What is the best method for assessing lower limb force-velocity relationship?

Area of Science:

• Biomechanics
• Sports Science
• Exercise Physiology

Background:

• Accurate measurement of kinetic variables like force, velocity, and power is crucial for performance analysis and training monitoring in sports.
• Various technologies, including accelerometry, linear position transducers, and specific calculation methods, aim to provide these measurements.
• Understanding the validity and reliability of these methods under different loading conditions is essential for practical application.

Purpose of the Study:

• To determine the concurrent validity and reliability of accelerometry, linear position transducer, and Samozino's methods for measuring force, velocity, and power during loaded squat jumps.
• To compare these methods against a gold standard (force plate) across a range of external loads.
• To assess the suitability of these methods for tracking training-induced changes.

Main Methods:

• Seventeen subjects performed loaded squat jumps under seven different loading conditions (0-60% of maximal concentric load) on two separate occasions.
• Force, velocity, and power were calculated using accelerometry, linear position transducer, and Samozino's method, and compared to force plate data.
• Statistical analyses included concurrent validity (agreement) and reliability (Intraclass Correlation Coefficient - ICC, coefficient of variation - CV).

Main Results:

• All tested methods demonstrated very good concurrent validity with the reference force plate measurements (CV=6.4-14.5%).
• While generally in agreement, slight differences were noted for high-velocity movements.
• Mean force, velocity, and power measurements were found to be reliable across all methods (ICC=0.84-0.99), with Samozino's method showing the highest reliability (CV=2.7-8.6%).

Conclusions:

• Accelerometry, linear position transducer, and Samozino's methods are valid and reliable tools for assessing force, velocity, and power during squat jumps across various loading conditions.
• These methods are suitable for between-session comparisons and monitoring training adaptations.
• Linear position transducer and accelerometer capture the full kinetic pattern, while Samozino's method offers superior reliability and simpler data processing.