Scand J Med Sci Sports 2002. 12: 218 -222  COPYRIGHT © BLACKWELL MUNKSGAARD 2002 ISSN 0905-7188

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SCANDINAVIAN JOURNAL O F

MEDICINE & SCIENCE IN SPORTS

Reliability of isokinetic supine bench press in healthy women using the Ariel Computerized Exercise System

W. J. A. Grooten', V. Puttemans2, R. J. M. Larsson"3

'Karolinska Institutet, Department of Physical Therapy, Stockholm Sweden, Department of Kinesiology, KU, 3Leuven, Belgium. Orebro Physical Therapy, Sweden

Corresponding author: WJA Grooten, Neurotec Department, Division of Physical Therapy, Karolinska Institutet, 23100; S-141 83 HUDDINGE, Sweden. Tel. +46-8-585-83911, Fax: +46-8-585-83905, E-mail: wim.grooten@gym.ki.se

Accepted for publication 21 February 2002

The aim of this study was to assess reliability of the Ariel Computerized Exercise System (ACES) `multifunction exerciser'. Twenty-three healthy women completed three sets, three repetitions each, of maximal isokinetic supine bench press at two different velocities, slow (10/s) and moderate (25/s). The following performance parameters were studied: peak and average force, peak and average power, and total

work. The experiment was repeated for two days. Intraclass correlation coefficients (ICC12,11) varied between 0.947 and 0.755 at 10'/s and between 0.861 and 0.654 at 25'/s. The standard error of the measurement (SEM), the smallest detectable difference (SDD), and the coefficient of variation (CV) indicated that it is possible to achieve reliable and clinically relevant measurements with the ACES.

In physical therapy, there is a great need for reliable functional evaluation tools to show the effects of rehabilitation or training programs. A common treatment outcome parameter is `muscular strength.' The operationalization of the concept of strength is usually `peak torque', but with current computerized isokinetic exercise systems, other performance parameters are obtainable as well. These parameters, such as `average force', `maximal and average power', or `total work', may describe the physiological changes in muscular performance resulting from rehabilitation in a better way (Abernathy, Wilson, Logan, 1995). Isokinetic testing is clinically accepted worldwide due to the possibility of measuring the maximal muscular performance of subjects over the total range of motion (ROM) and due to the reliability of the technique (Abernethy, Wilson, Logan, 1995; Bandy & McLaughlin, 1993; Dvir, 1991). However, isokinetics is not a functional way of testing, and the reliability of combined body movements like isokinetic supine bench press and the use of parameters other than peak torque have not been studied properly. A good way to describe the functional capacity of a patient or athlete is to test the muscular performance in a combined body motion (closed chain situation), where information about the strength and co-ordination of several muscles around several joints is obtained at the same time. The Ariel Computerized Exercise System (ACES) `multifunction exerciser' is a

hydraulic measurement and exercise system that evaluates the muscular performance in combined body motions like supine bench press or upright squat. A microcomputer controls a stepper motor that gives balanced resistance to make the movement isokinetic (constant velocity of the resistance arm through the ROM to a max of over 1000'/s). One study tested the relative reliability of the ACES 'multifunction exerciser' in supine bench press, presenting correlation coefficients in healthy male subjects; and one study was made of the reproducibility and validity of the ACES (Hortobagyi & Katch, 1990; Jacobs & Pope, 1986). Beyond these studies, the need remains to make a generalization to female subjects and to study the absolute reliability of measurements. Moreover, the validity of the device is unclear because the ACES does not correct for the gravitational moments of forces, e.g., resistance arm weight and segment weights (Gleeson & Mercer, 1996). The ACES is constructed so that the weight of the resistance arm is counterbalanced.

The concept of reliability concerns the stability and reproducibility of measurements between different applications of a test. Rothstein defines reliability as "the consistency of a measurement when all conditions are thought to be held constant" (Rothstein, 1985). Due to the number of statistical methods available for calculating the reliability of muscle force measurements in

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