Torque-onset determination: Unintended consequences of the threshold method |
| |
Affiliation: | 1. Laboratory of Biomechanics of Human Movement, Dept. Physical Therapy, Speech and Occupational Therapy, School of Medicine, University of Sao Paulo, Sao Paulo, Brazil;2. SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark |
| |
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-N m- and relative 5%MVC-thresholds. Results: The 5%MVC TOD-biases were similar for boys and men, but the corresponding 4-N m-based biases were markedly different (40.3 ± 14.1 vs. 18.4 ± 7.1 ms, respectively; p < 0.001). Boys–men EMD differences were most affected, increasing from 5.0 ms (visual) to 26.9 ms (4 N m; p < 0.01). Men’s visually-based torque kinetics tended to be faster than the boys’ (NS), but the 4-N m-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. |
| |
Keywords: | EMD RTD RFD Torque kinetics Onset bias Children ANOVA" },{" #name" :" keyword" ," $" :{" id" :" k0040" }," $$" :[{" #name" :" text" ," _" :" analysis of variance EMG" },{" #name" :" keyword" ," $" :{" id" :" k0050" }," $$" :[{" #name" :" text" ," _" :" electromyography EMD" },{" #name" :" keyword" ," $" :{" id" :" k0060" }," $$" :[{" #name" :" text" ," _" :" electro-mechanical delay HSD" },{" #name" :" keyword" ," $" :{" id" :" k0070" }," $$" :[{" #name" :" text" ," _" :" honest significant difference MVC" },{" #name" :" keyword" ," $" :{" id" :" k0080" }," $$" :[{" #name" :" text" ," _" :" maximal voluntary contraction RFD" },{" #name" :" keyword" ," $" :{" id" :" k0090" }," $$" :[{" #name" :" text" ," _" :" rate of force development RTD" },{" #name" :" keyword" ," $" :{" id" :" k0100" }," $$" :[{" #name" :" text" ," _" :" rate of torque development peak rate of torque development TOD" },{" #name" :" keyword" ," $" :{" id" :" k0120" }," $$" :[{" #name" :" text" ," _" :" torque-onset determination Tq" },{" #name" :" keyword" ," $" :{" id" :" k0130" }," $$" :[{" #name" :" text" ," _" :" torque tRTD" },{" #name" :" keyword" ," $" :{" id" :" k0140" }," $$" :[{" #name" :" text" ," _" :" time to peak rate of torque development |
本文献已被 ScienceDirect 等数据库收录! |
|