Lower extremity skeletal muscle function in persons with incomplete spinal cord injury

A. Jayaraman, C. M. Gregory, M. Bowden, J. E. Stevens, P. Shah, A. L. Behrman, K. Vandenborne*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

Study design: A cross-sectional study design. Objectives: To characterize and specifically quantify impairments in muscle function after chronic incomplete spinal cord injury (SCI). Setting: University of Florida, Gainesville, FL, USA. Methods: Voluntary and electrically elicited contractile measurements were performed and voluntary activation deficits were quantitatively determined in the knee extensor and ankle plantar flexor muscle groups in 10 individuals with chronic incomplete SCI (C5-T8, ASIA C or D) and age-, gender-, height- and body weight matched healthy controls. Results: Persons with incomplete-SCI were able to produce only 36 and 24% of the knee extensor torque and 38 and 26% of the plantar flexor torque generated by noninjured controls in the self-reported less-involved and more-involved limbs, respectively (P<0.05). In addition, both indices of explosive or instantaneous muscle strength, torque200 (absolute torque reached at 200ms) and the average rate of torque development (ARTD) were dramatically reduced in the ankle plantar flexor and knee extensor muscle groups in persons with incomplete-SCI. However, the deficit in instantaneous muscle strength was most pronounced in the ankle plantar flexor muscles, with an 11.7-fold difference between the torque200 measured in the self-reported more involved limb and a 5-fold difference in the less-involved limb compared to control muscles. Voluntary activation deficits ranged between 42 and 66% in both muscle groups. Interestingly, electrically elicited contractile properties did not differ between the groups. Conclusion: The resultant impact of incomplete-SCI is that affected muscles not only become weak, but slow to develop voluntary torque. We speculate that the large deficit in torque 200 and ARTD in the ankle plantar flexors muscles of persons with incomplete-SCI may limit locomotor function. The results presented in this study provide a quantitative and sensitive assessment of muscle function upon which future research examining rehabilitation programs aimed at restoring muscle function and promoting functional recovery after incomplete-SCI may be based.

Original languageEnglish (US)
Pages (from-to)680-687
Number of pages8
JournalSpinal Cord
Volume44
Issue number11
DOIs
StatePublished - Nov 29 2006

Keywords

  • Activation deficit
  • Contractile properties
  • Human
  • Incomplete spinal cord injury
  • Muscle strength

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

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