Objectives: To compare knee flexors and extensors muscle strength, total work, and power between females with fibromyalgia (FM) and matched healthy controls.

Methods: This is the first study to measure knee muscle power and total work in females with FM. Thirty-one females with FM and thirty-one healthy females completed isokinetic testing of knee flexors and extensors of their dominant leg using a Cybex Norm Isokinetic Dynamometer. Two knee muscle groups (flexors and extensors) at two angular velocities (607sec and 1807sec) were tested for both groups. Both muscle groups were assessed continuously using five reciprocal concentric-concentric cycles, followed by five eccentric-eccentric cycles.

Results:Females with FM exhibited significant decreases in voluntary muscle strength ranging from 18%-24% and average power ranging from 25%-30%, more pronounced for knee flexors than knee extensors. The strength and power deficits were not uniform during all test arrangements: 1) Maximum eccentric muscle strength for knee flexors and extensors at an angular velocity of 60 /sec in females with FM was reduced compared to the control group (p = .005 and .007, respectively), 2) Maximum concentric muscle strength for knee flexors at an angular velocity of 180 /sec in females with FM was reduced compared to the control group (p = .002), and 3) Average power for knee flexors at an angular velocity of 607sec for eccentric muscle action and 1807sec for concentric muscle action in females with FM was reduced compared to the control group (p =.006 and .001, respectively). No differences in total work at the two different velocities for the two muscle actions were found.

Conclusion: We found decreased knee muscle strength and power in females with FM compared to healthy females. This may be due to muscle soreness from unhealed microtraumas, slow deformation of collagen and periarticular connective tissue of the knee joint, hypoxia, or decreased content of high energy metabolites.

LLU Discipline

Physical Therapy


Physical Therapy Sciences


School of Allied Health Professions

First Advisor

Grenith J. Zimmerman

Second Advisor

Keith K. Colburn

Third Advisor

Everett B. Lohman III

Fourth Advisor

Bradford D. Martin

Fifth Advisor

James M. Syms

Degree Name

Doctor of Physical Therapy (DPT)

Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Fibromyalgia. Knee; Muscle Strength -- physiology; Female -- physiology.



Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives