Maximal vs. explosive knee extensor strength in professional soccer players: inter‐limb asymmetries and relationship with knee function

Abstract

The main aims of this study were to compare the magnitude of inter-limb asymmetry (ILA) and the relation with self-reported knee function between maximal and explosive knee extensor strength outcomes in professional soccer players. Forty-six male soccer players completed different maximal isokinetic and isometric contractions of the knee extensors for the assessment of maximal strength (peak torque and maximal voluntary contraction (MVC) torque) and explosive strength (early, intermediate, late, and peak rate of torque development (RTD)). Self-reported knee function was assessed with the International Knee Documentation Committee (IKDC) and Lysholm knee scoring scales. Peak torque and MVC torque showed comparable ILAs (8-9%), both being significantly lower than all RTD ILAs (16% on average; p < 0.001). ILAs for early RTD (21%) and peak RTD (19%) were significantly higher than all the other variables (p < 0.05). Only early and intermediate RTD were significantly correlatedthough weaklywith both IKDC (rho = 0.32 for both) and Lysholm (rho = 0.36 and 0.30, respectively) scores. We conclude that explosive knee extensor strengthearly RTD in particularexhibited larger ILAs and better relations with self-reported knee function than peak torque and MVC torque in professional soccer players. These results confirm the validity and functional relevance of early RTD and the need for its inclusion in routine performance testing for soccer players. Highlights. Professional soccer players exhibited larger inter-limb deficits in knee extension strength for explosive actions than for the widely-used isokinetic test. . Self-reported knee function was significantly correlated with explosive strength of the knee extensor muscles but not with maximal strength. . The first 50 ms of an explosive knee extension seem to be crucial for self-perceived sport performance and possibly for injury prevention.

The Influence of Quadriceps Strength and Rate of Torque Development on the Recovery of Knee Biomechanics During Running After Anterior Cruciate Ligament Reconstruction

“…Because of differences in equipment, methodology (eg, joint angle), variable of interest (eg, RTD 20%-80% vs 0-100 ms from contraction onset), and study population, comparative healthy normative quadriceps RTD data for our after-ACLR population are not available in published literature. Mean quadriceps RTD LSI values of 86% to 88% for RTD epochs have been recorded in healthy professional soccer players 9 and professional/semiprofessional team and individual sport athletes, 45 similar to our analysis. Thus, our mean reported RTD LSI of 59.7% suggests significant impairment in involved limb rapid quadriceps torque development capacity (although we cannot rule out that nonsurgical limb RTD is also reduced, compared with a healthy control population).…”