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Torque-onset determination: Unintended consequences of the threshold method.

Dotan, R and Jenkins, G and O'Brien, TD and Hansen, S and Falk, B (2016) Torque-onset determination: Unintended consequences of the threshold method. Journal of Electromyography and Kinesiology, 31. pp. 7-13. ISSN 1050-6411

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Abstract

BACKGROUND: Compared with visual torque-onset-detection (TOD), threshold-based TOD produces onset bias, which increases with lower torques or rates of torque development (RTD). PURPOSE: To compare the effects of differential TOD-bias on common contractile parameters in two torque-disparate groups. METHODS: Fifteen boys and 12 men performed maximal, explosive, isometric knee-extensions. Torque and EMG were recorded for each contraction. Best contractions were selected by peak torque (MVC) and peak RTD. Visual-TOD-based torque-time traces, electromechanical delays (EMD), and times to peak RTD (tRTD) were compared with corresponding data derived from fixed 4-Nm- and relative 5%MVC-thresholds. RESULTS: The 5%MVC TOD-biases were similar for boys and men, but the corresponding 4-Nm-based biases were markedly different (40.3±14.1 vs. 18.4±7.1ms, respectively; p<0.001). Boys-men EMD differences were most affected, increasing from 5.0ms (visual) to 26.9ms (4Nm; p<0.01). Men's visually-based torque kinetics tended to be faster than the boys' (NS), but the 4-Nm-based kinetics erroneously depicted the boys as being much faster to any given %MVC (p<0.001). CONCLUSIONS: When comparing contractile properties of dissimilar groups, e.g., children vs. adults, threshold-based TOD methods can misrepresent reality and lead to erroneous conclusions. Relative-thresholds (e.g., 5% MVC) still introduce error, but group-comparisons are not confounded.

Item Type: Article
Uncontrolled Keywords: 1106 Human Movement And Sports Science
Subjects: Q Science > QM Human anatomy
G Geography. Anthropology. Recreation > GV Recreation Leisure > GV561 Sports
Divisions: Sport & Exercise Sciences
Publisher: Elsevier
Related URLs:
Date Deposited: 06 Oct 2016 08:08
Last Modified: 07 Sep 2017 22:49
DOI or Identification number: 10.1016/j.jelekin.2016.08.017
URI: http://researchonline.ljmu.ac.uk/id/eprint/4255

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