Pliometric contraction-induced injury of mouse skeletal muscle:
effect of initial length.
Hunter, Kam D., and John A. Faulkner.
Department of Physiology and Institute of Gerontology, University
of Michigan, Ann Arbor, Michigan 48109-2007
APStracts 3:0432A, 1996.
For single pliometric (lengthening) contractions initiated from
optimal fiber length, the most important factor determining the
subsequent force deficit is the work input during the stretch. We
tested the hypothesis that regardless of the initial length, the
force deficit is primarily a function of the work input. Extensor
digitorum longus muscles of mice were maximally activated in situ and
lengthened at 2 Lf/sec from one of three initial fiber lengths (90%,
100%, or 120% of Lf) to one of three final fiber lengths (150%, 160%,
or 170% of Lf). Maximal isometric force production was assessed prior
to and following the pliometric contraction. No single mechanical
factor, including the work input (r2 = 0.34), was sufficient to
explain the differences in force deficits observed among groups.
Therefore, the force deficit appears to arise from a complex
interaction of mechanical events. With the data grouped by initial
fiber length the correlation between the average work and the average
force deficit was high (r2 = 0.97 to 0.99). Consequently, differences
in force deficits among groups were best explained on the basis of
the initial fiber length and the work input during the stretch.
Received 11 January 1996; accepted in final form 27 August 1996.
APS Manuscript Number A27-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996