| Secondary abstract: |
Introduction: One of the key motor abilities and a fundamental component of an individual's physical fitness is muscle strength, which can be objectively and accurately measured using laboratory and field tests. Assessing this attribute is particularly relevant when performing vertical jumps, which is, until today, most accurately measured with using force plates and motion capture systems in 3D space. However, these methods are often unsuitable for use, which opens the door to new methods, like the mobile application My Jump 2. Purpose: The purpose of this study is to determine the validity and reliability of lower limb strength measurements using the mobile application My Jump 2. Methods: The study involved 30 healthy participants, 25 women and 5 men. The jumps were performed on a force plate and simultaneously recorded using an iPhone 12 with the mobile application My Jump 2. Each participant performed four countermovement jumps. To assess measurement reliability, the testing was repeated after 48 hours. Results: The measured values of jump height, flight time, and muscle power obtained with mobile application My Jump 2 and force plate in both sessions, across four consecutive measurements, did not show statistically significant differences. The most frequent statistically significant differences were found between the measurements taken with mobile application My Jump 2 in both sessions and those taken with force plate. The same trend was observed for the average of the four measurements, the highest recorded values, and the median of the four consecutive measurements. Mobile application My Jump 2, compared to force plate, showed lower results based on averages in the first session: 0,7 cm for jump height, 0,01 s for flight time, and 349 W for muscle power. The intraclass correlation coefficient for the repeatability of jump height measurements ranged from 0,901 to 0,917, for flight time from 0,906 to 0,912, and for muscle power from 0,872 to 0,938. The correlation coefficient values indicated very good to excellent repeatability of the applied method. The correlation coefficient values for the reliability of mobile application My Jump 2 ranged from 0,829 to 0,922 for jump height, from 0,857 to 0,936 for flight time, and from 0,872 to 0,938 for muscle power, demonstrating very good to excellent reliability of the applied method. The measurements obtained with the mobile application My Jump 2 were also valid for assessing jump height, flight time, and muscle power. Discussion and conclusion: The mobile application My Jump 2 provides repeatable, valid, and reliable results for measuring jump height, flight time, and strength. It represents a cost-effective alternative to expensive laboratory equipment and is expected to become a standard method for assessing variables related to physical fitness and health in the future. |