Muscle after spinal cord injury.
The morphological and contractile changes of muscles below the level of the lesion after spinal cord injury (SCI) are dramatic. In humans with SCI, a fiber-type transformation away from type I begins 4-7 months post-SCI and reaches a new steady state with predominantly fast glycolytic IIX fibers years after the injury. There is a progressive drop in the proportion of slow myosin heavy chain (MHC) isoform fibers and a rise in the proportion of fibers that coexpress both the fast and slow MHC isoforms. The oxidative enzymatic activity starts to decline after the first few months post-SCI. Muscles from individuals with chronic SCI show less resistance to fatigue, and the speed-related contractile properties change, becoming faster. These findings are also present in animals. Future studies should longitudinally examine changes in muscles from early SCI until steady state is reached in order to determine optimal training protocols for maintaining skeletal muscle after paralysis.
Biering-Sørensen
Bo
B
Clinic for Spinal Cord Injuries, NeuroScience Centre, Rigshospitalet, Copenhagen University Hospital, Havnevej 25, DK-3100 Hornbaek, Denmark. bobiering@hotmail.com
Kristensen
Ida Bruun
IB
Kjaer
Michael
M
Biering-Sørensen
Fin
F
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002415:Cats; D004195:Disease Models, Animal; D005260:Female; D006019:Glycolysis / Q000502:physiology; D006801:Humans; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism / Q000473:pathology*; D010084:Oxidation-Reduction; D011817:Rabbits; D051381:Rats; D012039:Regional Blood Flow / Q000502:physiology; D013119:Spinal Cord Injuries / Q000378:metabolism / Q000473:pathology*
D000251:Adenosine Triphosphatases