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Article

Functional Roles of the Leg Muscles When Pedaling in the Recumbent Versus the Upright Position

[+] Author and Article Information
Nils A. Hakansson

Department of Mechanical Engineering,  Biomedical Engineering Program, University of California, Davis, CA 95616

M. L. Hull1

Department of Mechanical Engineering,  Biomedical Engineering Program, University of California, Davis, CA 95616mlhull@ucdavis.edu

1

Corresponding author.

J Biomech Eng 127(2), 301-310 (Sep 10, 2004) (10 pages) doi:10.1115/1.1865192 History: Received September 25, 2003; Revised September 10, 2004

An understanding of the coordination of the leg muscles in recumbent pedaling would be useful to the design of rehabilitative pedaling exercises. The objectives of this work were to (i) determine whether patterns of muscle activity while pedaling in the recumbent and upright positions are similar when the different orientation in the gravity field is considered, (ii) compare the functional roles of the leg muscles while pedaling in the recumbent position to the upright position to the upright position and (iii) determine whether leg muscle onset and offset timing for recumbent and upright pedaling respond similarly to changes in pedaling rate. To fulfill these objectives, surface electromyograms were recorded from 10 muscles of 15 subjects who pedaled in both the recumbent and upright positions at 75, 90, and 105rpm and at a constant workrate of 250W. Patterns of muscle activation were compared over the crank cycle. Functional roles of muscles in recumbent and upright pedaling were compared using the percent of integrated activation in crank cycle regions determined previously for upright pedaling. Muscle onset and offset timing were also compared. When the crank cycle was adjusted for orientation in the gravity field, the activation patterns for the two positions were similar. Functional roles of the muscles in the two positions were similar as well. In recumbent pedaling, the uniarticular hip and knee extensors functioned primarily to produce power during the extension region of the crank cycle, whereas the biarticular muscles crossing the hip and knee functioned to propel the leg through the transition regions of the crank cycle. The adaptations of the muscles to changes in pedaling rate were also similar for the two body positions with the uniarticular power producing muscles of the hip and knee advancing their activity to earlier in the crank cycle as the pedaling rate increased. This information on the functional roles of the leg muscles provides a basis by which to form functional groups, such as power-producing muscles and transition muscles, to aid in the development of rehabilitative pedaling exercises and recumbent pedaling simulations to further our understanding of task-dependent muscle coordination.

FIGURES IN THIS ARTICLE
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Copyright © 2005 by American Society of Mechanical Engineers
Topics: Muscle , Cycles
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Figures

Grahic Jump Location
Figure 1

The phase-controlled functional regions for the recumbent position (gray) and the upright position (black). The four primary regions for the upright position are based on the work of Raasch (7) and include the extension (E), distal transition (D), flexion (F), and proximal transition (P) regions. The corresponding regions for the recumbent position have been rotated by 54deg in the counterclockwise direction to account for the different seat angle with respect to the upright position.

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