Title

Electromyographical and biomechanical analysis of the back squat exercise during high and low speeds

Date of Award

2000

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Exercise and Sport Sciences

First Committee Member

Joseph Signorile, Committee Chair

Abstract

This study compared muscle utilization patterns (NrmsEMG) and biomechanical measures during the parallel squat exercise performed under high speed (HS) and low speed (LS) conditions. The muscles evaluated included longissimus dorsi (LD), rectus abdominis (RA), gluteus maximus (GM), rectus femoris (RF), biceps femoris (BF), vastus lateralis (VL), lateral gastrocnemius (LGAS) and tibialis anterior (TA). Segment velocity and acceleration, and joint forces and moments, were measured for the L2-L3 (L3), Hip (AF), Knee (K) and Ankle (A) joints. Eleven male lifters, 18--34, completed 10 repetitions at 70% maximum voluntary contraction under HS and LS conditions. Differences between conditions were evaluated eccentrically and concentrically using 2 x 2 x 2 repeated measures ANOVA's. Concentric velocity and acceleration data were higher during the HS versus LS condition. Forces and moments were also greater during the HS versus LS condition. The experienced lifters in the study maintained speed, acceleration, force and moment values across the HS and LS sets. In most cases the HS condition produced higher NrmsEMG values than the LS. However, the LS condition produced higher NrmsEMG values during the concentric phase of the lift for the LD and the eccentric phase for the RF and VL. In addition, NrmsEMG increased across sets for most muscles showing that fatigue occurred although it was not measurable using the biomechanical data. It is concluded that the HS squat provides a greater training effect for most muscles due to the greater acceleration, forces and moments and corresponding higher NrmsEMG. The HS squat may also carry a greater potential for lower back injury, however, the higher NrmsEMG in the RA during the lift may act to reduce this risk. The LS squat selectively targeted LD during the concentric lift and the RF and VL during the eccentric lift. It is concluded that the HS squat is an indispensable tool for increasing power output. However the LS squat may provide greater stimuli for the quadriceps group due to the prolonged tension involved in this lift. These data point to the use of both the LS and HS squat during specific stages of a well-designed periodization program.

Keywords

Health Sciences, Rehabilitation and Therapy; Health Sciences, Recreation

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9972557