Acute Mental Fatigue and Muscle Strength
Influence of Acute Mental Fatigue on Muscle Strength and Limb Symmetry in Healthy Adults
This study will investigate the acute effects of mental fatigue on lower-extremity muscle strength and limb symmetry in healthy young adults. Participants will complete lower-extremity strength testing before and after a standardized computer-based mental fatigue protocol involving tasks of attention, reaction time, concentration, and working memory. Muscle strength and limb symmetry will be assessed using isokinetic dynamometry, with muscle activity measured using surface electromyography. Participants will also complete subjective measures of mental fatigue, sleepiness, mental effort, and perceived physical exertion. Heart rate will be monitored throughout the study, and brain activity may be assessed during cognitive tasks. The study will determine whether acute mental fatigue is associated with changes in muscle strength, limb symmetry, and neuromuscular performance.
Study Overview
Status
Conditions
Intervention / Treatment
Detailed Description
This study will investigate the acute effects of mental fatigue on lower-extremity muscle strength, interlimb symmetry, and neuromuscular performance in healthy young adults. The study will use a within-subject, repeated-measures design in which participants complete lower-extremity strength testing immediately before and after a standardized computer-based mental fatigue protocol. Each participant's pre-fatigue measurements will serve as the baseline comparison for their post-fatigue measurements.
Participants will complete one experimental session lasting up to approximately two hours at the Florida Institute for Human and Machine Cognition (IHMC) Healthspan, Resilience, and Performance Research Complex. Before testing, participants will undergo eligibility screening, provide written informed consent, and complete familiarization with the strength-testing procedures and computer-based cognitive tasks. Following familiarization, participants will complete a standardized rest period of at least five minutes before baseline measurements are collected.
Lower-extremity muscle strength will be assessed using a Biodex isokinetic dynamometer. Participants will perform knee extension and flexion with both lower extremities at three different movement speeds to assess strength across multiple testing conditions. Peak torque will be used as a primary measure of muscle strength. Testing of both limbs will also allow calculation of a Limb Symmetry Index (LSI) to quantify differences in strength between the lower extremities. Participants will rate their perceived physical exertion following each strength assessment.
Surface electromyography (EMG) will be used to record muscle activity from selected muscles of both thighs during strength testing. Participants may also perform maximal voluntary isometric contractions before the primary strength assessment to assist with normalization and interpretation of EMG signals. EMG measurements will be used to examine whether changes in strength following the mental fatigue protocol are accompanied by changes in muscle activity.
Following the baseline strength assessment, participants will complete approximately 30 minutes of standardized computer-based cognitive tasks designed to require sustained attention, concentration, reaction time, working memory, and mental effort and thereby induce acute mental fatigue. Tasks may include a psychomotor vigilance task, an incongruent Stroop task, and an n-back working-memory task. Reaction time and response accuracy may be recorded during the cognitive tasks.
Subjective mental fatigue and sleepiness will be assessed before and after the mental fatigue protocol. Following the cognitive tasks, participants will also rate the mental effort required to complete the tasks. These measures will be used to characterize the subjective response to the mental fatigue protocol and evaluate whether participants experienced increased mental fatigue following the intervention.
Heart rate and cardiac activity may be continuously monitored using a Polar H10 chest sensor during the experimental session to provide additional information regarding physiological responses during the strength-testing and cognitive-task portions of the protocol. Brain electrical activity may also be recorded using noninvasive electroencephalography (EEG) during the cognitive tasks in a subset of participants.
Immediately following completion of the mental fatigue protocol and post-task questionnaires, participants will repeat the same bilateral Biodex strength assessment performed at baseline. Testing procedures, positioning, movement speeds, instructions, and outcome measurements will be kept consistent between the pre- and post-fatigue assessments. Surface EMG will again be recorded during strength testing, and participants will rate their perceived physical exertion.
The primary analyses will compare pre- and post-fatigue measures of lower-extremity muscle strength and limb symmetry to determine whether acute mental fatigue is associated with changes in peak torque or LSI. Additional analyses will examine subjective mental fatigue, sleepiness, mental effort, perceived physical exertion, muscle activity, cognitive-task performance, and physiological responses. The findings will help determine whether acute mental fatigue should be considered when measuring and interpreting lower-extremity strength and limb symmetry in research, rehabilitation, and human performance settings.
Study Type
Enrollment (Estimated)
Phase
- Not Applicable
Contacts and Locations
Study Contact
- Name: Nicole K Rendos, PhD
- Phone Number: 850-202-4442
- Email: nrendos@ihmc.org
Study Locations
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Florida
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Pensacola, Florida, United States, 32502
- Recruiting
- Florida Institute for Human and Machine Cognition
-
Contact:
- Nicole Rendos, PhD
- Phone Number: 850-202-4442
- Email: nrendos@ihmc.org
-
-
Participation Criteria
Eligibility Criteria
Ages Eligible for Study
Accepts Healthy Volunteers
Genders Eligible for Study
Description
Inclusion Criteria:
- Age 18-39 years
- Able to produce maximal force against Biodex protocol
- Able to perform required lower extremity movements through range of motion necessary for Biodex protocol
- No known cognitive impairment
- Sufficient musculoskeletal health to complete the tasks
Exclusion Criteria:
- History of a neurological disorder, disease, or cognitive impairment that may affect cognition, motor control, reaction time, or force production
- History of musculoskeletal injury affecting the lower extremities within the past 6 months
- History of lower extremity surgery affecting force production of the hip, knee, or ankle
- Color-vision impairment
- Significant visual or hearing impairment
- History of migraine headaches
- Current significant sleep disturbances or sleep deprivation
- Head injury that may affect cognitive function
- Medical condition affecting ability to produce maximal force safely
- Allergy to adhesive tape, parabens, or propylene glycol
- Scalp lacerations, open wounds, or sutures on the scalp
- Cranial surgery or skull defects
- History of unexplained dizziness or fainting in the past 6 months
- Individuals who are pregnant, prisoners, or not yet adults
- Inability to communicate with investigators
- Inability to provide written informed consent
Study Plan
How is the study designed?
Design Details
- Primary Purpose: Basic Science
- Allocation: N/A
- Interventional Model: Single Group Assignment
- Masking: None (Open Label)
Arms and Interventions
Participant Group / Arm |
Intervention / Treatment |
|---|---|
|
Experimental: Mental Fatigue Intervention
Participants will complete baseline lower-extremity muscle strength testing followed by approximately 30 minutes of standardized computer-based cognitive tasks designed to induce acute mental fatigue. Lower-extremity muscle strength testing will then be repeated immediately following the mental fatigue intervention. |
Participants will complete approximately 30 minutes of standardized computer-based cognitive tasks designed to induce acute mental fatigue. The tasks require sustained attention, concentration, reaction time, working memory, and mental effort and may include the Psychomotor Vigilance Task (PVT), incongruent Stroop task, and n-back task. Participants will complete the mental fatigue protocol after baseline strength testing and before the post-intervention strength assessment. Subjective mental fatigue and sleepiness will be assessed before and after the intervention, and perceived mental effort will be assessed following the intervention. |
What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Lower-Extremity Muscle Strength
Time Frame: Baseline and immediately following the approximately 30-minute mental fatigue intervention, during a single study visit lasting up to 2 hours.
|
Lower-extremity muscle strength will be assessed using a Biodex isokinetic dynamometer during bilateral knee extension and flexion at three different movement speeds. Peak torque will be recorded as the primary measure of muscle strength. Changes in peak torque from baseline to immediately following the computer-based mental fatigue intervention will be evaluated. |
Baseline and immediately following the approximately 30-minute mental fatigue intervention, during a single study visit lasting up to 2 hours.
|
|
Lower-Extremity Limb Symmetry
Time Frame: Baseline and immediately following the approximately 30-minute mental fatigue intervention, during a single study visit lasting up to 2 hours.
|
Limb symmetry will be assessed using peak torque measurements obtained from both lower extremities during isokinetic knee extension and flexion testing. A Limb Symmetry Index (LSI) will be calculated to quantify the similarity in muscle strength between the two lower extremities. Changes in LSI from baseline to immediately following the computer-based mental fatigue intervention will be evaluated. |
Baseline and immediately following the approximately 30-minute mental fatigue intervention, during a single study visit lasting up to 2 hours.
|
Collaborators and Investigators
Investigators
- Principal Investigator: Nicole K Rendos, PhD, Florida Institute for Human and Machine Cognition
Study record dates
Study Major Dates
Study Start (Actual)
Primary Completion (Estimated)
Study Completion (Estimated)
Study Registration Dates
First Submitted
First Submitted That Met QC Criteria
First Posted (Actual)
Study Record Updates
Last Update Posted (Actual)
Last Update Submitted That Met QC Criteria
Last Verified
More Information
Terms related to this study
Additional Relevant MeSH Terms
Other Study ID Numbers
- IRB-2026-0026
Plan for Individual participant data (IPD)
Plan to Share Individual Participant Data (IPD)?
IPD Plan Description
De-identified individual participant data that underlie the results reported in publications from this study may be made available to other researchers for scientific research purposes. Data will be shared without information that directly identifies participants.
IPD Sharing Time Frame
Data will be available beginning 12 months and ending 36 months following publication of the primary findings from this study.
IPD Sharing Access Criteria
De-identified data may be shared with scientific and clinical researchers for research purposes, including individual participant data meta-analyses. Requests for data should be directed to Dr. Nicole Rendos at nrendos@ihmc.org and may be submitted up to 36 months following publication of the primary findings from this study. Researchers requesting access will be required to provide an appropriate scientific rationale for the request and sign a data access agreement before receiving the data.
IPD Sharing Supporting Information Type
- STUDY_PROTOCOL
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
Studies a U.S. FDA-regulated device product
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