5e Journée Belge d’Isocinétisme
2 et 3 décembre 2005

Campus ERASME - Bruxelles


Isocinétisme et techniques d’évaluation de la fonction musculaire







Zeevi Dvir, PhD LLB, Dept. of Physical Therapy, Sackler Faculty of Medicine, Tel Aviv University, ISRAEL 69978


Muscular strength is not an absolute entity. It depends on the way it is being measured: statically or dynamically, concentrically or eccentrically. Obviously each of these measurement methods involves a large number of factors e.g. the joint position or the angular velocity during an isometric or an isokinetic test, respectively.


Among the operational parameters defining an isokinetic strength measurement protocol, the range of motion (RoM) and the preset velocity are of major importance. However so-called standard protocols prescribing these parameters have never been firmly adopted. Indeed studies relating to strength measurement of almost all major muscle groups reveal a wide diversity which precludes the establishment of representative data bases a serious problem which is further confounded by differences existing among various isokinetic dynamometers.


However the extent to which the isokinetic strength (peak torque) depends on a specific RoM has received very limited attention. Specifically, how do muscle strength scores vary when shorter than the commonly used RoMs are applied ? This problem is not trivial since limited RoM (LROM) testing offers a number of advantages. First, testing at a standard ROM may be unsafe and/or painful. For instance it has been indicated that patients suffering from hamstring strains had difficulty in exerting the initial torque necessary to counteract an external (eccentric) torque while in the most shortened position. Moreover, in the most elongated position these patients are at risk of re-straining the muscle during maximal eccentric testing (Croisier et al 2000, 2002). Other instances relate to contraindications for measuring isokinetic quadriceps strength. In patients during the earlier stages following anterior cruciate ligament reconstruction maximal testing near full extension (Paolos et al. 1983) may put the reconstructed ligament at risk. On the other hand, inclusion of the 60-90° knee motion sector may provoke severe pain in patients suffering from patellofemoral pain (Powers et al 1996, Thomee et al 1995). Thus testing within a range that is unlikely to compromise the relevant joint or muscles yet is capable of faithfully depicting muscle strength is a highly desirable objective. Second, problems associated with poly-centricity of joints (mechanical alignment) become significantly less involved when the joint in question is not allowed to move along a full RoM. Third, using an LROM in specific joint-muscle configurations invalidates the need to perform gravity correction procedures. Fourth, isokinetic testing which is LROM-based may be realized using simpler systems.


To challenge this problem a series of studies focusing on trunk and shoulder muscle groups was undertaken and reported before. The findings revealed excellent compatibility with those derived from so-called 'standard' RoMs. Specifically typical force-velocity characteristics were preserved as well as the eccentric/concentric strength ratios in both normal subjects (Dvir et al 2001, 2002) and chronic low-back patients (2003).


On going collaboration between the Universities of Liège and Tel Aviv is shedding further light on this issue. A recent isokinetic-EMG study of the knee extensors and flexors (Reichard et al 2005) indicated a very good agreement between the middle sector (30-60°) PT and the corresponding figure derived from the standard RoM (90°) in terms of absolute strength (particularly the concentric), within muscle eccentric to concentric strength ratios, between muscles (agonist to antagonist) strength ratios and the normalized IEMG (expressed in _V/Nm).


Yet unpublished results (Croisier et al 2005) also indicate that testing of knee muscles at short (30°) RoMs does not compromise the reproducibility either of the strength or EMG scores derived from the commonly used RoM of 90°. However, whereas strength was reproducible to within the accepted clinical standards, EMG scores require a far wider error band in order to indicate a meaningful variation.


In the framework of this joint project we also looked into LROM testing of patients following 1. reconstruction of the ACL as well as into isokinetic strength patterns of wrist flexors and extensors in 2. normal subjects and 3. patients following bone fractures in the territory of the wrist. Final results which were recently obtained with respect to (2) support the general finding namely that LROM testing is an efficient method for assessing isokeintic muscle strength.



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Croisier JL, Forthomme B, Namurois M, Vanderthommen M, Crielaard JM (2002) Hamstring muscle strain and performance disorders. Am J Sports Med 30: 199-203.

Croisier JL, Malnati M, Reichard LB, Peretz C, Dvir Z (2005) Isokinetic knee flexion and extension strength and electromyographic activity measured at different ranges of motion: A reproducibility study. Submitted for publication.

Dvir Z, Keating J (2001) The reproducibility of isokinetic trunk extension: A study using very short range of motion. Clin Biomech 16:627-630.

Dvir Z, Steinfeld-Cohen Y, Peretz C (2002) The identification of feigned isokinetic shoulder flexion weakness in normal subjects. Am J Phys Med Rehabil 81:178-183.

Dvir Z, Keating J (2003) Trunk extension strength and validation of trunk extension effort in chronic low-back dysfunction patients. Spine_28:685- 692.

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Reichard LB, Croisier JL, Katz-Leurer M, Malnati M, Dvir Z (2005) Testing knee extension and flexion strength at different ranges of motion: An isokinetic and electromyographic study, European Journal of Applied Physiology, in press.

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