Eccentric vs. concentric isokinetic training: A new study from Japan may get us closer to solving a long and complicated debate.
Prof. Dvir's Commentary:
The paper by Maeo et al was selected to appear as the first "Paper of the Month" due to its rigorous approach and high relevance to an issue that is at the heart of isokinetics, namely neuromuscular adaptation to concentric (CON) vs. eccentric (ECC) training. This issue has been investigated by a number of studies dating back to the '80s without a clear-cut conclusion. A major reason for this situation was the absence of an effective, built-in, mechanism to control and match the isokinetic CON and ECC total amount of work (TAW, in kJ) spent during the training period, which excluded a valid interpretation of the results.
In this new study, in which the knee extensors of one leg were trained eccentrically, while the same muscles of the contra-lateral leg were trained concentrically, the TAW was effectively controlled and matched-up between the training legs, using a special feature of the CON-TREX® dynamometer.
In order to follow the physiological and structural variations during the training period, the authors have employed surface electromyography (EMG) and magnetic resonance imaging (MRI), along the course of training. The protocol was formulated as follows: 10w x 2d x 6set x 10reps using a single velocity: 180 °/s. However, due to the need to match the ECC with the CON work, the number of repetitions within each set was varied as required. This eventually meant that the total number of repetitions during CON training was, on average, close to 40 % more than that required for its ECC counterpart.
The most important findings indicated that following training, the % change (%Δ) in the peak moment (PM), and EMG activation of the ECC leg were significantly greater than those recorded for the CON leg, while the %Δ in anatomical cross-sectional area and muscle volume were exclusive to the ECC-leg. Thus, holding TAW equal, it seems that it is the higher PM obtained during the medium/high-speed ECC contractions that drove muscle hypertrophy. Interestingly the %Δ EMG explained a decisive part of the total variance in the PM, particularly with regard to ECC training.
Criticism regarding the use of isokinetic dynamometry (ISD) in training relates invariably to the nonfunctional nature of the movement, the logistic limitation and the cost of the dynamometers. But in my opinion, the indications derived from this study, together with the ability to effectively and accurately control input parameters such as the RoM, velocity, TAW, and level of contraction, as well as the automation of sets, repetitions and pacing, and in addition to unrivaled documentation outweigh, by far, these limitations, rendering ISD an exclusive training tool. This is further amplified, in the case of maximal ECC training as the latter cannot, by definition, be realized using any other mechanical means, unless provided with a sufficiently strong and controllable external power source, the core of ISD.
Read the complete study here
This paper may be purchased directly from the publisher.
More information on CON-TREX® units
Maeo S, Shan X, Otsuka S, Kanehisa H, Kawakami Y. Neuromuscular Adaptations to Work-matched Maximal Eccentric versus Concentric Training. Medicine and Science in Sports and Exercise. 2018;50(8):1629-1640. doi:10.1249/MSS.0000000000001611.
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.