Mental Fatigue Can Impair Physical Performance

Summary: Partaking in mentally demanding tasks and experiencing mental fatigue can have a significant impact on your physical exercise performance, a new study reports.

Source: University of Birmingham

People subjected to mentally demanding tasks are likely to find it harder to go on to perform physical exercise, a study shows.

Researchers at the University of Birmingham’s School of Sport, Exercise and Rehabilitation Sciences, measured the effects of cognitive tasks on a group of 16 men and women to examine what happened to their perception of physical exertion. Their results showed that mental fatigued participants had an increased sense of exertion during physical exercise.

The findings, published in the International Journal of Sports Physiology and Performance, suggest that taking the effects of mental fatigue into account during training may help athletes perform better.

In the light of their findings, the researchers recommend coaches reduce athletes’ exposure to mentally challenging tasks, such as smartphone use, before and during training and competitions. Longer term, they should consider ‘brain endurance training’ to increase resilience to mental fatigue.

Lead author Dr Chris Ring said: “We know that the brain plays a part in physical performance, but the specific effects of mental fatigue have not been well understood.

“We know that athletes will often be browsing on their smartphones in rests between competing and training. All of that requires mental effort and our results strongly suggest that athletes and coaches need to better understand the effects of these activities on overall performance.”

This shows a woman running
The findings, published in the International Journal of Sports Physiology and Performance, suggests that taking the effects of mental fatigue into account during training may help athletes perform better. Image is in the public domain

During the tests, participants completed a 90-minute mental task which involved identifying letter sequences on a screen. They then completed a series of weight lifting repetitions. A control group watched neutral videos before taking part in the physical task.

In a second experiment, participants completed a series of resistance training exercises, followed by a 20-minute cycling time trial. They performed cognitive tasks before and between the exercises with a control group again watching a neutral video. After the cognitive tasks participants took an online test to confirm levels of fatigue.

In each experiment, the researchers recorded an increase in perceived exertion – how hard it felt to perform the task – among the mentally fatigued participants. In the second experiment, the researchers also noticed a reduced power in the cycling time trial, and less distance covered among the mentally fatigued participants.

The research team has already started to test the links between mental fatigue and performance among groups of elite athletes in ‘real world’ exercise scenarios.

About this exercise and mental fatigue research news

Author: Beck Lockwood
Source: University of Birmingham
Contact: Beck Lockwood – University of Birmingham
Image: The image is in the public domain

Original Research: Closed access.
Mental Fatigue: The Cost of Cognitive Loading on Weight Lifting, Resistance Training, and Cycling Performance” by Chris Ring et al. International Journal of Sports Physiology and Performance


Mental Fatigue: The Cost of Cognitive Loading on Weight Lifting, Resistance Training, and Cycling Performance

Purpose: Mental fatigue (MF) can impair physical performance in sport. We tested the hypothesis that cognitive load alone, and intermixed with standard resistance training, would induce MF, increase rating of perceived exertion (RPE), alter perception of weight lifting and training, and impair cycling time-trial performance. 

Methods: This 2-part study employed a within-participant design. In part 1, after establishing leg-extension 1-repetition maximum (1RM), 16 participants lifted and briefly held weights at 20%, 40%, 60%, and 80% of 1RM. RPE and electromyography (EMG) were measured for each lift. During the testing sessions, participants completed cognitive tasks (MF condition) or watched neutral videos (control condition) for 90 minutes before lifting the weights.

In part 2, they completed submaximal resistance training comprising 6 weight training exercises followed by a 20-minute cycling time trial. In the MF condition, they completed cognitive tasks before and between weight training exercises. In the control condition, they watched neutral videos. Mood (Brunel Mood Scale), workload (National Aeronautics and Space Administration Task Load Index), MF-visual analogue scale (MF-VAS), RPE, psychomotor vigilance, distance cycled, power output, heart rate, and blood lactate were measured. 

Results: In part 1, the cognitive task increased lift-induced RPE (P = .011), increased MF-VAS (P = .002), and altered mood (P < .001) compared with control. EMG did not differ between conditions. In part 2, the cognitive tasks increased RPE (P < .001), MF-VAS (P < .001), and mental workload (P < .001), but reduced cycling time-trial power (P = .032) and distance (P = .023) compared with control. Heart rate and blood lactate did not differ between conditions. 

Conclusion: A state of MF induced by cognitive load, alone or intermixed with physical load, increased RPE during weight lifting and training and impaired subsequent cycling performance.

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