Exerting cognitive control can lead to mental fatigue and impair self-regulation of subsequent physical performance. However, current understanding is limited due to a number of factors. First, studies have employed manipulations involving either high or low cognitive demands, failing to test whether a dose-response relationship exists between mental fatigue and physical performance. Second, the role of several psychological variables among the mental fatigue – physical performance relationship remains unclear. Third, current literature lacks generalizability in that existing findings have largely been derived from studies involving active samples performing physical tasks that the general population may not commonly engage in for health and fitness benefits. Lastly, there has been little research examining intervention strategies that may attenuate the effects of mental fatigue on physical activity behaviour. This dissertation aimed to advance our understanding of self-regulation of physical activity behaviour in response to mental fatigue by addressing shortcomings within the literature discussed above.
Study 1 examined whether a dose-response relationship exists for mental fatigue and physical performance. Results showed a performance threshold exists between 4 and 6 minutes of exposure to a mentally fatiguing cognitive control task. Beyond this threshold, task self-efficacy also showed uniform reductions which mediated the mental fatigue – physical performance change relationship. Findings are consistent with previous research and reveal self-efficacy is a key variable that accounts for the negative effects of mental fatigue on physical performance.
Study 2 investigated the hypothesis that offering a performance contingent monetary incentive would attenuate the negative carryover effects of mental fatigue on physical performance. Findings showed mental fatigue caused characteristic declines in physical performance; however, incentives countered the effects of mental fatigue and led to performances equal to those witnessed in a non-fatigued state. Interestingly, incentives did not provide any additional benefit for performance when not fatigued. Findings support motivational accounts of self-regulation, although incentives may lack practicality and may not be a cost-effective means to alter exercise behaviour.
Study 3 examined the effect of mental fatigue on intended physical exertion and exercise performance reflective of current public health guidelines for physical activity in a sample comprised of insufficiently active university students. Findings showed mental fatigue alters the amount of physical effort people are willing to invest in an exercise workout and follow through with those intentions by doing less work and exercising at a lower heart rate intensity. These are the first results showing people may deliberately adjust their physical effort to cope with mental fatigue.
Study 4 investigated whether heart rate biofeedback moderates the effects of mental fatigue on vigorous-intensity exercise reflective of current public health physical activity guidelines and the effects of mental fatigue on pre-exercise motivational cognitions. Results showed mental fatigue was associated with decreases in intended physical effort and commitment to vigorous-intensity exercise goals which corresponded with reductions in exercise intensity (i.e., HRAVE) and total work performed when people exercised without feedback. However, HR biofeedback attenuated the negative carryover effects of mental fatigue on exercise behaviour, restoring exercise intensity and performance to levels witnessed in a non-fatigued state. Similar to incentives, biofeedback offered no further benefits for performance when not fatigued. Findings align with predictions of Control Theory and suggest biofeedback using widely available physical activity monitors in combination with goals can improve intensity-based physical activity guideline adherence when confronted with barriers such as mental fatigue. / Thesis / Doctor of Philosophy (PhD) / Effortful cognitive control exertion can lead to mental fatigue and impair self-regulation of subsequent physical performance. However, current understanding is limited due to a number of factors. This thesis addressed several gaps in the literature through a systematic examination of potential mediators and moderators of the mental fatigue - physical performance relationship. Findings revealed downstream physical performance impairments are dependent on exceeding a critical mental fatigue threshold. Reductions in pre-exercise cognitions including self-efficacy, intended physical exertion and goal commitment all correspond with negative changes in exercise performance. Evidence also highlights the generalizability of fatigue-induced effects by demonstrating that insufficiently active people engaging in exercise for health and fitness benefits down-regulate exercise performance in the face of mental fatigue. Incentives and heart rate biofeedback can attenuate the effects of mental fatigue on physical performance. Collectively, evidence provides insight for theories of self-control and can be interpreted within Muller and Apps (2018) neurocognitive framework of motivational fatigue.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24151 |
| Date | January 2018 |
| Creators | Brown, Denver |
| Contributors | Bray, Steven, Kinesiology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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