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14th annual Congress ECSS 2009, Oslo, Book of Abstracts, 2009;

Intersession Reliability of Vertical Jump Height

Year: 2009



The usefulness of measurements in research depends on the extent to which the researcher can rely on data as accurate and meaningful indicators of a behavior. In short, the measurements have to be reliable and valid (Portney and Watkins, 2008). The vertical countermovement jump (CMJ) is often used as a physical performance test. Researchers routinely seek to enhance the reliability of the CMJ height measurement by having subjects perform a number of jumps, typically 3 or 5, and then using either the best or the average for further analyses. However, studies show that there does not exist a consistent protocol for either the number of jumps or whether to use best of or average (e.g. Bazett-Jones et al., 2008, Vanezis and Lees, 2005, Hamilton, 2008). The purpose of this study is to investigate how the number of jumps and the use of best of or average affect the reliability of the CMJ measurements.
Twenty-two males (25.2 +/- 1.95 years; 1.81 +/- 0.06 meters; 75.9 +/- 6.38 kg [mean +/- SD]) went through the same programme twice (test and retest) with one week in between. The programme started with five minutes warm-up on a cycle ergometer followed immediately by 10 maximal CMJs on a force plate with one minute rest before each jump. From the data, 4 series of 10 testretest intraclass correlation coefficients (ICC) were calculated. In two series, A and B, jump height was calculated from the vertical impulse, while jump height in the other two series (C+D) was calculated from flight time. The first ICC in each series (A-D) was calculated from the first jump in test and retest. The second ICC in series A+C was calculated from the average of the two first jumps in test and retest, and in series B+D from the best of the two first jumps in test and retest. The same procedure was used for the third ICC and so on until the tenth ICC where all the 10 jumps from test and retest were used in the ICC calculations.
The series A, which was calculated from the vertical impulse and using the average, gave the following ICCs: 1 jump = 0.74; 2 jumps = 0.82; 3 jumps = 0.86; 10 jumps = 0.91. The series B, C and D had lower ICCs and in that order.
The results showed three things: (1) It is more reliable to use vertical impulse than flight time, (2) it is more reliable to use average than best of, and (3) ICC increased steeply through the first three jumps and then just slightly. Therefore, when using the CMJ as a physical performance test, one should use vertical impulse and average of at least 3 jumps.
Portney, L, Watkins, M. (2008). Foundation of Clinical Research. Application to Clinical Practice, p. 77, Pearson Prentice Hall, New Jersey.
Bazett-Jones DM, Gibson MH, McBride JM. (2008). J Strength Cond Res, 22(1), p. 25-31.
Vanezis A, Lees AD. (2005). Ergonomics, 48, p. 1594-1603.
Hamilton RT, Shultz SJ, Schmitz RJ, Perrin DH. (2008). J Athl Train, 43(2), p. 144-151.

GID: 2120; Last update: 25.12.2009