Journal of Orthopaedic & Sports Physical Therapy - Chris L. Zimmermann, PT, MPT

EMG Comparison of Lateral Step-up and Stepping Machine Exercise

Tue, 09 Sep 2008 00:00:00 EST

Thomas M. Cook, Chris L. Zimmermann, Kevin M. Lux, Chad M. Neubrand, Todd D. Nicholson
The availability and use of stairstepping machines in both the rehabilitation and fitness industries have seen a significant increase in the last several years. The primary purpose of this study was to evaluate the electromyographic (EMG) activity levels of the rectus femoris (R), vastus medialis (V), biceps femoris (B), gastrocnemius (G), and semimembranosus/semitendonosus (S) muscles during exercise on a stepping machine and during performance of an 8-in lateral step-up. Eighteen subjects, without prior knee pathology, participated in the study. The root mean square EMG activity was obtained using surface electromyography and normalized to percent of maximum voluntary isometric contraction. Each exercise was broken down into knee flexion and knee extension phases for descriptive purposes. Analysis of variance (p < .05) was used for between exercise comparisons. Mean R and V activity were significantly greater during the lateral step-up exercise. Mean G activity was significantly greater for stepping machine exercise. Both B and S showed no significant mean differences between exercises. The stepping machine, in general, showed decreased activity during the knee extension phase and very little activity during the knee flexion phase when compared to the lateral step-up. The results indicate that exercise on the stepping machine would result in a more conservative rehabilitation approach for strengthening the quadriceps and hamstrings.

J Orthop Sports Phys Ther 1992;16(3):108-113.

Key Words: electromyography, muscle cocontraction, stairstepping

Effects of Stair-Stepping Exercise Direction and Cadence on EMG Activity of Selected Lower Extremity Muscle Groups

Mon, 05 Feb 2007 09:45:00 EST

Chris L. Zimmermann, Thomas M. Cook, Matthew S. Bravard, Michael M. Hansen, Robin T. Honomichl, Shani T. Karns, Margaret A. Lammers, Star A. Steele, Lisa K. Yunker, Raymond M. Zebrowski

Step ergometry has become a popular treatment mode in cardiovascular fitness and knee rehabilitation programs. The following study describes the effects of forward stair stepping at 35 and 95 steps/minute and forward and retrograde stair stepping at 60 steps/minute on the mean electromyographic (EMG) activity of the gluteus maximus, rectus femoris, vastus medialis, semimembranosus/semitendinosus, and gastrocnemius muscles. Thirty-three subjects without prior lower extremity pathology participated in the study. Analysis of variance was used to compare mean EMG activity during the knee extension phase of the different stepping conditions. Significant differences (p<.05) in mean EMGs of gluteus maximus, rectus femoris, vastus medialis, and gastrocnemius were noted across all cadences. The semimembranosus/semitendinosus EMG activity displayed a single significant difference between the cadences of 35 and 95. The comparison between forward and retrograde stepping identified only one significant difference in mean EMG (semimembranosus/semitendinosus). The effects of cadence on EMG activity should be considered when developing conditioning or rehabilitation programs for the lower extremity. Faster cadences result in increased peak activity of shorter duration for the gluteus maximus, quadriceps, and gastrocnemius. There is no apparent difference in EMG activity of the hamstrings due to cadence. Also, noting the minimal activation that occurs, stair-stepping exercise would not be recommended for strengthening of the hamstrings musculature.

J Orthop Sports Phys Ther. 1994;19(3):173-180.

Key Words: weight bearing, electromyography, stair stepping

Active Surveillance for the Control of Cumulative Trauma Disorders: A Working Model in the Newspaper Industry

Mon, 05 Feb 2007 09:45:00 EST

John C. Rosecrance, Thomas M. Cook, Chris L. Zimmermann

Health and risk factor surveillance is a critical aspect of an effective ergonomics process. Physical therapists are becoming increasingly involved in many components of the ergonomics process, including health and risk factor surveillance. The purpose of this study was to develop and implement a multistaged active surveillance program for the management and control of cumulative trauma disorders. The surveillance program was established at 3 newspaper companies consisting of 1,150 employees. This study focused on the first 3 stages of the multistage surveillance model, which incorporates the use of symptom and job factor questionnaires, specific anatomical surveys, and clinical detection tests. The results of the study indicated that 1) musculoskeletal symptoms in the back, neck, and hands accounted for the majority of reported missed work among the newspaper workers; 2) production workers had a higher prevalence of musculoskeletal symptoms than office workers; and 3) the prevalence of probable carpal tunnel syndrome among the newspaper workers was 1.5%.

J Orthop Sports Phys Ther. 1994;19(5):267-276.

Key Words: ergonomics, cumulative trauma disorders, surveillance