Construct Validity, Test-Retest Reliability, and Repeatability of Performance Variables Using a Flywheel Resistance
Lance M Bollinger1, Jason T Brantley, Justin K Tarlton
1Department of Kinesiology and Health Promotion, University of Kentucky, Lexington, Kentucky.
Journal of Strength and Conditioning Research
|October 26, 2020
Summary
Flywheel resistance training devices offer valid measures of power, force, and work. However, test-retest reliability and repeatability vary across exercises, suggesting familiarization is key for accurate performance assessment.
Area of Science:
- Sports Science
- Biomechanics
- Exercise Physiology
Background:
- Power production is crucial for athletic performance, yet quantifying it during resistance exercise remains challenging.
- Flywheel resistance training devices offer a potential solution for measuring power output.
- This study investigates the validity and reliability of a specific flywheel device.
Purpose of the Study:
- To determine the construct validity of flywheel-based performance testing.
- To assess the test-retest reliability and repeatability of performance variables measured by a flywheel device.
- To evaluate the accuracy of power, force, and work measurements across different exercises and inertia levels.
Main Methods:
- Twelve resistance-trained males performed exercises (bent-over row, Romanian deadlift, biceps curl) using a flywheel device (Exxentric kbox 4 Pro) with varying inertia.
- Measurements included average power, peak power (concentric and eccentric), average force, average speed, and total work over 3 sets of 5 maximal repetitions.
- Data were analyzed using regression, Pearson's correlation, Bland-Altman plots, and coefficient of repeatability.
Main Results:
- Regression analysis showed a near-perfect relationship between measured and predicted power, force, and work.
- Test-retest reliability was good to excellent (r ≥ 0.70) for most outcomes, except peak eccentric power in biceps curls (r = 0.69).
- Bland-Altman analysis indicated statistically significant bias (5-15%) for some measures, and high coefficients of repeatability suggested poor trial-to-trial consistency.
Conclusions:
- Flywheel-based performance testing demonstrates construct validity for measuring power, force, and work.
- Reliability and repeatability vary significantly between different exercises and specific outcome measures.
- Athletes unfamiliar with flywheel devices may need multiple testing sessions or a familiarization period for accurate results.
