Link to Original Research

James Redden, Keith Stokes, Sean Williams

Objectives

This study aimed to establish the reliability and meaningful change limits for single and double leg maximal strength, power, and bilateral imbalance measures in elite soccer players using a pneumatic resistance-based seated leg press.

Results

Thirteen elite soccer players underwent an incremental resistance leg press test on three separate occasions within a seven-day period. The study utilized the Keiser Air 420 seated leg press, with independent measurement of left and right leg power, to assess maximal resistance, velocity, force, average and peak power outputs, and imbalance variables.

• Reliability: The study found 'good' reliability (intra-class correlation coefficient, ICC > 0.762) and acceptable typical percentage errors (< 6.9%) across maximal resistance, velocity, force, and power output variables.
• Power Imbalance: Average power output across all repetitions was the most reliable measure of imbalance (ICC > 0.874), with absolute typical error values of 2.1%.
• Limits of Meaningful Change: The study established limits of meaningful change for strength, power, and imbalance variables to assist practitioners in evaluating test results accurately.

Summary

The Keiser Air 420 seated leg press provides a reliable method for assessing lower limb strength, power, and bilateral imbalances in elite soccer players. The findings offer practitioners valuable benchmarks for meaningful changes in athlete performance, facilitating targeted training interventions for strength enhancement and injury risk reduction.

Glossary

• Maximal Strength: The highest force an athlete can exert in one maximal effort.
• Power Output: The rate at which work is performed or energy is expended.
• Bilateral Imbalance: A discrepancy in strength or power between an athlete's left and right sides, which could influence performance and injury risk.

Journal of Sports Science and Medicine (2018) 17, 539-546