What is isokinetic testing?
Isokinetic testing is fundamental to evaluate muscle performance and to prevent lower limb injuries. Often utilized to measure the concentric or eccentric force of the quadricep and hamstring muscles, isokinetic testing can also provide additional parameters to further explore muscular functionality, among them, the peak moment of force, i.e., the maximum strength the subject expresses during exercise. Another important application pertaining to isokinetic testing, is the comparison between the muscles of the two limbs which can highlight eventual asymmetries, leading in turn to the insurgence of muscle pathologies, usually at the expense of the flexors.
Risk factors in muscle injuries
According to recent studies on the epidemiology of sports injuries the injury which has by far, the greatest incidence among muscle-tendon injuries, concerns knee flexors.
Among inherent risk factors concerning thigh muscle injuries, we should mention first the effect of the dominance of a limb over another and second, the muscle imbalance between knee extensors and flexors.
Logically, the act of favoring, when exerting athletic gestures predicted by the performance model, a limb over the contralateral limb results in a greater risk of incurring in acute injuries and “overuse” injuries. As it is known, a reduced level of muscle strength and/or an imbalance are common risk factors, especially when it comes to hamstrings.
Hamstrings and muscle imbalance
Moreover, data shows that the correct conventional ratio between the concentric strength of Q and H (with regulatory data based on different authors and different operating speeds) should be between 0,6 e 0,7 and that, in this case, it can constitute a protective factor for the flexor muscles.
The rationale justifying such a hypothesis is that hamstrings’ muscles with an insufficient degree of strength cannot contrast the bending of the hip and the contextual extension of the leg on the thigh during the various sport specific gestures.
The so-called “working relationship” was introduced specifically to evaluate hamstrings’ function.
The functional H/Q is defined as the ratio between the torque peak of H during an eccentric contraction and the strength peak of Q during a concentric contraction.
Numerous studies demonstrate how asymmetries or imbalances in the H/Q functional ratio, known in the literature as “muscle imbalance”, can significantly influence muscle injuries’ incidence.
The role of the isokinetic method
However, note that the angular speed rates used during isokinetic testing are very different from the ones we have during natural activation.
Nonetheless, the isokinetic method in eccentric mode has been scientifically proven for what concerns both the prevention and the rehabilitation of hamstrings injuries.
Moreover, its easy replicability makes isokinetic an excellent method to test the strength capacity of hamstrings and to verify the ratios between flexor and extensor muscles of the leg on the thigh.
Dott. G. Martelli, sport medicine doctor
