TY - JOUR
T1 - The fiber-type-specific effect of inactivity and intermittent weight- bearing on the gastrocnemius muscle of 30-month-old rats
AU - Sandmann, Michael E.
AU - Shoeman, Janice A.
AU - Thompson, LaDora V
PY - 1998/6
Y1 - 1998/6
N2 - Objective: To characterize single skeletal muscle fiber contractile properties from the gastrocnemius muscle that occur during inactivity and intermittent weight-bearing in 30-month-old animals. Design: Randomized control trial. Setting: A controlled laboratory environment. Subjects: Eighteen 30-month-old male Fisher 344 Brown Norway F1 Hybrid rats were randomly assigned to control (C), hindlimb unweighted (HU), and hindlimb unweighted with intermittent weight-bearing (HU-X) groups. Interventions: The HU and HU-X rats were suspended for 7 days. The HU-X animals were unsuspended for four 15-minute bouts of weight-bearing. Main Outcome Measures: Single skeletal muscle fiber contractile properties (diameter, peak active force [P0], peak specific tension [P0/CSA], and maximal shortening velocity [V0] by fiber type) were determined from the deep portion of the lateral head of the gastrocnemius muscle (RG). Results: In comparison to C animals, the ratio of gastrocnemius weight to body weight decreased by 18% and 14% following HU and HU-X, respectively. Diameter and P0 of type I fibers from the RG were reduced after HU. Attenuation of the decline in diameter and P0 was observed in type I fibers from the RG with HU-X. P0 was reduced in type IIa fibers and type I-IIa fibers with HU. Attenuation of the decline in P0 by intermittent weight-bearing in type IIa fibers and type I-IIa fibers did not occur. Conclusions: Inactivity altered the contractile properties of single skeletal muscle fibers from the gastrocnemius muscle of 30-month-old animals. The inactivity-induced alterations were present in the three fiber types. Therapeutic intervention of weight-bearing attenuated the inactivity-induced changes in the type I fibers from the gastrocnemius, but not the other fiber types.
AB - Objective: To characterize single skeletal muscle fiber contractile properties from the gastrocnemius muscle that occur during inactivity and intermittent weight-bearing in 30-month-old animals. Design: Randomized control trial. Setting: A controlled laboratory environment. Subjects: Eighteen 30-month-old male Fisher 344 Brown Norway F1 Hybrid rats were randomly assigned to control (C), hindlimb unweighted (HU), and hindlimb unweighted with intermittent weight-bearing (HU-X) groups. Interventions: The HU and HU-X rats were suspended for 7 days. The HU-X animals were unsuspended for four 15-minute bouts of weight-bearing. Main Outcome Measures: Single skeletal muscle fiber contractile properties (diameter, peak active force [P0], peak specific tension [P0/CSA], and maximal shortening velocity [V0] by fiber type) were determined from the deep portion of the lateral head of the gastrocnemius muscle (RG). Results: In comparison to C animals, the ratio of gastrocnemius weight to body weight decreased by 18% and 14% following HU and HU-X, respectively. Diameter and P0 of type I fibers from the RG were reduced after HU. Attenuation of the decline in diameter and P0 was observed in type I fibers from the RG with HU-X. P0 was reduced in type IIa fibers and type I-IIa fibers with HU. Attenuation of the decline in P0 by intermittent weight-bearing in type IIa fibers and type I-IIa fibers did not occur. Conclusions: Inactivity altered the contractile properties of single skeletal muscle fibers from the gastrocnemius muscle of 30-month-old animals. The inactivity-induced alterations were present in the three fiber types. Therapeutic intervention of weight-bearing attenuated the inactivity-induced changes in the type I fibers from the gastrocnemius, but not the other fiber types.
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U2 - 10.1016/S0003-9993(98)90040-5
DO - 10.1016/S0003-9993(98)90040-5
M3 - Article
C2 - 9630145
AN - SCOPUS:0031749373
SN - 0003-9993
VL - 79
SP - 658
EP - 662
JO - Archives of Physical Medicine and Rehabilitation
JF - Archives of Physical Medicine and Rehabilitation
IS - 6
ER -