| Determining
the reliability of a unilateral horizontal drop jump for displacement
provided the focus for this research. Eighteen male subjects were
required to step off a 20cm box and land on a force plate with one
leg and thereafter jump for maximal horizontal displacement on two
different days. Dependent variables from the jump assessment included
mean and peak vertical (V) and horizontal (H) ground reaction forces
(GRF) and impulses, horizontal displacement and contact time. The
between-trial variability of all kinematic and kinetic measures was
less than 7%. The most consistent measure over both trials was the
horizontal displacement jumped (1.2 to 1.4%) and the most variable
were the contact time the first day (6.5%) and peak HGRF the second
day (4.3%). In all cases there was less variation associated with
the second rather than the first day. In terms of test-retest variability
the percent changes in the means and coefficient of variations (CVs)
were all under 10%. The smallest changes in the mean (0.43 %), least
variation (< 2.26 %) and second highest intraclass correlation
co-efficient (ICC = 0.95) were found for horizontal displacement jumped.
The highest ICC (0.96) was found for horizontal impulse. Given the
reliability of the single leg drop jump, it may offer better prognostic
and diagnostic information than that obtained with bilateral vertical
jumps.
KEY
WORDS: Ground reaction force, impulse, assessment.
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