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TECHNICAL PAPERS: Joint/Whole Body

# How Changing the Inversion/Eversion Foot Angle Affects the Nondriving Intersegmental Knee Moments and the Relative Activation of the Vastii Muscles in Cycling

[+] Author and Article Information
Colin S. Gregersen, Nils A. Hakansson

Biomedical Engineering Program, One Shields Avenue, University of California, Davis, CA 95616

M. L. Hull

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

J Biomech Eng 128(3), 391-398 (Dec 19, 2005) (8 pages) doi:10.1115/1.2193543 History: Received March 12, 2004; Revised December 19, 2005

## Abstract

Nondriving intersegmental knee moment components (i.e., varus/valgus and internal/external axial moments) are thought to be primarily responsible for the etiology of overuse knee injuries such as patellofermoral pain syndrome in cycling because of their relationship to muscular imbalances. However the relationship between these moments and muscle activity has not been studied. Thus the four primary objectives of this study were to test whether manipulating the inversion/eversion foot angle alters the varus/valgus knee moment (Objective 1) and axial knee moment (Objective 2) and to determine whether activation patterns of the vastus medialis oblique (VMO), vastus lateralis (VL), and tensor fascia latae (TFL) were affected by changes in the varus/valgus (Objective 3) and axial knee moments (Objective 4). To fulfill these objectives, pedal loads and lower limb kinematic data were collected from 15 subjects who pedaled with five randomly assigned inversion/eversion angles: 10 deg and 5 deg everted and inverted and $0deg$ (neutral). A previously described mathematical model was used to compute the nondriving intersegmental knee moments throughout the crank cycle. The excitations of the VMO, VL, and TFL muscles were measured with surface electromyography and the muscle activations were computed. On average, the 10-deg everted position decreased the peak varus moment by 55% and decreased the peak internal axial moment by 53% during the power stroke (crank cycle region where the knee moment is extensor). A correlation analysis revealed that the VMO/VL activation ratio increased significantly and the TFL activation decreased significantly as the varus moment decreased. For both the VMO/VL activation ratio and the TFL activation, a path analysis indicated that the varus/valgus moment was highly correlated to the axial moment but that the correlation between muscle activation and the varus moment was due primarily to the varus/valgus knee moment rather than the axial knee moment. The conclusion from these results is that everting the foot may be beneficial towards either preventing or ameliorating patellofemoral pain syndrome in cycling.

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Topics: Muscle , Knee , Stress

## Figures

Figure 1

(a) Diagram illustrating pedal dynamometer reflective markers and local pedal coordinate system. (b) Diagram illustrating lower limb reflective markers and virtual joint centers for the ankle and knee joints. The knee joint center served as the origin of the local shank coordinate system in which the knee load components were computed.

Figure 2

Photograph of six-load-component pedal dynamometer with inversion/eversion interface attached. The interface also has a medial/lateral translational adjustment.

Figure 3

Sample nondriving knee moments for one subject (subject 10) at the neutral (0), 10 degrees inverted (+10), and 10deg everted (−10) foot angles. The varus (+Mx′)/valgus (−Mx′) and internal (+Mz′)/external (−Mz′) axial moments are expressed as net moments applied to the tibia.

Figure 4

Contributions of individual pedal loads to the varus/valgus (Mx′) and internal/external axial (Mz′) knee moments for subject 10. Contributions are grouped by the inversion/eversion treatments, neutral (“0”) and 10-deg everted (“−10”). Only the major contributors to each load component are plotted.

Figure 5

Path analysis results of the relative contributions by each of the nondriving knee moments to the correlation values in Table 3 for the VMO/VL ratio. (a) average VMO/VL ratio to varus and internal axial peaks, and (b) average VMO/VL ratio to varus/valgus and internal/external axial averages. The weights of the lines indicate the relative strength of the correlation (r values) between quantities presented. The r value between moment quantities is the correlation coefficient ρ(x1,x2) and the r values between moment quantities and muscle quantities are the standardized regression coefficients b1 and b2. The r values between moment quantities were highly significant (p<0.0001). See text for further explanation.

Figure 6

Path analysis results of the relative contributions by the nondriving knee moments to the correlation values in Table 3 for the TFL activity. (a) TFL average to varus and internal axial peaks, and (b) TFL average to varus/valgus and internal/external axial averages. The weights of the lines represent the relative strength of the correlation (r values) between quantities presented. The r value between moment quantities is the correlation coefficient ρ(x1,x2) and the r values between moment quantities and muscle quantities are the standardized regression coefficients b1 and b2. The r values between moment quantities were highly significant (p<0.0001). See text for further explanation.

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