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Updated: Jun 25, 2025
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Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test
Published on: July 27, 2015
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Caffeine Expectancy Does Not Influence the Physical Working Capacity at the Fatigue Threshold.
Christina A Ambrozy1,2, Nicole E Hawes1,2, Olivia L Hayden1,2
1Physical Therapy Program, Department of Health Care Sciences, College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan; and.
Journal of Strength and Conditioning Research
|May 23, 2024
Summary
Caffeine expectancy did not influence physical working capacity at the fatigue threshold. However, when individuals believed they received caffeine, it enhanced performance, suggesting expectation plays a role in ergogenic aid effects.
Area of Science:
- Exercise Physiology
- Sports Science
- Nutritional Science
Background:
- The placebo effect, driven by expectations, can influence outcomes even without active ingredients.
- While caffeine's performance benefits are known, its impact on neuromuscular fatigue influenced by expectation is less understood.
- Physical working capacity at the fatigue threshold (PWCFT) offers a non-invasive measure of neuromuscular fatigue.
Purpose of the Study:
- To investigate if caffeine expectancy affects physical working capacity at the fatigue threshold (PWCFT).
- To determine the influence of perceived caffeine intake versus actual caffeine intake on neuromuscular fatigue.
- To explore the role of expectation in the ergogenic effects of caffeine.
Main Methods:
- Eight healthy college-aged men participated in four laboratory sessions, each separated by a week.
- Participants were randomly assigned to one of four conditions: told caffeine/received caffeine, told placebo/received placebo, told caffeine/received placebo, told placebo/received caffeine.
- Following ingestion, participants rested for one hour before completing an incremental exercise test to assess PWCFT via surface electromyography.
Main Results:
- Maximal power output, PWCFT, PWCFT as a percentage of maximal power output, and heart rate at end exercise were significantly higher when participants were told they received caffeine and actually received caffeine, compared to placebo conditions.
- No significant differences in performance were observed when participants were told they received placebo but actually consumed caffeine.
- These findings indicate that the belief in consuming caffeine, alongside actual consumption, significantly impacts performance metrics.
Conclusions:
- Caffeine expectancy alone does not appear to alter physical working capacity at the fatigue threshold.
- The belief in consuming caffeine, coupled with actual intake, enhances exercise performance and capacity.
- Expectations and associated physiological responses may act as crucial mediators for the effects of ergogenic aids and placebos.
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