Modifiability of residual force depression in single muscle fibers following uphill and downhill training in rats

The increase and decrease in steady-state isometric force following active muscle lengthening and shortening are referred to as residual force enhancement (RFE) and force depression (FD), respectively. The RFE and FD states are associated with decreased (activation reduction; AR) and increased (activation increase; AI) neuromuscular activity, respectively. Although the mechanisms have been discussed over the last 60 years, no studies have systematically investigated the modifiability of RFE and FD with training. The purpose of the present study was to determine whether RFE and FD could be modulated through eccentric and concentric biased resistance training. Fifteen healthy young adult men (age: 24 ± 2 yr, weight: 77 ± 8 kg, height: 178 ± 5 cm) underwent 4 wk of isokinetic dorsiflexion training, in which one leg was trained eccentrically (−25°/s) and the other concentrically (+25°/s) over a 50° ankle excursion. Maximal and submaximal (40% maximum voluntary contraction) steady-state isometric torque and EMG values following active lengthening and shortening were compared to purely isometric values at the same joint angles and torque levels. Residual torque enhancement (rTE) decreased by ~36% after eccentric training ( P < 0.05) and increased by ~89% after concentric training ( P < 0.05), whereas residual torque depression (rTD), AR, AI, and optimal angles for torque production were not significantly altered by resistance training ( P ≥ 0.05). It appears that rTE, but not rTD, for the human ankle dorsiflexors is differentially modifiable through contraction type-dependent resistance training. NEW & NOTEWORTHY The history dependence of force production is a property of muscle unexplained by current cross bridge and sliding filament theories. Whether a muscle is actively lengthened (residual force enhancement; RFE) or shortened (force depression) to a given length, the isometric force should be equal to a purely isometric contraction—but it is not! In this study we show that eccentric training decreased RFE, whereas concentric training increased RFE and converted all nonresponders (i.e., not exhibiting RFE) into responders.

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Reminiscences of My Early Work: II. Transverse Spread of Contraction Initiated by Local Membrane Depolarization in Single Muscle Fibers

Mysteries in Muscle Contraction ◽

10.1201/b22329-13 ◽

2017 ◽

pp. 203-239

Author(s):

Haruo Sugi

Keyword(s):

Muscle Fibers ◽

Membrane Depolarization ◽

Single Muscle

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DISSECTION AND ELECTROPHORETIC PROTEIN ANALYSIS OF SINGLE MUSCLE FIBERS FROM HISTOLOGICALLY IDENTIFIED FREEZE-DRIED SECTIONS: APPLICATION TO MUSCLE FIBERS WITH RIMMED VACUOLES

Biomedical Research ◽

10.2220/biomedres.4.459 ◽

1983 ◽

Vol 4 (5) ◽

pp. 459-466 ◽

Cited By ~ 2

Author(s):

ITARU TOYOSHIMA ◽

KEIKO TANAKA ◽

NOBUYOSHI FUKUHARA ◽

TOSHIHIDE KUMAMOTO ◽

TADASHI MIYATAKE

Keyword(s):

Muscle Fibers ◽

Protein Analysis ◽

Single Muscle ◽

Freeze Dried

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Contraction-induced injury to single muscle fibers: velocity of stretch does not influence the force deficit

AJP Cell Physiology ◽

10.1152/ajpcell.1998.275.6.c1548 ◽

1998 ◽

Vol 275 (6) ◽

pp. C1548-C1554 ◽

Cited By ~ 35

Author(s):

Gordon S. Lynch ◽

John A. Faulkner

Keyword(s):

Null Hypothesis ◽

Muscle Injury ◽

Isometric Force ◽

Muscle Fibers ◽

Single Muscle ◽

Control Value ◽

Severity Of Injury ◽

Before And After ◽

The Difference ◽

Permeabilized Fibers

We tested the null hypothesis that the severity of injury to single muscle fibers following a single pliometric (lengthening) contraction is not dependent on the velocity of stretch. Each single permeabilized fiber obtained from extensor digitorum longus muscles of rats was maximally activated and then exposed to a single stretch of either 5, 10, or 20% strain [% of fiber length ( L f)] at a velocity of 0.5, 1.0, or 2.0 L f /s. The force deficit, the difference between maximum tetanic isometric force (Po) before and after the stretch expressed as a percentage of the control value for Po before the stretch, provided an estimate of the magnitude of muscle injury. Despite a fourfold range from the lowest to the highest velocities, force deficits were not different among stretches of the same strain. At stretches of 20% strain, even an eightfold range of velocities produced no difference in the force deficit, although 40% of the fibers were torn apart at a velocity of 4 L f /s. We conclude that, within the range of velocities tolerated by single permeabilized fibers, the severity of contraction-induced injury is not related to the velocity of stretch.

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MHC and sarcoplasmic reticulum protein isoforms in functionally overloaded cat plantaris muscle fibers

Journal of Applied Physiology ◽

10.1152/jappl.1996.80.4.1296 ◽

1996 ◽

Vol 80 (4) ◽

pp. 1296-1303 ◽

Cited By ~ 31

Author(s):

R. J. Talmadge ◽

R. R. Roy ◽

G. R. Chalmers ◽

V. R. Edgerton

Keyword(s):

Sarcoplasmic Reticulum ◽

Heavy Chain ◽

Muscle Fibers ◽

Protein Isoforms ◽

Type I ◽

Single Muscle ◽

Plantaris Muscle ◽

Plasmic Reticulum ◽

Deep Region ◽

Isoform Expression

To determine whether the adaptations in myosin heavy chain (MHC) isoform expression after functional overload (FO) are accompanied by commensurate adaptations in protein isoforms responsible for relaxation [sarco(endo)plasmic reticulum (SR) Ca(2+)-adenosinetriphosphatase (SERCA) and phospholamban (PHL)] in single muscle fibers, the isoforms of MHC and SERCA and the presence or absence of PHL were determined for cat plantaris fibers 3 mo after FO. In control plantaris the relative MHC isoform composition was 23% type I, 21% type IIa, and 56% type IIb. FO resulted in a shift toward slower isoforms (33% type I, 44% type IIa, and 23% type IIb). In the deep region of the plantaris the proportions of type I MHC and hybrid MHC fibers (containing type I and II MHCs) were 40 and 200% greater in FO cats, respectively. FO resulted in a 47% increase in the proportion of fibers containing only the slow SERCA isoform (SERCA2) and a 41% increase in the proportion of fibers containing PHL. The proportions of fibers containing type I MHC, SERCA2, and PHL in control and FO plantaris were linearly correlated. These data show that adaptations in MHC isoform expression are accompanied by commensurate adaptations in sarcoplasmic reticulum protein isoforms in single muscle fibers after FO.

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