Poster Session III, July 15th 2010 — Abstracts Sampling rate influence on vertical jump height in force plate analysis

Jump analyses are often used in performance diagnostic and scientific research. Usually vertical ground reaction forces are measured to calculate jump height. There are different types of force plates and varying sampling rates. Generally calculation of jump height based on impulse-momentum or flight time method. This study investigates the influence of different sampling rates in filtered and non-filtered force signals on the jump height calculated with impulse-momentum and flight time method. For the study we used vertical ground reaction forces of 60 counter movement jumps (CMJ) performed by 20 professional soccer players. Forces are measured with two force plates (Kistler). Sampling rate was set to 1000 Hz. Curves are used non-filtered and filtered (Butterworth) and were downsampled to 500 Hz, 200 Hz and 100 Hz. The jump height was calculated with a customized program designed using LABVIEW (National Instruments). Body weight was calculated with the impulse momentum method of the whole jump time. Numerical integration method was the trapezoidal rule. Differences between groups were tested with a oneway repeated measures ANOVA and carried out with Bonferroni correction (p≤0.05). Jump height decreased significant with downsampling force curves for impulse-momentum and flight time method and filtered and non-filtered condition. Mean changes between 1000 and 500 Hz were 0.1–0.2 cm, between 1000 and 200 Hz 0.5–0.6 cm and between 1000 and 100 Hz 1.3–1.5 cm. There are no differences between jump height (impulse-momentum method) in filtered and non-filtered condition at 1000, 500, 200 and 100 Hz. In flight time method filtering the force curves decreased the jump height. The decrease in jump height after downsampling force time curves maybe an influencing factor of different results described in literature. Especially between 1000 and 100–200 Hz the differences have practical relevance. The influence in other parameters like landing peak force can be much greater. The use of a filter before calculation jump height seems to be uncritical for impulsemomentum method. In flight time method the influence of filtering is low and certainly lesser than other factors like force threshold or landing style. Filtering and especially sampling rate have to be considered in every study with the use of force plates.