Kd. Hunter et Ja. Faulkner, PLIOMETRIC CONTRACTION-INDUCED INJURY OF MOUSE SKELETAL-MUSCLE - EFFECT OF INITIAL LENGTH, Journal of applied physiology, 82(1), 1997, pp. 278-283
For single pliometric (lengthening) contractions initiated from optima
l fiber length (L(f)), the most important factor determining the subse
quent force deficit is the work input during the stretch. We tested th
e hypothesis that regardless of the initial length, the force deficit
is primarily a function of the work input. Extensor digitorum longus m
uscles of mice were maximally activated in situ and lengthened at 2 L(
f)/s from one of three initial fiber lengths (90, 100, or 120% of L(f)
) to one of three final fiber lengths (150, 160, or 170% of L(f)). Max
imal isometric force production was assessed before and after the plio
metric contraction. No single mechanical factor, including the work in
put (r(2) = 0.34), was sufficient to explain the differences in force
deficits observed among groups. Therefore, the force deficit appears t
o 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 (r(2) = 0.97-0.99). Conseq
uently, differences in force deficits among groups were best explained
on the basis of the initial fiber length and the work input during th
e stretch.