Reliability of Kinematic and Kinetic Measures of Jump Performance Using Accelerometry

Abstract

PURPOSE: The purpose of this study was to determine the reliability of kinetic and kinematic variables measured from bilateral and unilateral countermovement and drop jumps using an accelerometer. METHODS: Twenty six subjects with mean age, height, and weight of 21 ± 1.2 years, 179.3 ± 9.9 cm, and 82.18 ± 16.2 kg, respectively completed the study. After a 5-minute warm up and dynamic stretches, the following jumps were completed in random order with a 30-second rest period between each trial: bilateral countermovement vertical jump (BCV), bilateral countermovement horizontal jump (BCH), bilateral 40 cm drop vertical jump (BDV), bilateral 40 cm drop horizontal jump (BDH), unilateral countermovement vertical jump (UCV), unilateral countermovement horizontal jump (UCH), unilateral 20 cm drop vertical jump (UDV), and unilateral 20 cm drop horizontal jump (UDH). An accelerometer (Inform Sport Training Systems, Victoria, BC. Canada), worn at the waist, measured the following jump kinematics: jump height, ground contact time, concentric time, time to peak concentric force, time to peak power, and reactive strength (jump height divided by ground contact time). Kinetic measures included mean concentric force, peak concentric force, and peak power. Jump distance during the horizontal jumps was measured using a tape measure. After completing all jumps in one session, a minimum of 48 hours of rest was allowed before repeating the jumps in a second session. The best of 3 trials was recorded for analysis. The ground contact recorded for analysis was taken from the highest reactive strength found during the drop jumps. The Pearson r was used as a measure of relative reliability (between-subject variation) and the coefficient of variation (cv), expressed as a percent, determined absolute reliability (within-subject variation) after test-retest procedures. RESULTS: Relative reliability was high ( 0.69 ≤ r ≤ 0.93) for all of the bilateral vertical jump variables while jump height, mean concentric force, and peak concentric force during the BCV and jump height during BDV was found to produce moderate to high absolute reliability with a range between 3.7–9.4%. Relative reliability ranged from moderate to high ( 0.5 ≤ r ≤ 0.96) for the unilateral vertical jump variables while the CV for jump height (8.3%) and peak concentric force (9.2%) during the UCV demonstrated moderate absolute reliability. High relative (r = 0.96 and 0.94) and absolute reliability (cv = 3.3 and 4.4%) was found for jump distance during the BCH and BDH, respectively while reactive strength during the BDH produced moderate relative (r = 0.67) and low absolute (cv = 15.3%) reliability. Similar results were found for the unilateral horizontal jumps. Jump distance demonstrated high relative (r = 0.91 and 0.91) and absolute (cv = 4.8 and 6.3%) reliability during the UCH and UDH, respectively while reactive strength during the UDH demonstrated moderate (r = 0.62) and low (cv = 19%) reliability. Conclusion: The best overall reliable measures were jump height and distance while reactive strength demonstrated moderate to low reliability. All other variables, except for ground time during the unilateral jumps, produced high and significant relative reliability but low absolute reliability. Practical Application: The data indicate that the variables can be used to rank subjects but, beside jump height and distance, do not provide enough within-subject accuracy to monitor improvement.