Training by low-frequency stimulation of tibialis anterior in spinal cord-injured men.
The tibialis anterior muscle of nine paraplegic men was chronically stimulated (2-6 h per day; at 10 Hz, 5 s on, 5 s off) under isometric loading conditions for 5 days per week for 4 weeks. After 4 weeks of training, muscle fatigue resistance in an electrically evoked test had increased by an average of 75% (P <.01, n = 9), but there were no changes in the relative composition of the three myosin heavy chain (MHC) isoforms. Five of the subjects continued training for an additional 5 weeks (2 h per day, 3 days per week). Although there was a tendency for twitch time to peak torque to increase after this additional period, no change occurred in relative MHC isoform content. However, in situ hybridization analysis revealed that even after 2 weeks of stimulation, there was evidence of upregulation of the mRNA for the MHC-I isoform and downregulation of the MHC-IIX isoform, a development that continued in weeks 4 and 9. This study provides evidence, at the level of gene transcription, that a fast-to-slow change in MHC isoform composition may be possible in human muscle when its usage is significantly increased.
Harridge
Stephen D R
SDR
Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark.|Department of Physiology, Royal Free and University College Medical School, Rowland Hill Street, London NW3 2PF, United Kingdom.
Andersen
Jesper L
JL
Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark.
Hartkopp
Andreas
A
Centre for Spinal Cord Injured, Neuroscience Centre, Rigshospitalet, Copenhagen, Denmark.
Zhou
Shu
S
School of Exercise Science and Sport Management, Southern Cross University, Lismore, Australia.
Biering-Sørensen
Fin
F
Centre for Spinal Cord Injured, Neuroscience Centre, Rigshospitalet, Copenhagen, Denmark.
Sandri
Claudia
C
Consiglio Nazionalle delle Ricerche Center of Muscle Biology and Physiopathology, Department of Biomedical Sciences, Padova, Italy.
Kjaer
Michael
M
Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark.|Sports Medicine Research Unit, Bispebjerg Hospital, Copenhagen, Denmark.
D000328:Adult; D015536:Down-Regulation; D004558:Electric Stimulation; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D010264:Paraplegia / Q000503:physiopathology; D010806:Physical Education and Training / Q000379:methods*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013997:Time Factors; D015854:Up-Regulation
D020033:Protein Isoforms; D018995:Myosin Heavy Chains