [ 10 ], the systematic bias is even larger and negative (–0.022 m/s), although all errors are negligible in comparison to typical velocity ranges. Likewise, the random errors given by the narrow limits of agreement observed for all the study variables (range: ± 0.47 cm, velocity: ± 0.018 m/s, force: ± 17.6 N, and power: ± 30.34 W) suggested that the video system shows less error variance than My Lift for peak (± 0.04 m/s [ 17 ], ± 0.28 m/s [ 20 ]) and mean velocity values (±0.05 m/s [ 11 ]), and other apps (± 0.034 m/s [ 47 ]). The Pearson’s product-moment correlation and the regression line of the measured average values and the differences between systems in a Bland–Altman plot can reveal if the systematic error is steady and independent of the sample of measured values [ 1 ].…”

“…The different kinetic and kinematic variables relevant to VBT were calculated, taking into consideration only the time when the barbell was moved by the athlete in the concentric or lifting phase [ 11 ]. The main source of information was the instantaneous position of the barbell through time measured with the tracking capability of the algorithm.…”

“…First, linear position transducers (LPTs), which are composed of a string attached to a barbell and connected to a rotational encoder, have been used for decades as the gold standard because of the direct measurement of linear displacement, high sampling rate capture (around 1000 Hz), and reliability [ 8 , 9 ]. LPTs are expensive equipment with moving rotating parts and delicate strings that need appropriate use and limit the range of motion lifts [ 10 , 11 ]. Alternatively, inertial measurement units (IMUs) are able to record changes in gravitational acceleration in selected body parts (usually forearms) or barbells [ 12 , 13 ].…”