FORCES ON THE LUMBAR SPINE DURING THE PARALLEL SQUAT
AbstractINTRODUCTION The benefits of the parallel squat include enhanced lower body musculature, the development of explosive strength, and an increase in ligament and tendon strength. These benefits tend to overshadow the fact that squatting places excessive stress on the musculoskeletal system (Shirazi-Adl, 1994). The purpose of this study was to determine the compression, torsion, and shear forces on the lumbar spine during the patallel squat for experienced and recreational weight men. llventy male subjects were divided into two groups based on experience with the parallel squat. Each subject was f h e d lifting 5 repetitions of 4 weight loads (45 lbs, 225 lbs, body weight (BW), 1.25xBW). The last repetition for each weight load was digitized. A MANOVA was used to determine differences (a<.05) between the 2 groups across the 4 weight loads. RESULTS AND IMPLICATIONS Forces were significantly more between 45 lbs and the other three loads for both compression and shear forces. The experienced group had significantly less torsion than the recreational group. All other main effects and interactions were not significant (ac.05) (See Table 1 .). Recreational and experienced lifters should not be encouraged to increase the weight lifted until the weight can be lowered at a constant slow speed with a minimum trunk angle of 60 degrees. Recreational lifters need to be aware of continued hip flexion after reaching maximal knee flexion. To reduce injuries, proper form should be stressed over increased weight loads. REFERENCES Chaffin, D., Page, G. (1994). Postural effects on biomechanical and psychophysical weight lifting limits. Ergonomics. 37(4), 663-676. McLaughlin, T., Lardner, T., Dillman, C. (1978). Kinetics of the parallel squat. Research Quarterly for Exercise and Sport. 49(2), 175- 189. Shirazi-Adl, A. (1994). Biomechanics of the lumbar spine in sagittal and lateral movements. Spine.
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