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Biomechanics/Neuromuscular

(11) PERFORMANCE FATIGABILITY, PERCEIVED FATIGABILITY, AND NEUROMUSCULAR RESPONSES DURING A FATIGUING TASK ANCHORED TO A HIGH RATING OF PERCIEVED EXERTION

Saturday, July 13, 2024
10:00 AM – 11:30 AM East Coast USA Time
Location: Exhibit Hall

    Poster Presenter(s)

  • Trevor D. Roberts

    Doctoral Student
    University of Nebraska-Lincoln
    Lincoln, Nebraska, United States

    • Author(s)

  • Robert W. Smith, MS

    Doctoral Student
    University of Nebraska-Lincoln
    Lincoln, Nebraska, United States

  • Dolores G. Ortega, MS, CSCS

    Doctoral Student
    University of Nebraska-Lincoln
    Lincoln, Nebraska, United States

  • Jocelyn E. Arnett, MS, EP-C

    Doctoral Student
    University of Nebraska-Lincoln
    Lincoln, Nebraska, United States

  • TN

    Tyler Neltner

    Assistant Professor
    University of Wisconsin-Platteville
    Platteville, Wisconsin, United States

  • TH

    Terry J. Housh

    Full Professor
    University of Nebraska-Lincoln
    Lincoln, Nebraska, United States

  • RS

    Richard J. Schmidt

    Emeriti Professor
    University of Nebraska-Lincoln
    Lincoln, Nebraska, United States

  • GJ

    Glen O. Johnson

    Emeriti Professor
    University of Nebraska-Lincoln
    Lincoln, Nebraska, United States

Abstract Details: BACKGROUND: Few studies have assessed the interaction between performance fatigability (PF) and perceived fatigability during a fatiguing task anchored to a high rating of perceived exertion (RPE). In addition, assessing fatigue-induced changes in electromyographic amplitude (EMG AMP) and neuromuscular efficiency (NME) may provide insight into the motor unit activation strategies that modulate torque (TRQ) production during a fatiguing task.

Purpose: The present study examined the composite patterns of responses for TRQ, EMG AMP, and NME during a sustained, isometric forearm flexion task anchored to RPE=8, as well as the perceived factors that contributed to task termination.

Methods: Twelve men (mean±SD: age=20.9±2.2 yrs) completed forearm flexion maximal voluntary isometric contractions (MVICs) before and after a sustained, isometric forearm flexion task to failure (defined as TRQ reduced to zero) anchored to RPE=8. The EMG AMP was recorded from the biceps brachii (BB), and neuromuscular efficiency (NME) was calculated by dividing normalized TRQ by normalized EMG AMP. A post-test questionnaire (PTQ) with 10 Likert-type items was used to quantify the contributions of perceived sensations (i.e., pain and fatigue in the BB, forearm muscles [FM], and hand muscles [HM]) and psychological factors (i.e., loss of focus and motivation) to the decision to terminate the task. Motivation was divided into three subtypes: Motivation 1 [M1: gave maximal effort], Motivation 2 [M2: perceived that the task could not be accomplished], and Motivation 3 [M3: became bored]. Polynomial regressions (linear and quadratic) were used to define the composite relationships for normalized TRQ, EMG AMP, and NME versus time (every 10%) during the sustained task. Spearman’s Rank Order Correlations (SROC) were used to assess the relationships among the PTQ items, time to task failure (TTF), and PF (% decline in MVIC from pre-test to post-test).

Results: The composite patterns of responses indicated significant negative TRQ (p< 0.001, r=-0.972), EMG AMP (p=0.002, r=-0.857), and NME (p< 0.001, r=-0.974) versus time relationships throughout the fatiguing task. The mean (±SD) values for TTF and PF were 255.5 s (±166.3 s) and 23.5% (±13.7%), respectively. The SROC indicated significant (p≤0.05, rs=0.611-0.904) associations for FM fatigue vs. FM pain, FM fatigue vs. HM fatigue, FM fatigue vs. HM pain, FM pain vs. M3, FM pain vs. HM fatigue, FM pain vs. HM pain, HM fatigue vs. HM pain, and M2 vs. focus. There were no associations (p>0.05, rs=-0.419-0.547) among BB fatigue, BB pain, M1, TTF, and PF.

Conclusions: The present findings indicated that the decreases in TRQ and EMG AMP during a sustained, isometric task anchored to RPE=8 were likely due to the ability to voluntarily reduce TRQ to maintain the target RPE. In addition, the fatigue-induced decrease in NME during the task was likely due to excitation-contraction coupling failure that resulted from peripheral fatigue. Neither the perceived sensations or psychological factors were related to TTF or PF, but perceived sensations and psychological factors were interrelated. PRACTICAL APPLICATION: When performing an isometric task to failure anchored to RPE=8, individuals modulate their ability to continue the task by lowering their torque to maintain their target RPE. Furthermore, a PTQ with Likert-type items may be a simple way for practitioners to assess factors related to perceived fatigability.

Acknowledgements: None