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Fatiguing Joint Angle Does Not Influence Torque And Neuromuscular Responses Following Sustained, Isometric Forearm Flexion Tasks Anchored To Perceptual Intensity In Men, Dolores G. Ortega, Terry J. Housh, Robert W. Smith, Jocelyn E. Arnett, Tyler J. Neltner, John Paul V. Anders, Richard J. Schmidt, Glen O. Johnson

Department of Nutrition and Health Sciences: Faculty Publications

This study examined the effects of joint angle (JA) on maximal voluntary isometric contraction (MVIC) and neuromuscular responses following fatiguing tasks anchored to RPE. Nine men (mean ± SD: age = 20.7 ± 1.2 yrs) performed forearm flexion MVICs at elbow JAs of 75^o and 125^o before and after sustained, isometric forearm flexion tasks to failure at fatiguing joint angles (FJA) of 75^o and 125^o anchored to RPE = 8. The amplitude and frequency of the electromyographic and mechanomyographic signals were recorded. Neuromuscular efficiency was calculated by dividing normalized torque by normalized electromyographic amplitude. A dependent …

Fatiguing Joint Angle Does Not Influence Torque And Neuromuscular Responses Following Sustained, Isometric Forearm Flexion Tasks Anchored To Perceptual Intensity In Men, Dolores G. Ortega, Terry J. Housh, Robert Smith, Jocelyn E. Arnett, Tyler J. Neltner, John Paul V. Anders, Richard J. Schmidt, Glen O. Johnson

Department of Nutrition and Health Sciences: Faculty Publications

This study examined the effects of joint angle (JA) on maximal voluntary isometric contraction (MVIC) and neuromuscular responses following fatiguing tasks anchored to RPE. Nine men (mean ± SD: age = 20.7 ± 1.2 yrs) performed forearm flexion MVICs at elbow JAs of 75^o and 125^o before and after sustained, isometric forearm flexion tasks to failure at fatiguing joint angles (FJA) of 75^o and 125^o anchored to RPE = 8. The amplitude and frequency of the electromyographic and mechanomyographic signals were recorded. Neuromuscular efficiency was calculated by dividing normalized torque by normalized electromyographic amplitude. A dependent …

Performance Fatigability And Neuromuscular Responses Are Not Joint Angle Specific Following A Sustained Isometric Forearm Flexion Task Anchored To A High Perceptual Intensity In Women, Jocelyn E. Arnett, Robert W. Smith, Tyler J. Neltner, John Paul V. Anders, Dolores G. Ortega, Terry J. Housh, Richard J. Schmidt, Glen O. Johnson

Department of Nutrition and Health Sciences: Faculty Publications

Objectives: To examine the effects of joint angle (JA) on maximal voluntary isometric contractions (MVIC) and neuromuscular responses following a sustained, isometric forearm flexion task anchored to a rating of perceived exertion (RPE) of 8 (RPE=8). Methods: Nine women (age: 20.7±2.9 yrs; height: 168.8±7.2 cm; body mass: 66.3±6.8 kg) performed 2,3s forearm flexion MVICs at JAs of 75°, 100°, and 125° prior to and following a sustained, isometric forearm flexion task anchored to RPE=8 to task failure (torque reduced to zero) at JA100. Electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the biceps brachii. Results: The …

Time Course Of Changes In Torque And Neuromuscular Parameters During A Sustained Isometric Forearm Flexion Task To Fatigue Anchored To A Constant Rating Of Perceived Exertion, Robert W. Smith, Terry J. Housh, John Paul V. Anders, Tyler J. Neltner, Jocelyn E. Arnett, Richard Schmidt, Glen O. Johnson

Department of Nutrition and Health Sciences: Faculty Publications

Objective: This study examined the time course of changes in torque and electromyographic (EMG) and mechanomyographic (MMG) responses during a sustained isometric task anchored to a constant perception of exertion (RPE). Methods: Twelve college-aged men performed an isometric forearm flexion task to failure anchored to RPE=7 (OMNI-RES scale). The amplitude (AMP) and frequency (MPF) of the EMG and MMG signals from the biceps brachii were recorded. Repeated measures ANOVAs were used to examine differences for the normalized (%MVIC) torque and neuromuscular parameters. Results: The time to task failure (TTF) was 678.0±468.1s. Torque decreased significantly (p<0.001, η_p ²=0.774) …

Co-Activation, Estimated Anterior And Posterior Cruciate Ligament Forces, And Motor Unit Activation Strategies During The Time Course Of Fatigue, Cory M. Smith, Terry J. Housh, Ethan C. Hill, Josh L. Keller, Glen O. Johnson, Richard J. Schmidt

Department of Nutrition and Health Sciences: Faculty Publications

This study aimed to combine co-activation as well as anterior and posterior cruciate ligament force estimations with the motor unit activation strategies employed by the primary muscles that are involved in the movement at the knee joint. Fourteen male subject performed 25 maximal concentric isokinetic leg extension muscle actions at 120 s^-1. Electromyographic and mechanomyographic signals from the vastus lateralis and bicep femoris, as well as force, were used to measure co-activation, and estimated anterior and posterior ligament forces during the time course of fatigue. There were decreases in quadriceps force and increases in hamstring force during the …

Effects Of Intensity On Muscle-Specific Voluntary Electromechanical Delay And Relaxation Electromechanical Delay, Cory M. Smith, Terry J. Housh, Ethan C. Hill, Josh L. Keller, Glen O. Johnson, Richard J. Schmidt

Department of Nutrition and Health Sciences: Faculty Publications

The purposes of this study were to examine: 1) the potential muscle-specific differences in voluntary electromechanical delay (EMD) and relaxation electromechanical delay (R-EMD), and 2) the effects of intensity on EMD and R-EMD during step incremental isometric muscle actions from 10 to 100% maximal voluntary isometric contraction (MVIC). EMD and R-EMD measures were calculated from the simultaneous assessments of electromyography, mechanomyography, and force production from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) during step isometric muscle actions. There were no differences between the VL, VM, and RF for the voluntary EMD_E-M (onsets of the electromyographic …

Effects Of Fatigue And Recovery On Electromechanical Delay During Isokinetic Muscle Actions, Cory M. Smith, Terry J. Housh, Ethan C. Hill, Josh L. Keller, Glen O. Johnson, Richard J. Schmidt

Department of Nutrition and Health Sciences: Faculty Publications

Objective: To examine muscle-specific differences and the effects of fatigue and recovery on electromechanical delay (EMD) during maximal isokinetic muscle actions.

Approach: Thirteen men performed maximal isokinetic knee extension muscle actions at 60° s⁻¹, pretest, posttest, and after 5 min of recovery from 25 maximal isokinetic knee extensions. The onsets of the electromyographic, mechanomyographic, and force signals were used to identify EMD measures from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF).

Main results: There were posttest increases in all EMD measures for all muscles that returned to pretest levels after 5 …

Effect Of Sex On Torque, Recovery, Emg, And Mmg Responses To Fatigue, E.C. Hill, Terry J. Housh, C. M. Smith, Kristen C. Cochrane, N.D.M. Jenkins, Joel T. Cramer, Richard J. Schmidt, G. O. Johnson

Department of Nutrition and Health Sciences: Faculty Publications

The purpose of the present investigation was to examine the effect of sex on maximal voluntary isometric contraction (MVIC) torque and the EMG and MMG responses as a result of fatiguing, intermittent, submaximal (65% of MVIC), isometric elbow flexion muscle contractions. Methods: Eighteen men and women performed MVIC trials before (pretest), after (posttest), and 5-min after (5-min recovery) performing 50 intermittent, submaximal isometric muscle contractions. Surface electromyographic (EMG) and mechanomyographic (MMG) signals were simultaneously recorded from the biceps brachii muscle. Results: As a result of the fatiguing workbout torque decreased similarly from pretest to posttest for both the men (24.0%) …