Myosin content of single muscle fibers following short-term disuse and active recovery in young and old healthy men

TY - JOUR

T1 - Myosin content of single muscle fibers following short-term disuse and active recovery in young and old healthy men

AU - Hvid, Lars G

AU - Brocca, Lorenza

AU - Ørtenblad, Niels

AU - Suetta, Charlotte

AU - Aagaard, Per

AU - Kjaer, Michael

AU - Bottinelli, Roberto

AU - Pellegrino, Maria Antonietta

N1 - Copyright © 2016 Elsevier Inc. All rights reserved.

PY - 2017/1/1

Y1 - 2017/1/1

N2 - Short-term disuse and subsequent recovery affect whole muscle and single myofiber contractile function in young and old. While the loss and recovery of single myofiber specific force (SF) following disuse and rehabilitation has been shown to correlate with alterations in myosin concentrations in young, it is unknown whether similar relationships exist in old. Therefore, the purpose of the present study was to examine the effect of 14days lower limb disuse followed by 28days of active recovery on single muscle fiber myosin content in old (68yrs) and young (24yrs) recreationally physically active healthy men. Following disuse, myosin content decreased (p<0.05) in MHC 1 (young -28%, old -19%) and 2a fibers (young -23%, old -32%). In old, myosin content decreased more (p<0.05) in MHC 2a vs 1 fibers. Following recovery, myosin content increased (p<0.05) and returned to pre-disuse levels for both young and old in both fiber types, with MHC 2a fibers demonstrating an overshooting in young (+31%, p<0.05) but not old. Strong correlations were observed between myosin content and single fiber SF in both young and old, with greater slope steepness in MHC 2a vs 1 fibers indicating an enhanced intrinsic contractile capacity of MHC 2a fibers. In conclusion, adaptive changes in myofiber myosin content appear to occur rapidly following brief periods of disuse (2wks) and after subsequent active recovery (4wks) in young and old, which contribute to alterations in contractile function at the single muscle fiber level. Changes in myosin content appear to occur independently of age, while influenced by fiber type (MHC isoform) in young but not old.

AB - Short-term disuse and subsequent recovery affect whole muscle and single myofiber contractile function in young and old. While the loss and recovery of single myofiber specific force (SF) following disuse and rehabilitation has been shown to correlate with alterations in myosin concentrations in young, it is unknown whether similar relationships exist in old. Therefore, the purpose of the present study was to examine the effect of 14days lower limb disuse followed by 28days of active recovery on single muscle fiber myosin content in old (68yrs) and young (24yrs) recreationally physically active healthy men. Following disuse, myosin content decreased (p<0.05) in MHC 1 (young -28%, old -19%) and 2a fibers (young -23%, old -32%). In old, myosin content decreased more (p<0.05) in MHC 2a vs 1 fibers. Following recovery, myosin content increased (p<0.05) and returned to pre-disuse levels for both young and old in both fiber types, with MHC 2a fibers demonstrating an overshooting in young (+31%, p<0.05) but not old. Strong correlations were observed between myosin content and single fiber SF in both young and old, with greater slope steepness in MHC 2a vs 1 fibers indicating an enhanced intrinsic contractile capacity of MHC 2a fibers. In conclusion, adaptive changes in myofiber myosin content appear to occur rapidly following brief periods of disuse (2wks) and after subsequent active recovery (4wks) in young and old, which contribute to alterations in contractile function at the single muscle fiber level. Changes in myosin content appear to occur independently of age, while influenced by fiber type (MHC isoform) in young but not old.

KW - Aged

KW - Aging/physiology

KW - Humans

KW - Immobilization/adverse effects

KW - Knee/physiology

KW - Male

KW - Muscle Contraction/physiology

KW - Muscle Fibers, Skeletal/metabolism

KW - Muscle Strength/physiology

KW - Muscular Atrophy

KW - Myosin Heavy Chains/metabolism

KW - Protein Isoforms/metabolism

KW - Time Factors

KW - Young Adult

U2 - 10.1016/j.exger.2016.10.009

DO - 10.1016/j.exger.2016.10.009

M3 - Journal article

C2 - 27794458

SN - 0531-5565

VL - 87

SP - 100

EP - 107

JO - Experimental Gerontology

JF - Experimental Gerontology

IS - Part A

ER -