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A BIOMECHANICAL COMPARISON OF THE BACK SQUAT AND HEXAGONAL BARBELL DEADLIFT

Abstract

Cody A. Stahl1, Eoghan M.P. Trihy2, David Diggin2, Deborah L. King2 1School of Kinesiology Applied Health and Recreation, Oklahoma State University, Stillwater, Oklahoma; 2Department of Exercise and Sport Sciences, Biomechanics Laboratory, Ithaca College, Ithaca, New York.

Exercises such as the back squat (BS) and conventional deadlift (CDL) are used interchangeably by strength and conditioning coaches to improve athletes’ lower body strength. More recently, the hexagonal barbell deadlift (HBD) has been used as an auxiliary exercise for the CDL and BS. Anecdotally, the HBD encourages amore upright trunk position which can reduce compressive and shear loads on the spine relative to the CDL and BS. PURPOSE: This study examined differences in kinematics and kinetics between BS and HBD exercises during 1RM testing. METHODS: 16 participants volunteered for the study (6 males, 10 females; age 21.4 ± 3.0 years; height 169.7 ± 6.5 cm; mass 73.8 ± 10.9 kg). Participants attended the lab on 2 occasions spaced 7 days apart. Participants underwent 1RM testing of either the BS or HBD during each session. Following a warm-up, participants attempted to achieve their 1RM within 3–5 attempts. Kinematic and kinetic data were collected using a motion capture system and two force plates respectively. RESULTS: Paired-samples t-test results showed participants 1RM under HBD conditions (142.5 ± 47.2 kg) was greater than under BS conditions (108.0 ± 37.3 kg; t(15) = −7.30p< 0.05). Data also showed that participants adopted greater trunk lean under max load in the bottom position of the HBD (69.5±6.9°) compared to that of the BS (48.6± 7.3°; θ trunk; t(15)= 9.76; p< .01). Participants also exhibited a more extended knee position in the bottom position of the HBD (93.1± 11.4°) relative to the BS (119.5± 8.4°; t(15)= 6.42; p< .01). In addition, participants exhibited greater M hip under BS (-227.4± 69.4Nm) relative to HBD conditions (-136.7± 75.1 Nm; t(15)= -6.55; p< .001). Examination of knee joint moments revealed no difference in M knee between exercises (t(15)= -1.67; p= .116). CONCLUSION: At maximum loads, these exercises are not the same based on the mechanical differences experienced. These results suggest that at maximal loads (100% 1-RM) that strength coaches may not want to use these exercises interchangeably.

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