Relationship Between Explosive Strength Capacity of the Knee Muscles and Deceleration Performance in Female Professional Soccer Players

The present study aimed to investigate the relationship between linear deceleration performance and explosive strength capacity of the knee muscles. Fourteen female professional soccer players completed the maximal sprint deceleration tests and knee flexor (KF) and knee extensor (KE) isokinetic concentric (240 degrees and 60 degrees.s(-1)) and eccentric contractions (30 degrees.s(-1)). Linear deceleration performance was evaluated from horizontal breaking force (F-H), power (P-H), and impulse (I-H) during a maximal linear deceleration. The peak torque (PT) of KF and KE, PT ratio between KF and KE (conventional and functional H/Q ratio), rate of torque development (RTD) for each muscle group, and RTD between KF and KE (RTD H/Q) were extracted from the isokinetic contractions. Pearson's correlation coefficients revealed that the eccentric (30 degrees.s(-1)) and concentric (60 degrees.s(-1), 240 degrees.s(-1)) KE peak torque, and the concentric KF peak torque (240 degrees.s(-1)) were significantly correlated with F-H, P-H, and I-H (-0.75<r<-0.54). Moreover, a significant correlation was found between KE RTD during eccentric contraction and F-H, P-H, and I-H (-0.63<r<-0.54). Besides, a significant correlation was observed between RTD H/Q at 60 degrees.s(-1) and P-H, I-H (-0.61<r<-0.57). No significant relationship was observed between the H/Q ratio, KF RTD and deceleration performance. These main findings indicated the importance of the ability to quickly produce high KE eccentric torque, contributing to braking force production. Meanwhile, RTD H/Q should be assessed for its essential role in knee joint dynamic stability and can be a relevant index to determine deceleration performance.