Date of Award

Spring 8-1-2005

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Athletic Training

First Advisor

Mitchell L. Cordova

Second Advisor

John R. Storsved II

Abstract

Objective: Clinicians often use Swiss balls in exercise regimens to recruit activity of the paraspinal musculature. However, we do not know if muscle activity differences exist while performing an exercise on a stable or unstable surface. Design and Settings: A 1 X 2 factorial with repeated measures design guided this study. The single within-subjects factor was a core stability exercise with 2 levels: a stable condition (chair) and an unstable condition (Thera-band® exercise ball). The dependent variables were the integrated electromyography (I-EMG) amplitude of the left and right lumbar paraspinal musculature. Subjects: Sixteen moderately active and healthy male subjects (age: 24.3 ± 2.2 yrs, ht: 180.3 ± 6.9 em, mass: 77.8 ± 11.0 kg, left skinfold thickness:9.2 ± 4.1 mm, right skinfold thickness: 9.4 ± 3.8 mm) without any indication of low back pain within the last 6 months, participated. Measurements: I-EMG recordings were taken from the left lumbar paraspinal muscles (LLPM) and right lumbar paraspinal muscles (RLPM), while performing a core stability exercise on a stable and unstable condition. Two pairs of self-adhesive silver-silver chloride surface electrodes were arranged bilaterally 3 em lateral to the L3 spinous process. A 6 s maximum voluntary isometric contraction (MVIC) of a resisted trunk extension was recorded prior to the first exercise condition. Five trials of each exercise condition were recorded for 20 s, averaged and normalized to the activity of the MVIC. Results: According to the I-EMG of the LLPM, core stability exercises when performed on a stable (33.6% ± 11.2) or unstable (38.01% ± 13.9) IV condition caused similar levels of activation (t15 = -1.42, P = 0.18). On the other hand, activity of the RLPM was greater during the unstable (44.6% ± 23.5) condition than the stable (36.4% ± 16.2) condition (tt5 = -2.38, P = 0.03). Conclusions: It is apparent that performing an exercise on an unstable condition will recruit more activity in the RLPM as compared with the exercise performed on the stable surface. The result of the LLPM showing no difference between the two exercises may be attributed to the lack of dominance, strength or endurance of the LLPM of the subject pool. The results found for the RLPM can help clinicians establish higher quality lumbar paraspinal exercise regimens, using an unstable surface.

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