Development Of a New Motorized Isometric Dynamometer For Measuring Elbow Flexor Muscle Strengths Characteristics

Introduction
Evaluation of elbow flexor muscle strength’s characteristics is an important scientific tool in sport injuries management.
The aim of this study was to develop a new apparatus capable of accurately measuring isometric peak torque, rate of
torque development, time to peak torque, impulse and reflex time in the full range of motion. Additionally there was a
need of working also in eccentric and concentric mode in order to be capable for use in studies related to exerciseinduced
muscle damage.

Methods
The new dynamometer (figure 1) consists of a modified bed, a dynamometric unit, an electronic unit and a computer
with the related software installed. The main dynamometric unit’s parts are a dc motor, a gear reducer, a lever arm and
three sensors for torque, angle and velocity. The bidirectional communication via serial port between the computer and
the electronic unit results in appropriate motor functioning on the one hand and in real time data acquisition on the other
hand.
To establish the reliability of the new testing apparatus and determine possible sources of errors in the results, a series
of validity and reproducibility tests (test-retest correlations within day and between two days) was undertaken while
comparisons were made with measurements obtained from Cybex 6000.

Results
The strength of the linear relationships between measurements in validity tests was analyzed using a coefficient of
determination (r2), while Intraclass Correlation Coefficient (ICC[2,1]) was calculated to estimate the reproducibility of
measurements. The statistical outcomes of the validity tests showed high linearity (r2>0.99) for both torque and angle
measurements. The coefficient of determination (r2) was also calculated for comparison with the measurements
obtained by Cybex 6000 and its value was 0,9784. The ICC[2,1] (between days) for peak isometric torque in 90 degrees
was 0,9879. The respective Standard Error of Measurement (SEM) was 1,7982Nm. The above values show high
reproducibility.

Discussion / Conclusions
Our results indicate that the isometric evaluation of elbow flexor muscle characteristics with the new dynamometer is
accurate and reproducible between days. Thus, the new testing apparatus appears to have the capability of being a very
useful instrument in studies related to sports sciences.

References
[1]. Hopkins W. (2000). Sports Med, 30(1), 1-15
[2]. Denegar C. & Ball D. (1993). J Sport Rehab, 2, 35-42
[3]. Clarkson P. & Nosaka K. (1992). Med Sci Sports Exerc, 24(5), 512-520

NOTA: O texto com a iconografia está no anexo

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