Date of Degree

5-2015

Document Type

Capstone Project

Degree Name

D.P.T.

Program

Physical Therapy

Advisor(s)

Suzanne Babyar

Subject Categories

Physical Therapy

Abstract

PURPOSE: A common clinical concern of Physical Therapists is the inexplicably weak gluteus maximus (GM) muscle; we hypothesized that this may be linked to the popular habit of prolonged sitting. The purpose of this study was to determine if surface electromyography (sEMG) output and timing of the GM and hamstrings muscles differed between people who sit for prolonged periods of time and people who stand for prolonged periods of time. METHODS: The design of our study was a single session case-control study. Subjects were 22 healthy adults (23-36 years old) who either sat or stood for 8-10 hours a day at least 5 days per week. There were 11 subjects in each group. Written informed consent and questionnaires were obtained at the start of the session, with all forms and procedures approved by the CUNY Human Research Protection Program. The BioNomadix MP150 EMG system collected sEMG during: a manual muscle test (Maximum Voluntary Isometric Contraction) of both the GM and hamstrings muscles; the functional activity of sit-to-stand; and, during a repeated forward step-up. The maximum sEMG signal amplitude recorded during the Maximum Voluntary Isometric Contraction (MVIC) of each muscle represents 100% muscle activity, and the sEMG activity recorded during the functional activities was expressed as a percentage of the MVIC. Relative timing of muscle onset was recorded. DATA ANALYSIS: Repeated measures Multivariate Analysis of Variance (MANOVA) was used to compare normalized mean signal amplitude levels, expressed as a percent of a MVIC, across functional tasks. Friedman tests were used to analyze muscle onset. Post hoc testing with pairwise comparisons were used to find further significance. Bonferonni correction was applied to eliminate false positives. RESULTS: Repeated measures MANOVA did not reveal any main effects or interactions for muscle activity. Friedman tests showed similar results with timing data. Post hoc tests failed to meet the criteria of the Bonferroni correction. The data showed the similarity of muscle timing and activation specifically during the sit-to-stand task in both the sitting group and standing group. CONCLUSIONS: When comparing the sEMG muscle activity of the GM and hamstring muscles during sit-to-stand and a repeated forward-step up in subjects that sit for 8 hours or more per weekday to those who stand for 8 hours or more, no statistical significance differences were found. However, this could be due to limitations of the study such as small sample size, a sample that did not accurately represent the general public, and absence of kinematic data. Due to these limitations further research in this area is needed to determine whether or not prolonged sitting can be linked to decreased sEMG output and timing of the GM.

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