Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
©Journal of Sports Science and Medicine (2018) 17, 465 - 474

Research article
Validation of A New Judo-Specific Ergometer System in Male Elite and Sub-Elite Athletes
Norman Helm1,2, Olaf Prieske2, Thomas Muehlbauer2,3, Tom Krüger2, Helmi Chaabene2, Urs Granacher2, 
Author Information
1 Olympic Testing and Training Center Brandenburg, Potsdam, Germany
2 Division of Training and Movement Sciences, University of Potsdam, Potsdam, Germany
3 Division of Movement and Training Sciences/Biomechanics of Sport, University of Duisburg-Essen, Essen, Germany

Urs Granacher
✉ University of Potsdam, Division of Training and Movement Science, Am Neuen Palais 10, Building 12, 14469 Potsdam, Germany
Publish Date
Received: 13-04-2018
Accepted: 11-07-2018
Published (online): 14-08-2018
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Our experimental approach included two studies to determine discriminative validity and test-retest reliability (study 1) as well as ecological validity (study 2) of a judo ergometer system while performing judo-specific movements. Sixteen elite (age: 23 ± 3 years) and 11 sub-elite (age: 16 ± 1 years) athletes participated in study 1 and 14 male sub-elite judo athletes participated in study 2. Discriminative validity and test-retest reliability of sport-specific parameters (mechanical work, maximal force) were assessed during pulling movements with and without tsukuri (kuzushi). Ecological validity of muscle activity was determined by performing pulling movements using the ergometer without tsukuri and during the same movements against an opponent. In both conditions, electromyographic activity of trunk (e.g., m. erector spinae) and upper limb muscles (e.g., m. biceps brachii) were assessed separately for the lifting and pulling arm. Elite athletes showed mostly better mechanical work, maximal force, and power (0.12 ≤ d ≤ 1.80) compared with sub-elite athletes. The receiver operating characteristic analysis revealed acceptable validity of the JERGo© system to discriminate athletes of different performance levels predominantly during kuzushi without tsukuri (area under the curve = 0.27-0.90). Moreover, small-to-medium discriminative validity was found to detect meaningful performance changes for mechanical work and maximal force. The JERGo© system showed small-to-high relative (ICC = 0.37-0.92) and absolute reliability (SEM = 10.8-18.8%). Finally, our analyses revealed acceptable correlations (r = 0.41-0.88) between muscle activity during kuzushi performed with the JERGo© system compared with a judo opponent. Our findings indicate that the JERGo© system is a valid and reliable test instrument for the assessment and training of judo-specific pulling kinetics particularly during kuzushi movement without tsukuri.

Key words: Judo-specific pulling movement, work, force, muscle activity, reliability

           Key Points
  • The judo-specific ergometer system (JERG©) is able to detect judo-specific pulling kinetics and force displacement characteristics for the lifting and pulling arm during judo-specific movements.
  • The individual adjustment of the JERG© system (i.e., height of lifting arm, pulling arm, brake resistance) is interlocked by athletes’ weight category and body height as well as the preferred judo technique.
  • The JERG© system is a valid and reliable test instrument for assessment and training of judo-specific pulling kinetics.
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