A Biomechanical Comparison of the Back Squat and Hexagonal Barbell Deadlift.

ABSTRACT: Stahl, CA, Regni, G, Tanguay, J, McElfresh, M, Trihy, E, Diggin, D, and King, DL. A biomechanical comparison of the back squat and hexagonal barbell deadlift. J Strength Cond Res 38(5): 815-824, 2024-Coaches often use different exercises to encourage similar strength adaptations and limit monotony. Anecdotally, the hexagonal barbell deadlift (HBD) exhibits similarities to the back squat (BS). To date, research has not examined the empirical differences between these exercises. This study examined kinematic and kinetic differences between the BS and the HBD across different loads. Sixteen resistance-trained individuals (6 men and 10 women) volunteered to participate. Subjects performed 1-repetition maximum (1RM) testing under BS and HBD conditions. Kinematic and kinetic data were collected during performance of both exercises at submaximal (warm-up sets) and maximal (1RM) loads using a 3D motion capture and force-plate system. Results showed that subjects lifted greater 1RM loads in the HBD relative to the BS (p < 0.05; d = -1.75). Kinematic data indicated that subjects exhibited greater maximum forward lean of the trunk and decreased maximum knee flexion while performing the HBD compared with the BS. The BS resulted in higher maximum extension moments at the hip joint than the HBD. Maximum extension moments at the knee joint showed no difference between the exercises. Data suggest that bar design and position facilitate balanced moment arm length at hip and knee joints during performance of the HBD. By contrast, bar position during performance of the BS increases moment arm length at the hip joint, making it a hip-dominant exercise. The present data have implications for the programming of both exercises. Future research should examine differences in muscle-activation strategies between the 2 exercises.

Initial contact and toe off event identification for rearfoot and non-rearfoot strike pattern treadmill running at different speeds.

The purpose of this study was to determine the validity of kinematic based initial contact (IC) and toe-off (TO) identification algorithms for rearfoot and non-rearfoot runners across a broad range of treadmill running speeds. 14 healthy active participants completed six 20-60 s treadmill running trials at 6 speeds: 2.24, 2.68, 3.13, 3.58, 4.02, and 4.48 ms-1. 3D kinematic data were collected for the last 20 s of each trial. Force plates (FP) were used as the gold standard to determine ICFP and TOFP for each step. Three algorithms for finding IC, ICMilner, ICAlvim, ICAlvim-mod, and one algorithm for finding toe off, TOFellin, were chosen for analysis. Root mean square errors (RMSE) and difference scores with 95% confidence intervals were computed for IC, TO and stance time (ST). ICAlvim RMSE ranged from 0.175 to 0.219 s. STAlvim RMSE ranged from 0.168 to 0.216 s. ICAlvim-mod RMSE ranged from 0.105 to 0.131 s. STAlvim-mod RMSE ranged from 0.108 to 0.129 s. ICMilner RMSE ranged 0.012 to 0.015 s. STMilner RMSE ranged 0.019 to 0.024 s. ICMilner accuracy was inversely related to speed. ICMilner corrected with a linear regression equation reduced differences to- 0.006 ±â€¯0.012 s with 86% of foot strikes identified within 20 ms and 58% with 10 ms. TOFellin RMSE ranged from 0.012 to 0.016 s. ICMilner adjusted for speed and TOFellin can be used to predict IC and TO within a broad range of treadmill running speeds (2.24-4.48 ms-1) and for rearfoot and non-rearfoot strikers.