Intersession Reliability of Three Devices Used to Measure Countermovement Vertical Jump Height

Abstract

PURPOSE: The purpose of this investigation was to assess the intersession reliability of three devices that are commercially-available to measure countermovement vertical jump (CMJ) height. METHODS: Forty male and 39 female university students completed three maximal-effort CMJs during two testing sessions, which were separated by 24–48 hours. The height of the CMJ was measured from the three devices simultaneously. Device one (D1) was a jump-and-reach apparatus, device two (D2) was a contact mat, and device three (D3) was an accelerometer. For each device, systematic error in the CMJ height measurement was assessed using a dependent t-test. Relative reliability was assessed using an intraclass correlation coefficient (ICC), and absolute reliability was assessed using the standard error of measurement (SEM), coefficient of variance (CV), and limits of agreement. Also, the level of heteroscedasticity associated with each device was assessed by calculating the correlation coefficient between the maximal CMJ heights of each subject and the maximal CMJ height absolute differences between session one and session two of each subject. RESULTS: For all three devices, no systematic error was discovered (p > 0.05) when the maximal CMJ heights from the two sessions were compared. In males, D3 demonstrated the best intersession reliability (ICC = 0.88; SEM = 2.4cm; CV = 5.3%; limits of agreement = −0.08 ± 4.06cm), followed by D1 (ICC = 0.90; SEM = 3.0cm; CV = 5.9%; limits of agreement = −0.26 ± 8.27cm), and then D2 (ICC = 0.84; SEM = 3.6cm; CV = 6.3%; limits of agreement = 0.15 ± 7.13cm). In females, D3 demonstrated the best intersession reliability (ICC = 0.92; SEM = 1.3cm; CV = 4.1%; limits of agreement = 0.33 ± 3.53cm), followed D2 (ICC = 0.92; SEM = 1.7cm; CV = 4.4%; limits of agreement = 0.45 ± 4.74cm), and then D1 (ICC = 0.80; SEM = 2.7cm; CV = 8.6%; limits of agreement = −0.30 ± 7.66cm). Additionally, the CMJ height measurement demonstrated heteroscedasticity regardless of the device used to quantify the measurement. CONCLUSIONS: D3 demonstrated the best intersession reliability for measuring CMJ height in males and females. Furthermore, in both males and females, heteroscedasticity appears to be a natural phenomenon for the CMJ height measurement. This indicates that better jumpers demonstrate greater fluctuation in the maximal CMJ height measurement when the measurements are taken over two testing sessions separated by 24–48 hours. PRACTICAL APPLICATIONS: The jump-and-reach apparatus and contact mat are commonly used to assess CMJ height because they are easy to operate and provide immediate results. However, the current study has demonstrated that CMJ height measured from an accelerometer, which is also easy to operate while providing immediate results, tends to be more reliable. Consequently, the accelerometer may be better suited to detect real changes in CMJ height after participation in a training program.