Feasibility and Reliability of the My Jump 2 Smartphone Application in Measuring Peak Power, Flight Time and Jump Height in Physically Active Subjects during Two Different Jumping Tasks

Muscle strength and power are often evaluated through jumping tasks. This study investigates the reliability of My Jump 2 (MJ2), a smartphone application (app) used for this assessment. Two commonly used jumps, the countermovement jump (CMJ) and squat jump (SJ), were analyzed. The study aimed to evaluate the reliability of MJ2 for assessing peak power, jump height, and flight time. Materials and Methods: Thirty-eight undergraduate students performed three jumps of each type in a randomized order. All jumps were executed on a contact mat and simultaneously recorded by the smartphone’s slow-motion camera. Two independent researchers analyzed the video data by identifying take-off and landing frames to calculate flight time. The intra-class correlation coefficient (ICC), coefficient of variation (CV), and Lin’s concordance correlation coefficient (CCC) were used for comparison. Results: Excellent reliability (ICC > 0.9) and high agreement were observed for flight time and jump height in both SJ and CMJ. Typical error and CV analysis indicated low variability for SJ, whereas CMJ jump height showed greater variability. However, peak power reliability and agreement were low (ICC < 0.5) for both jumps. Conclusions: The results suggest that MJ2 is a reliable and valid tool for assessing jump height and flight time, irrespective of the device used for data analysis. However, its power measurement capability differs from a contact platform’s, likely due to the indirect methods used to estimate power. Based on these findings, the MJ2 app can be confidently used to measure flight time and jump height but should be used cautiously when assessing power.