Mental Fatigue and the High Cost of Ignoring the Brain in Sports Performance
- Joseph Lucas
- Jul 11
- 4 min read
Updated: Jul 11
Introduction
In the world of elite athletic performance, strength, endurance, and skill often dominate the conversation. But one factor continues to be overlooked mental fatigue (MF). Emerging evidence confirms that the brain is not just a bystander in athletic performance; it’s a critical driver. This detailed review explores the groundbreaking findings from Staiano et al. (2023), which reveal how cognitive load impairs physical performance and how athletes can counteract these effects through targeted cognitive performance training.
What Is Mental Fatigue?
Mental fatigue is defined as a psychobiological state resulting from prolonged or demanding cognitive activity. It is characterized by a subjective feeling of tiredness and reduced cognitive function, even when physiological markers such as heart rate and blood lactate remain unchanged.
In elite sports, this mental fatigue can be triggered not only by formal cognitive tasks but also by pre-game tactical meetings, film review sessions, use of digital devices, social interactions, and stressors associated with competition. The body may feel fresh, but the mind is taxed and that has direct consequences on performance.
The Study: Method and Design
The research conducted by Staiano et al. used a two-part randomized, within-subject crossover design to measure the effects of mental fatigue on performance. Sixteen trained participants completed:
Part 1: Cognitive tasks followed by isolated weightlifting tests.
Part 2: Cognitive tasks intermixed with a resistance training session, followed by a 20-minute cycling time trial.
In both parts of the study, participants experienced either a mental fatigue (MF) condition or a control condition, with pre- and post-session cognitive, perceptual, and physiological data collected.
Key assessments included:
Rating of Perceived Exertion (RPE)
Brunel Mood Scale (BRUMS)
Mental Fatigue Visual Analog Scale (MF-VAS)
Psychomotor Vigilance Test (PVT)
Electromyography (EMG)
Blood Lactate & Heart Rate Monitoring
Key Findings
1. Mental Fatigue Increases Perceived Exertion (RPE)
Under the mental fatigue condition, participants rated lifting tasks as more difficult even when the actual weight and physiological effort remained constant. This increase in RPE was observed across all weight intensities (20%–80% of 1RM).
Athletes in the MF group perceived the same weight as 7% to 15% heavier than in the control group.
2. Endurance Performance Declines Under Mental Fatigue
In the 20-minute time trial following mentally fatiguing tasks, performance dropped significantly:
5% decrease in total distance cycled
Reduced average power output
No significant changes in heart rate or lactate suggesting the decline was due to central (brain-based) mechanisms, not physical limitations.
3. Mental Fatigue Reduces Cognitive Readiness and Alertness
Performance on the Psychomotor Vigilance Test (reaction time and lapses) declined significantly post-MF compared to the control condition, indicating impaired focus, slower reaction times, and reduced mental readiness.
4. Mood State and Cognitive Load Matter
Mental fatigue increased anger, fatigue, and boredom, while reducing vigor. Athletes under the MF condition also experienced higher mental demand, frustration, and effort, according to the NASA Task Load Index.
Practical Implications for Athletes and Coaches
1. Mental Fatigue Occurs Outside of Training
Cognitive fatigue doesn’t only result from formal cognitive drills. It can accumulate from common pre- and intra-training behaviors:
Scrolling on smartphones during rest periods
Tactical briefings before training
Stress from academics, personal life, or competition pressure
These sources of MF can compromise session quality without athletes even realizing it.
2. RPE Is Influenced by Mental State, Not Just Physical Load
Traditional training load monitoring may underestimate total athlete load if mental fatigue is not accounted for. Two athletes lifting the same weight may report drastically different levels of effort based on their cognitive state.
3. Athletes Must Train Cognitive Resilience
Incorporating Brain Endurance Training (BET) or structured neurocognitive training can build resilience to MF. These methods aim to train the same prefrontal brain regions responsible for managing effort perception, focus, and fatigue.
BET has shown promise in enhancing physical and multitasking performance by conditioning athletes to perform under cognitive load just like in competition.
4. Smartphone Use and Multitasking Must Be Monitored
Studies show that smartphone use prior to training decreases volume-load in resistance workouts. Coaches and athletes should consider digital “off zones” during warm-ups and between sets to avoid cognitive overload.
Strategic Recommendations
Implement Cognitive Load Monitoring Include cognitive fatigue check-ins (e.g., MF-VAS, PVT) in weekly readiness assessments alongside HRV and workload data.
Use Cognitive Warm-Ups Carefully Avoid complex or stimulating activities before key lifts or conditioning sessions. Replace them with grounding routines to sharpen focus.
Add Brain Endurance Training Introduce cognitive tasks that simulate game-like decision-making under fatigue, either as standalone sessions or integrated into physical drills.
Educate Athletes on the Brain-Body Link Build athlete buy-in by explaining how brain function affects their lifts, conditioning, and in-game execution.
Final Thoughts
This study confirms what elite coaches and performance professionals are beginning to understand: Cognitive fatigue is a limiting factor in physical performance. Athletes who manage and train their cognitive systems are not just tougher mentally they're physically more efficient, enduring, and competitive.
Cognitive performance training is not a trend. It is the next frontier of elite athletic development. And those who embrace it early will gain a measurable edge..
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