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JOURNAL
OF
SPORTS SCIENCE &
MEDICINE
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Research
article
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THE INFLUENCE OF VELOCITY OVERSHOOT MOVEMENT ARTIFACT ON ISOKINETIC KNEE EXTENSION TESTS |
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Fabiano Peruzzo Schwartz1  ,
Martim Bottaro2, Rodrigo Souza Celes2, Lee E. Brown3 and Francisco Assis
de Oliveira Nascimento1 |
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1Department of Electrical Engineering, University of Brasilia, Brasilia, DF, Brazil, 2Department of Physical Education, University of Brasilia, Brasilia, DF, Brazil, 3Department of Kinesiology, California State University, Fullerton, CA, USA. |
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© Journal of Sports Science and Medicine (2010) 9, 140 - 146 |
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| ABSTRACT | |||
| Exercise on an isokinetic device involves three distinct movement
phases: acceleration, constant velocity, and deceleration. Inherent in these
phases are unique occurrences that may confound test data and, thereby,
test interpretation. Standard methods of data reduction like windowing and
other techniques consist of removing the acceleration and deceleration phases
in order to assure analysis under constant velocity conditions. However,
none of these techniques adequately quantify the velocity overshoot (VO)
movement artifact which is a result of the devices resistance imposed to
the limb. This study tested the influence of VO on isokinetic data interpretation.
A computational algorithm was developed to accurately identify each movement
phase and to delineate the VO segment. Therefore, the VO was then treated
as a fourth and independent phase. A total of sixteen healthy men (26.8
± 4.7 yrs, 1.76 ± 0.05 m, and 79.2 ± 9.4 kg) performed two sets of ten maximal
concentric extension repetitions of their dominant knee (at 60º·s-1 and
180º·s-1), on separate days and in a counterbalanced order, on a Biodex
System 3 Pro dynamometer. All the phases of the isokinetic exercise were
measured in terms of their biomechanical descriptors and according to the
developed algorithm, the windowing method, and a data reduction technique
that eliminates the first and last 10º of the total range of motion. Results
showed significant differences (p < 0.05) between the constant velocity
phases found by each method: the largest segment was obtained with the windowing
method; the second one, with the algorithm; and the smallest, with data
reduction technique. The point of peak torque was not affected by none of
the techniques, but significant differences (p < 0.05) were found between
the data including and not including the VO phase, concerning total work,
time interval, and average length of load range: VO represents more than
10% of the amount calculated in constant velocity phase. As a consequence,
the correct removal of VO was suggested as a required procedure to adequately
interpret isokinetic tests. Therefore, the use of the proposed algorithm
is advisable in order to perform analysis according to the isokinetic definition. Key words: biomechanics, dynamometry, constant velocity, phases of movement. |
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