Validity and Reliability of Strategy Metrics to Assess Countermovement Jump Performance using the Newly Developed My...

Area of Science:

• Biomechanics
• Sports Science
• Human Movement Analysis

Background:

• Accurate measurement of jumping performance is crucial in sports science.
• Smartphone applications offer potential for accessible and cost-effective performance analysis.
• Validation of new mobile-based biomechanical tools is essential before widespread adoption.

Purpose of the Study:

• To assess the validity and reliability of the My Jump Lab smartphone application.
• To evaluate the app's ability to measure jump height, time to take-off, and reactive strength index modified (RSI_Mod).
• To determine the impact of a correction factor on the accuracy of time to take-off and RSI_Mod measurements.

Main Methods:

• Twenty-seven postgraduate sport science students participated in the study.
• Participants performed three maximal effort countermovement jumps (CMJ) on twin force plates.
• Concurrent data collection using force plates and the My Jump Lab smartphone app.

Main Results:

• No significant differences were found for jump height (g = 0.00) or RSI_Mod (g = -0.49) between methods.
• Initial time to take-off showed a significant difference (g = 0.68), but this was resolved with a correction factor (g = 0.00).
• Bland-Altman analysis indicated near-perfect agreement for jump height and corrected time to take-off, with minimal bias for RSI_Mod.

Conclusions:

• The My Jump Lab app, with its embedded correction factor, is a valid and reliable tool for measuring countermovement jump performance.
• The app accurately quantifies jump height, time to take-off, and RSI_Mod, making it suitable for sport science applications.
• This smartphone-based approach provides a practical alternative for assessing key biomechanical jump variables.