Similar acute molecular responses to equivalent volumes of isometric, lengthenin

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J Appl Physiol. 2006 Sep 28

Similar acute molecular responses to equivalent volumes of isometric,

lengthening or shortening mode resistance exercise.

Garma TM, Kobayashi CA, Haddad F, GR, Bodell PW, Baldwin KM.

Physiology and Biophysics, University of California, Irvine, Irvine,

California, United States.

The present study was undertaken to test the hypothesis that the

contraction mode of action (static - isometric [iSO], shortening -

concentric [CON], or lengthening- eccentric [ECC]) used to stress the

muscle provides a differential mechanical stimulus eliciting greater

or lesser degrees of anabolic response at the initiation of a

resistance training program. We performed an acute resistance

training study in which different groups of rodents completed four

training sessions in either the ISO, CON or ECC mode of contraction

under conditions of activation and movement specifically designed to

elicit equivalent volumes of force accumulation. T

he results of this experiment indicate that the three modes of

contraction produced nearly identical cell signaling indicative of an

anabolic response involving factors such as: increased levels of mRNA

for insulin-like growth factor -I (IGF-I), pro-collagen III alpha1,

decreased myostatin mRNA and increased total RNA concentration. The

resulting profiles collectively provide evidence that pure mode of

muscle action, in-and-of itself, does not appear to be a primary

variable in determining the efficacy of increased loading paradigms

with regard to the initiation of selected muscle anabolic responses.