Authors: M Godard P Gallagher U Raue S Trappe
Publish Date: 2014/04/27
Volume: 444, Issue: 3, Pages: 419-425
Abstract
The purpose of this investigation was to determine the effects of a 12week progressive resistancetraining program PRT on single muscle fiber calcium sensitivity in six older women 73±2 years Muscle biopsy samples of the vastus lateralis were obtained pre and postPRT Chemically skinned single muscle fibers n=274 were dissected and studied The experimental sequence for each fiber was the determination of peak maximal isometric tension P o at pCa 45 pCa=–logCa2+ and then subsequent submaximal activations of the fiber at nine Ca2+ concentrations pCa 68 to 47 Myosin heavy chain MHC I fiber slowtwitch diameter increased 16 P005 with no change in MHC IIa fibers fasttwitch pre to postPRT respectively P o in MHC I fibers increased 34 P005 as a result of the training with no change in MHC IIa fibers The mean MHC I Ca2+ activation threshold minimal amount of Ca2+ necessary to induce tension increased from 683±002 to 691±001 P005 as did the mean halfmaximal activation pCa50 551±002 to 571±003 P005 with PRT The slope of the Hill plot above n 1 the pCa50 for MHC I did not change significantly with the PRT However the slope of the Hill plot below n 2 the pCa50 for MHC I demonstrated an increase P005 with training There were no differences with MHC IIa fibers with PRT for any of the variables measured In conclusion the results of this investigation indicate that myofibril Ca2+ sensitivity and activation properties are altered in MHC I but not MHC IIa fibers with PRT in older women The alterations in the MHC I Ca2+ properties appear to have an effect on the mechanisms involved with skeletal muscle adaptability in older women following PRT
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