Date of Award

2017

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Master of Science (Sports Science)

School

School of Medical and Health Sciences

First Supervisor

Professor Ken Nosaka

Second Supervisor

Dr Eric Drinkwater

Abstract

Common resistance-training exercises such as back squat, Romanian deadlift (RDL), and hip thrust have been used by strength and conditioning specialists to target the musculature used during hip extension. Little is known about the differences in muscular activity of the hip extensors between these exercises, so it is not known which is the most effective as a hip extensor exercise. The primary purpose of this study was to compare muscle activity of several muscles during the high-bar back squat, RDL and barbell hip thrust, using men with a minimum of 1 year of lower-body resistance-training experience. Surface electromyography (EMG) was used to record muscle activity from the vastus lateralis (VL), vastus medialis (VMO), biceps femoris (BF), semitendinosus (ST) and gluteus maximus (GM) during a submaximal repetition of each exercise at 60 kg and a 1-repetition maximum (1RM). EMG during the exercises was compared to the EMG of each muscle during a maximum voluntary contraction (MVIC), performed on an isokinetic dynamometer. The results showed that hip thrust displayed higher GM activity than the back squat (mean Δ ± 95% confidence interval; 62.7 ± 58.0 mV, effect size = 1.39. P = 0.038), but no significant differences were seen when comparing the hip thrust and RDL (-37.0 ± 75.7 mV; -0.49. P = 0.285). While the hip thrust displayed higher GM activity when compared to the back squat, no significant differences in EMG activity between a 1RM to an MVIC were seen for the GM (-33.4 ± 58.0 mV; -0.35. P = 0.215), BF (16.1 ± 137.9 mV; 0.16. P = 0.791) and ST (- 49.3 ± 71.1 mV; -0.51. P = 0.145), demonstrating high activation of hip extensors. Highest knee extensor activity at 1RM was seen in back squat. VL activity was largely different between RDL and back squat (-247.5 ± 126.8 mV; -1.36. P = 0.002) and hip thrust and back squat (183.6 ± 120.1 mV; 2.27. P = 0.009), with higher VL activity during the back squat than others. Further, VMO displayed large differences in EMG activity when comparing RDL (268.6 ± 224.8 mV; 3.31. P = 0.026) and barbell hip thrust (151.2 ± 128.8 mV; 0.90. P = 0.027) to back squat, with back squat displaying higher VMO activity at 1RM. These findings highlight the benefits of the back squat when training for athletic movements involving hip and knee extension, as the squat showed the highest knee extensor activation and high hip extensor activity relative to an MVIC. Therefore, while hip thrust may be a valuable movement for those wishing to isolate the hip extensors for rehabilitation or bodybuilding purposes, the back squat still likely has greater application as a functional movement pattern that translates better to the sport setting.

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