| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Institut d' education physique et de readaptation, Universite catholique de Louvain, Louvain-la-Neuve, Belgium
2 Institut d'education physique et de readaptation, Universite catholique de Louvain, Louvain-la-Neuve, Belgium
* To whom correspondence should be addressed. E-mail: daniel.theisen{at}uclouvain.be.
This study compared human muscles following long-term reduced neuromuscular activity to those with normal functioning regarding single fiber properties. Biopsies were obtained from the vastus lateralis of 5 individuals with chronic (>3 years) spinal cord injury (SCI) and 10 able-bodied controls (CTRL). Chemically skinned fibers were tested for active and passive mechanical characteristics and subsequently classified according to myosin heavy chain (MHC) content. SCI individuals had smaller proportions of type I (11±7 vs. 34±5%) and IIa fibers (11±6 vs. 31±5%), while type IIx fibers were more frequent (40±13 vs. 7±3%) compared to CTRL subjects (P<0.05). Cross-sectional area and peak force were similar in both groups for all fiber types. Unloaded shortening velocity of fibers from paralyzed muscles was higher in type IIa, IIa/IIx and IIx fibers (26%, 65% and 47%, respectively, P<0.01). Consequently, absolute peak power was greater in type IIa (46%, P<0.05) and IIa/IIx fibers (118%, P<0.01) of the SCI group, while normalized peak power was higher in type IIa/IIx fibers (71%, P<0.001). Ca2+ sensitivity and passive fiber characteristics were not different between the two groups in any fiber type. Composite values (average value across all fibers analyzed within each study participant) showed similar results for cross-sectional area and peak force, while maximal contraction velocity and fiber power were more than 100% greater in SCI individuals. These data illustrate that contractile performance is preserved or even higher in the remaining fibers of human muscles following reduced neuromuscular activity.
This article has been cited by other articles:
|
|
 |
|
  C. K. Thomas, C. K. Hager-Ross, and C. S. Klein Effects of baclofen on motor units paralysed by chronic cervical spinal cord injury Brain, November 10, 2009; (2009) awp285v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 O. Agbulut, A. Vignaud, C. Hourde, E. Mouisel, F. Fougerousse, G. S. Butler-Browne, and A. Ferry Slow myosin heavy chain expression in the absence of muscle activity Am J Physiol Cell Physiol, January 1, 2009; 296(1): C205 - C214. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Harber and S. Trappe Single muscle fiber contractile properties of young competitive distance runners J Appl Physiol, August 1, 2008; 105(2): 629 - 636. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. R. Frontera, K. F. Reid, E. M. Phillips, L. S. Krivickas, V. A. Hughes, R. Roubenoff, and R. A. Fielding Muscle fiber size and function in elderly humans: a longitudinal study J Appl Physiol, August 1, 2008; 105(2): 637 - 642. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Slivka, U. Raue, C. Hollon, K. Minchev, and S. Trappe Single muscle fiber adaptations to resistance training in old (>80 yr) men: evidence for limited skeletal muscle plasticity Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2008; 295(1): R273 - R280. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. C. Dreyer, E. L. Glynn, H. L. Lujan, C. S. Fry, S. E. DiCarlo, and B. B. Rasmussen Chronic paraplegia-induced muscle atrophy downregulates the mTOR/S6K1 signaling pathway J Appl Physiol, January 1, 2008; 104(1): 27 - 33. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Trappe, A. Creer, D. Slivka, K. Minchev, and T. Trappe Single muscle fiber function with concurrent exercise or nutrition countermeasures during 60 days of bed rest in women J Appl Physiol, October 1, 2007; 103(4): 1242 - 1250. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
