Mental Fatigue, Attentional Focus, and Countermovement Jump Performance

August 19, 2026 updated by: Oğuzhan Bozkurt, Inonu University

The Effects of Acute Mental Fatigue and Attentional Focus Instructions on Countermovement Jump Performance

This study examines whether short-term mental fatigue and different jump instructions affect how high people can jump. Thirty-two physically active university students will complete two testing sessions in random order: one after a 30-minute mentally tiring computer task and one after a 30-minute relaxing video. In both sessions, participants will perform vertical jumps while receiving one of three types of instructions: no special instruction, focusing on their own body movements, or focusing on pushing the ground away. The study will compare jump height across these conditions to better understand how mental tiredness and coaching cues affect jumping performance, which may help coaches and athletes design better training and competition preparation.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

This study uses a sex-stratified, randomized, counterbalanced crossover design with repeated measures to examine the effects of acute mental fatigue and attentional-focus instructions on countermovement jump (CMJ) performance. Thirty-two physically active undergraduate students (16 women, 16 men), aged 18-30 years, will be enrolled from the Faculty of Sport Sciences at İnönü University, Malatya, Türkiye.

Each participant will complete two experimental protocols, separated by at least 72 hours: a control protocol (approximately 30 minutes of passive viewing of a narration-free nature video) and a mental-fatigue protocol (a 30-minute computerized color-word Stroop interference task). Protocol order will be randomized and stratified by sex. In both protocols, participants will perform CMJs under three attentional-focus conditions, presented in a randomized order that is held constant within each participant across sessions: no prescribed focus, internal focus (attention directed to the participant's own body movements), and external focus (attention directed to the effect of movement on the environment). CMJ height will be recorded in centimeters using a validated video-based jump-analysis application (My Jump Lab) on a tablet camera recording at 240 frames per second, with the higher of two valid trials retained as the primary outcome for each protocol-by-focus condition.

Subjective mental fatigue will be assessed immediately before and after each protocol using a 0-10 visual analogue scale to confirm the effectiveness of the fatigue manipulation. Stroop task performance (total trials, accuracy) and adherence to the assigned attentional-focus instructions will be recorded as secondary measures.

The primary analysis will use a 2 (protocol: control, mental fatigue) x 3 (focus: no prescribed, internal, external) x 2 (sex: women, men) mixed-model ANOVA on CMJ height, with protocol and focus as within-participant factors and sex as a between-participant factor. Reporting will follow CONSORT 2025 and the CONSORT extension for randomized crossover trials.

Study Type

Interventional

Enrollment (Estimated)

32

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Turkey (Türkiye)
      • Malatya, Turkey (Türkiye), 44280
        • İnönü University, Faculty of Sport Sciences
        • Contact:
        • Principal Investigator:
          • Oguzhan BOZKURT, PhD

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Age 18-30 years
  • Third- or fourth-year undergraduate student in the Faculty of Sport Sciences, İnönü University
  • Engaged in structured physical activity on at least 2 days per week
  • Normal or corrected-to-normal vision and normal color vision
  • Able to safely perform maximal vertical jumps

Exclusion Criteria:

  • Major lower-extremity surgery or injury
  • Musculoskeletal injury during the preceding 6 months that could affect jumping
  • Diagnosed neurological, psychiatric, or cardiovascular disorder
  • Regular use of medication that could influence alertness, fatigue, cardiovascular responses, or neuromuscular performance
  • Any health condition compromising safety or measurement validity

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Control-First Sequence
Participants complete the control protocol (30-min passive nature-video viewing) in the first session and the mental-fatigue protocol (30-min Stroop task) in the second session, separated by at least 72 hours. In both sessions, participants perform countermovement jumps under three attentional-focus conditions (no prescribed focus, internal focus, external focus) in a randomized, participant-fixed order.
Behavioral: Control Protocol (Nature Video)
Approximately 30 minutes of passive viewing of a narration-free nature video under standardized lighting, seating, and sound conditions, serving as the non-fatiguing control condition matched in duration to the mental-fatigue protocol.
Behavioral: No Prescribed Focus Instruction
A verbal cue delivered before each jump attempt with no directional attentional instruction: "When you are ready, jump as high as possible."
Behavioral: Internal Focus Instruction
A verbal cue delivered before each jump attempt directing attention to the participant's own body movements: "When you are ready, focus on extending your knees and hips as quickly and explosively as possible while jumping as high as possible."
Behavioral: External Focus Instruction
A verbal cue delivered before each jump attempt directing attention to the effect of movement on the environment: "When you are ready, focus on pushing the ground away from you as quickly and explosively as possible while jumping as high as possible."
Experimental: Mental-Fatigue-First Sequence
Participants complete the mental-fatigue protocol (30-min Stroop task) in the first session and the control protocol (30-min passive nature-video viewing) in the second session, separated by at least 72 hours. In both sessions, participants perform countermovement jumps under three attentional-focus conditions (no prescribed focus, internal focus, external focus) in a randomized, participant-fixed order.
Behavioral: No Prescribed Focus Instruction
A verbal cue delivered before each jump attempt with no directional attentional instruction: "When you are ready, jump as high as possible."
Behavioral: Internal Focus Instruction
A verbal cue delivered before each jump attempt directing attention to the participant's own body movements: "When you are ready, focus on extending your knees and hips as quickly and explosively as possible while jumping as high as possible."
Behavioral: External Focus Instruction
A verbal cue delivered before each jump attempt directing attention to the effect of movement on the environment: "When you are ready, focus on pushing the ground away from you as quickly and explosively as possible while jumping as high as possible."
Behavioral: Mental-Fatigue Protocol (Stroop Task)
A 30-minute computerized color-word Stroop interference task delivered as one uninterrupted block on a custom program, in which participants identify the font color of color-word stimuli while ignoring word meaning, inducing acute mental fatigue prior to countermovement jump testing.
Other Names:
  • Color-Word Stroop Task

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Countermovement Jump Height
Time Frame: Assessed once per attentional-focus condition (higher of two valid trials) approximately 30 seconds after completion of each 30-minute protocol (control or mental fatigue), across two sessions separated by at least 72 hours.
Vertical jump height, measured in centimeters, recorded using a validated video-based jump-analysis application (My Jump Lab) at 240 frames per second. The higher of two valid trials in each protocol-by-attentional-focus condition (control vs. mental fatigue x no prescribed focus, internal focus, external focus) will be retained as the outcome value for that condition.
Assessed once per attentional-focus condition (higher of two valid trials) approximately 30 seconds after completion of each 30-minute protocol (control or mental fatigue), across two sessions separated by at least 72 hours.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Subjective Mental Fatigue Rating
Time Frame: Immediately before and immediately after each 30-minute protocol (control and mental fatigue), across two experimental sessions separated by at least 72 hours.
Self-reported mental fatigue rated on a 0-10 visual analogue scale, in response to "How mentally fatigued do you feel right now?" (0 = not mentally fatigued at all, 10 = the highest possible level of mental fatigue).
Immediately before and immediately after each 30-minute protocol (control and mental fatigue), across two experimental sessions separated by at least 72 hours.
Stroop Task Performance
Time Frame: Continuously recorded throughout the 30-minute mental-fatigue protocol, administered in one of the two experimental sessions per participant (protocol order randomized).
Total trials completed, number of correct and incorrect responses, and accuracy (%), recorded automatically by the Stroop task software during the mental-fatigue protocol.
Continuously recorded throughout the 30-minute mental-fatigue protocol, administered in one of the two experimental sessions per participant (protocol order randomized).
Focus-Instruction Adherence
Time Frame: Assessed once per attentional-focus condition, immediately after completion of each 30-minute protocol (control or mental fatigue), across two experimental sessions separated by at least 72 hours.
Self-reported adherence to the assigned attentional-focus instructions, rated on a 0-10 visual analogue scale.
Assessed once per attentional-focus condition, immediately after completion of each 30-minute protocol (control or mental fatigue), across two experimental sessions separated by at least 72 hours.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Inonu University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

September 1, 2026

Primary Completion (Estimated)

October 1, 2026

Study Completion (Estimated)

November 1, 2026

Study Registration Dates

First Submitted

August 17, 2026

First Submitted That Met QC Criteria

August 19, 2026

First Posted (Actual)

August 21, 2026

Study Record Updates

Last Update Posted (Actual)

August 21, 2026

Last Update Submitted That Met QC Criteria

August 19, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • INU-2026-10953
  • 2026/10953 (Other Identifier: Inonu University Scientific Research Ethics Committee for Health Sciences)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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