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Advanced sarcopenia is prevalent among octogenarian women; yet little is known about myocellular quality and plasticity in this cohort. The aim of this investigation was to examine single muscle fiber contractile function and whole muscle characteristics before and after 12 wk of high-intensity progressive resistance training (PRT) in very old (85 Â± 1 yr) women (OW, n = 6). Young women [YW (21 Â± 2 yr old), n = 9] were included as a control group. Whole muscle strength [1 repetition maximum (RM)] and size (CT scans) were assessed before and after PRT. Functional experiments (size, peak force, velocity, and power) were performed on vastus lateralis myosin heavy chain (MHC) I and IIa muscle fibers before and after PRT. With PRT, 1-RM strength increased (P < 0.05) in YW (36%) and OW (26%). Thigh muscle cross-sectional area increased (5%) in YW (P < 0.05), but thigh muscle did not hypertrophy in OW. Before PRT, there were no differences in single-fiber parameters between YW and OW. With PRT, MHC IIa fiber size (28%), peak force (31%), and power (28%) improved, but no changes were observed in MHC I fibers, in YW (P < 0.05). There were no improvements in MHC I or IIa single-fiber function in OW. These data show that the myocellular functional profile in OW is similar to that in YW but that OW have a blunted hypertrophic response to PRT at the whole muscle and myocellular level. The limited myocellular plasticity in OW with PRT contrasts with that in YW and previous PRT studies in elderly women only a decade younger. These data suggest that attempts to greatly enhance skeletal muscle mass and function should begin before 80 yr of age.
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