Hamstring and Quadriceps Motor Unit Activation during Resistance Training and Plyometric Exercise
Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
The purpose of this study was to investigate electromyographical (EMG) activation of the hamstring (H) and quadriceps (Q) muscle groups, and their ratio of activation during the performance of resistance training (RT) and plyometric (P) exercises. These variables have not previously been investigated despite the belief that quantifying RT and P exercises is important for program design. Furthermore, gender differences in H and Q activation and H:Q ratio have been proposed and linked to H and anterior cruciate ligament (ACL) injury, though no previous work has evaluated these variables during RT and P, despite the fact that these two training modes are considered to be critical for performance enhancement and injury prevention. Sixty-seven subjects volunteered to participate in two phases of this study designed to investigate these research questions. Thirty four subjects volunteered as subjects for the first part of the study designed to assess H, Q, and H to Q activation ratio during a variety of lower body RT exercises thought to be effective at recruiting the H muscle group, including the squat, Russian curl, seated leg curl, stiff leg dead lift, single leg stiff leg dead lift and good morning exercise. During the second phase of this study, twenty-three subjects volunteered to participate in order to evaluate motor unit activation of the H and Q during the performance of ten P exercises. Data were collected during 10 randomly ordered exercises including 2 foot ankle hops, 15 cm cone hops, tuck, box, and pike jumps, 1 and 2 leg vertical jump and reach, squat jumps with approximately 30 percent of 1RM load, and 30 and 61cm depth jumps. Female subjects demonstrate a trend toward less concentric Q activation during P exercises that have the greatest overload, such as during P exercises with added mass, performed on only one leg, and for drop jumps of greater height, compared to P with less overload...