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JOURNAL
OF
SPORTS SCIENCE &
MEDICINE
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Research
article
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A LOW-COST CONTACT SYSTEM TO ASSESS LOAD DISPLACEMENT VELOCITY IN A RESISTANCE TRAINING MACHINE |
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Bernat Buscą 
and Anna Font |
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Faculty of Psychology, Education Sciences and Sport Blanquerna - Ramon Llull University, Barcelona, Spain |
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© Journal of Sports Science and Medicine (2011) 10, 472 - 477 |
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| ABSTRACT | |||
| This study sought to determine the validity of a new system for
assessing the displacement and average velocity within machine-based resistance
training exercise using the Chronojump System. The new design is based on
a contact bar and a simple, low-cost mechanism that detects the conductivity
of electrical potentials with a precision chronograph. This system allows
coaches to assess velocity to control the strength training process. A validation
study was performed by assessing the concentric phase parameters of a leg
press exercise. Output time data from the Chronojump System in combination
with the pre-established range of movement was compared with data from a
position sensor connected to a Biopac System. A subset of 87 actions from
11 professional tennis players was recorded and, using the two methods,
average velocity and displacement variables in the same action were compared.
A t-test for dependent samples and a correlation analysis were undertaken.
The r value derived from the correlation between the Biopac System and the
contact Chronojump System was >0.94 for all measures of displacement
and velocity on all loads (p < 0.01). The Effect Size (ES) was 0.18 in
displacement and 0.14 in velocity and ranged from 0.09 to 0.31 and from
0.07 to 0.34, respectively. The magnitude of the difference between the
two methods in all parameters and the correlation values provided certain
evidence of validity of the Chronojump System to assess the average displacement
velocity of loads in a resistance training machine. Key words: Velocity, testing, strength training, speed events. |
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