Maximum Strength and Ratio of Leg Extension and Leg Flexion in Elite Soccer Players. A Comparison of an Open Versus Closed Isokinetic System

The functional condition of the leg muscles is not only relevant to performance in sports, but is also of great importance in health, prevention and rehabilitation, where not only the general strength level is decisive but also the relationship between individual muscle groups. Among other things the H-Q-ratio (strength ratio of "hamstring" muscles to quadriceps muscles) is often used to diagnose possible imbalances. Isokinetic force measurements have established themselves as the gold standard in competitive football. In this context, however, force tests in the open kinetic chain (OKC) have almost exclusively been used so far. Especially force measurements in the closed kinetic chain (CKC) could have a higher relevance regarding functionality. The H-Q-ratio should better be called the flex-ext-ratio in the CKC due to the involvement of the hip muscles. There is little data in the literature on leg force or flex-ext-ratio in CKC. In particular, there is hardly any comparative data for isokinetic measurement systems in the CKC. Using a cross over design and randomly allocating 28 competitive football players into two groups (n=14 each) that either started tests with the leg press or legcurl device, the investigators assumed (1) a significantly lower flex-ext-ratio in the CKC compared to the OKC, (2) a correlation between the isokinetic measurement systems in the OKC and the CKC, and (3) a significant superiority of the leg press to predict functional performance of the lower limbs.