Different derivatives of the peak moment indicate significant association between strength and function in elderly individuals.
Prof. Dvir's Commentary:
For the 2nd Paper of the Month I chose to include two papers, one from the US and one from Brazil, both dealing with motor functional issues in elderly individuals, using isokinetically derived parameters of muscle strength. Significantly, both papers relate to the concept of muscle quality (MQ), in elderly cohorts, and are hence to an extent, complementary.
Although the study of MQ is a fast growing field, a unified definition and standardization, of what is exactly MQ, has not been reached yet as pointed out by a recent review (Correa-de-Araujo et al., Frontiers in Physiology 8(87), 2017). However, one of the most significant markers of MQ is strength. But strength itself is not unequivocally defined: strength depends on the way it is being measured. Significantly, isometric strength is different from isokinetic strength while concentric isokinetic strength is different from eccentric isokinetic strength, even while leaving out the speed at which these types of strength (concentric or eccentric) are tested.
In the paper by Straight et al, MQ was defined by as the isokinetic concentric peak moment (PMC) of the knee extensors at 60°/s, divided by the by upper-leg lean mass (measured using dual-energy X-ray absorptiometry) and expressed by the unit Nm/kg. On the other hand, in the paper by Gadelha et al, MQ was defined by the isometric PM (PMI) at 60° of knee flexion (measured by an isokinetic dynamometer) divided by the thickness of the knee extensors (measured by ultrasonography) and expressed by the unit Nm/mm.
Thus, two differently isokinetically derived parameters served for assessing MQ. Interestingly, neither of the authors elaborated at depth on the reason for their parameter of choice. Furthermore, there was no attempt to compare which of the two might be more effective in terms of its explanatory power of, or its association with, the issues at hand. However, as clearly emerging from the papers, both parameters bear a strong relationship to the main issues of study, be it either the changes in lower extremity physical function in overweight or obese older women (Straight et al) or the incidence of falls in older community dwelling women (Gadelha et al). This finding serves also to support even further the decisive value and validity of using isokinetics for the specific applications described in this line of research.
Straight CR, Berg AC, Reed RA, Johnson MA, Evans EM. Reduced body weight or increased muscle quality: Which is more important for improving physical function following exercise and weight loss in overweight and obese older women? Experimental Gerontology, 108:159-165, 2018.
Gadelha AB, Neri SGR, Bottaro M, Lima RM. The relationship between muscle quality and incidence of falls in older community-dwelling women: An 18-month follow-up study. Experimental Gerontology, 110:241–24, 2018.
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.