Affiliations: [a] Department of Physical Therapy, Sackler Faculty of
Medicine, Tel Aviv University, Israel. Tel.: +972 3 640 5589; Fax: +972 3 640
5436; E-mail: dlieberm@post.tau.ac.il | [b] Sport Technology Research Centre, Faculty of
Kinesiology, University of Calgary, Calgary, Canada
Note: [] Address for correspondence: Dario G. Liebermann, Ph.D.,
Department of Physical Therapy, Sackler Faculty of Medicine, Tel Aviv
University, P.O.B. 39040, Ramat Aviv, 69978 Israel
Abstract: Purpose: This study assessed the reliability and validity of
different methods used to estimate lower-limb muscular power capability based
on mechanical variables. For this purpose, vertical jumping was compared with
isokinetic knee extensions and with power tests used by practitioners. Methods: Four groups of subjects (N=106) were tested in different
conditions. Group-I performed countermovement vertical jumps (CMJ) on a force
plate followed by left and right knee extensions on an isokinetic device at
120, 180 and 240 deg · s^{-1}. Group-II performed CMJ trials
followed by 20-m sprints, hand-reach jumps and 1RM leg-press testing. Group-III
carried out squat jumps (SJ) in addition to CMJ trials. Finally, Group-IV
performed the CMJ test and was retested twice after a short inter-session
interval (1–4 days) and after a long one (4.5–5 months). The Pearson
correlation was used to assess the validity and reliability of CMJ (p ≤
0.01, **). Results: Mean peak power during CMJ was correlated with sprint time
(r=-0.882^{**}) and leg-press 1 RM
(r=0.797^{**}), but less with peak hand-reach height
(r=0.695; p ≤ 0.05). Isokinetic knee extension power showed also a
significant correlation with CMJ power, but its strength depended on the
angular velocity (Isok-120 r=0.702^{**}; Isok-180
r=0.737^{**}; Isok-240 r=0.599^{**}).
Test-retests showed a strong correlation after a short interval
(r=0.915^{**}) and after a long one
(r=0.890^{**}). Using the SJ technique did not have any
effect on reliability (r=0.914^{**}). Conclusions: CMJ matches other methods used for testing lower-limb
power capability. It is highly reliable and it allows a valid assessment of
muscular power. Since CMJ is also simple and accurate to perform, it is the
recommended method.
