ABSTRACT
The aim of the present study was to investigate changes in the mechanical characteristics of the rat epitrochlearis muscle as a result of a period of hyperactivity. A tail suspension model was used to impose postural activity in the forelimb musculature with the intention of inducing a relative slowness in the fast epitrochlearis muscle. A method of dual-controlled releases was used to obtain force-velocity and tension-extension relationships characterizing muscle mechanics. Results showed that: (1) mechanical characteristics are that of a fast-twitch muscle and (2) suspension induces a decrease in the maximal shortening velocity and a decrease in the compliance of series elastic elements. Changes in fibre type proportions are consistent with these mechanical adaptations. This demonstrates that an usual model of muscle hypoactivity can also be used for imposing hyperactivity of a postural nature, inducing muscle transformations towards a slower twitch muscle.
Subject(s)
Hindlimb Suspension , Muscle, Skeletal/physiology , Animals , Biomechanical Phenomena , Elasticity , Male , Muscle Contraction , Muscle Fibers, Fast-Twitch/physiology , Muscle Fibers, Fast-Twitch/ultrastructure , Muscle Fibers, Slow-Twitch/physiology , Muscle Fibers, Slow-Twitch/ultrastructure , Muscle, Skeletal/ultrastructure , Posture , Rats , Rats, Wistar , Weightlessness SimulationABSTRACT
Citrulline malate is known to improve performance in weakened muscles. The present experiment was designed to test the hypothesis that citrulline malate can limit the effect of endotoxins on muscle fatigability. Endotoxemia was induced in rats by injection of lipopolysaccharides from Klebsiella pneumoniae. Resistance to fatigue was quantified by measuring tension production during repetitive electrical stimulation of the isolated epitrochlearis muscle. Oral treatment by citrulline malate was found to increase resistance to fatigue in infected rats, whereas twitch tension was not modified. This demonstrates the efficacy of citrulline malate for limiting an increase in muscle fatigue elicited with bacterial endotoxins.
Subject(s)
Citrulline/analogs & derivatives , Malates/pharmacology , Muscle Fatigue/drug effects , Animals , Citrulline/pharmacology , In Vitro Techniques , Klebsiella pneumoniae , Lipopolysaccharides/toxicity , Male , Muscle Fatigue/physiology , Muscle, Skeletal/drug effects , Muscle, Skeletal/physiology , Rats , Rats, WistarABSTRACT
To test the hypothesis that endotoxins can directly modify muscle fatigue characteristics, in vitro experiments were performed on rat muscles 48 hours after injection of lipopolysaccharides (LPS) from Klebsiella pneumoniae. Resistance to fatigue was quantified by measuring tension production during repetitive electrical stimulation of the isolated epitrochlearis muscle. LPS treatment did not significantly modify initial force production whereas fatigability of the muscle was increased. This in vitro preparation should be used for testing antifatigue drugs.
