Date of Award

4-2002

Degree Name

Master of Arts

Department

Health, Physical Education & Recreation

First Advisor

Dr. Roger Zabik

Second Advisor

Dr. Yuanlong Liu

Third Advisor

Dr. Timothy Michael

Fourth Advisor

Dr. Mary Dawson

Keywords

Electromyography, muscles, knees

Access Setting

Masters Thesis-Open Access

Abstract

This retrospective study analyzed the three muscles involved in knee extension: vastus medialis, rectus femoris, and vastus lateralis. lt was conducted to determine the reliability of normalization procedures when evaluating the EMG response detected from a muscle. During a maximal voluntary isometric contraction {MVIC), the EMG response of the muscle was recorded and the iEMG moment per unit area was determined. The iEMG response ofthe quadriceps muscles during dynamic exercise was normalized using the MVIC. Subjects (N = 44) performed two consecutive MVICs with a 2-min rest between trials at 110°, 90°, 70°, 50°, and 30° of knee flexion, followed by two submaximal dynamic knee extension exercises. Intraclass correlations were then determined across trials and days. This study determined that flexion angles 50°, 70°, and 90° and days 4 and 5 more consistently achieved the highest reliability. Therefore, in order to obtain reliable recordings, the MVIC used for normalization should be measured using at least five trials at the midrange angles for knee flexion. Also, the Pearson product-moment correlation calculated to determine the relationship between the EMG response during the dynamic exercise at a high and low load showed that the normalization procedures did Iittle to improve this relationship and may in fact have diminished it.

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