Prof. Dvir’s Commentary:
It is not the intention of this writer to enhance his scientific contribution to the study of isokinetics through this channel but the paper selected for this month is quite unique in two respects: first, critical reviews regarding isokinetic dynamometry are not commonplace; second, the specific topic of this review concerns multiple-joint dynamometers known also as ‘closed chain’ or ‘linear’ machines. A search in the major scientific databases failed to indicate any prior review touching upon this important topic. Furthermore, it was the impression of both authors that this specific branch of isokinetics requires a thorough look as its application in scientific and clinical research is on the increase while some issues have not been accorded a proper consideration.
The review opens with an introduction to a new classification system for these dynamometers, taking into consideration their mechanical design, motion features and function. This classification is particularly missing, allowing confusion of truly linear dynamometers from those simulating linear by using curvilinear motion. Another chapter in the review relates to the employment of linear velocities and their relationship to their angular counterparts. Since one of the main objectives of multiple-joint motion is to produce linear trajectories of the end segment, e.g. that of the foot in leg-press or that of the hand in bench-press, the individual anatomical dimensions of the subject have a specific implication. In other words, unlike angular isokinetic dynamometers where the angle and angular velocities operate similarly for different individual statures namely same RoM and velocity irrespective if one is short or tall, this is not the case when prescribing a linear velocity of testing or training. This aspect is therefore attributed a specific accord, using a model and experimental findings.
Another section of the paper looks at some 40 papers that related to multiple-joint isokinetic dynamometry. In addition to a full quotation of the manuscripts, a table was used to delineate such items as the type of dynamometer used, the features of the study, and the main values derived from the study. Much effort has been invested in quoting what we believe to be most of the pertinent literature. The authors therefore believe that this review will help in shaping a more precise context of multiple-joint dynamometers while help users in the more correct application of this important branch of isokinetics.
Read the complete study of Dvir and Müller here
The paper may be purchased directly from the publisher.
More information on CON-TREX® units
Dvir Z, Müller S (2019): Multiple-Joint Isokinetic Dynamometry: A Critical Review. Journal of Strength and Conditioning Research. In press.
Paper of the Month – the initiative
The main objective of the PoM initiative is to serve as an update forum for users of isokinetic dynamometry. Recent papers, generally of the last 3 preceding months, relating to this technology and its applications will be reviewed regularly by Prof. Zeevi Dvir, who will select those that in his opinion present an important/relevant contribution to the science of isokinetic testing and conditioning. The selection will consider the novelty, scientific rigor and possible applicability of the study without any prejudice, reflecting PHYSIOMED’s commitment to the highest standards the company stands for as a world leader in isokinetic technology.
Based at the Dept. of Physical Therapy, the Sackler Faculty of Medicine, Tel Aviv University, Prof. Dvir serves also as a Non-teaching Adjunct Professor at the Biomechanics and Ergonomics Lab, School of Kinesiology and Health Studies (SKHS), Queen’s University, Canada.
Prof Dvir is an international leader in isokinetics. He is the author of the widely recognized leading title in the field “Isokinetics: Muscle Testing, Interpretation and Clinical Applications” (Churchill Livingstone, 1st ed., 1995; Elsevier 2nd ed., 2004). He is also the Editor-in-Chief of Isokinetics and Exercise Science (IOS Press, Amsterdam, Holland) since 1998, the only international journal dedicated to the science and practical aspects of this technology. Prof. Dvir has published more than 60 papers on isokinetics. He coined the terms Dynamic Control Ratio (DCR), which is also known as the functional ratio. The DCR has mostly been applied in the context of muscular balance around the knee especially with respect to ACL deficiency and reconstruction and is expressed as the ratio: Hecc/Qcon. Prof. Dvir was also the first to describe the DCE (the Difference between the high and low velocity Ecc/Con ratios) to assess submaximal effort, a core concept in medicolegal analysis of muscular weakness. A US patent he owns paved the way to a series of papers describing the utilization of Short Range of Motion isokinetic testing and conditioning.