The principles and clinical applications of isokinetic strength testing
Vedran Hadžić, University in Ljubljana, Faculty of Sport, Dept. of Sports Medicine
Abstract
Isokinetic strength evaluation is an important part of the comprehensive evaluation and rehabilitation of
the musculoskeletal system. Isokinetic testing provides us with essential information regarding (1) the
absolute and/or relative strength of the muscle groups of interest, (2) the existence of strength deficits
and (3) the existence of strength imbalances using either the conventional strength ratio:
Antagonistconc/Agonistconc or the dynamic control (also functional) ratio: Antagonistecc/Agonistconc. These
parameters have an important predictive value for lower or upper extremity injuries in the terms of injury
prevention and as a common objective clinical outcome measure to be used in evidence based
rehabilitation guidelines. This is best seen in ACL injuries where all major clinical guidelines [1, 2] suggest
isokinetic knee testing when making a clinical decision in regard to progression to the next phase of
rehabilitation or return to sport and/or ADL activities [3]. While isokinetic testing of the knee dynamic
stabilizers is well known, it is very important to highlight that isokinetic strength testing of the shoulder is
as equally informative and important as it enables us to evaluate both rotator cuff [4] and scapular
stabilizers [5]. Isokinetic testing has a special place in the area of sports medicine where isokinetic
strength parameters are used to predict the players at risk [6] for some important and frequent injuries
but also sports performance of healthy players (e.g. sprinting [7], vertical jumping [8, 9], overhead spiking
[10]). The open kinetic chain conditions provide excellent isolation of certain muscle groups and
ability of modern dynamometers to tightly control training loads and velocities makes them an
important strength-training tool in the treatment of tendinopathies and muscle strains (e.g hamstring
strains) [11]. Isokinetic dynamometry has evolved into important, objective, safe and reproducible
diagnostic tool in rehabilitation and sports medicine and it is becoming increasingly popular and
important in training as well. To utilize the most from such advanced diagnostic tool it is important to
choose adequate testing protocol that has a good sensitivity and specificity, and one must be aware
that the protocol may differ based on the clinical endpoint.
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