Caffeine Expectancy Does Not Influence the Physical Working Capacity at the Fatigue Threshold.
Study Goal
The researchers aimed to determine whether caffeine expectancy influences neuromuscular fatigue, as measured by the physical working capacity at the fatigue threshold (PWCFT).
Results Summary
The study found that caffeine consumption significantly improved maximal power output, PWCFT, and heart rate at end exercise compared to placebo, but expectancy alone (without actual caffeine) did not produce significant effects.
Population
8 healthy college-aged men (mean age 25.6 ± 1.0 years).
Effective Dosage
Not specified in the abstract.
Duration
4 experimental conditions, each separated by 7 days.
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
caffeine consumption | increase | maximal power output | 8 healthy college-aged men | F(3, 21) = 11.75; p < 0.001 | significantly higher mean values | #1 |
caffeine consumption | increase | physical working capacity at the fatigue threshold (PWCFT) | 8 healthy college-aged men | F(3, 21) = 12.28; p < 0.001 | significantly higher mean values | #2 |
caffeine consumption | increase | PWCFT (%maximal power output) | 8 healthy college-aged men | F(3, 21) = 8.75; p < 0.001 | significantly higher mean values | #3 |
caffeine consumption | increase | heart rate at end exercise (%predicted) | 8 healthy college-aged men | F(3, 21) = 3.83; p = 0.025 | significantly higher mean values | #4 |
caffeine consumption | no change | physical working capacity at the fatigue threshold (PWCFT) | 8 healthy college-aged men | - | no statistically significant mean differences | #5 |
Ambrozy, CA, Hawes, NE, Hayden, OL, Sortzi, I, and Malek, MH. Caffeine expectancy does not influence the physical working capacity at the fatigue threshold. J Strength Cond Res 38(6): 1056-1062, 2024-The placebo effect occurs when a desired outcome is experienced due to the belief that a treatment is effective, even in the absence of an active ingredient. One explanation for this effect is based on a person's expectations of a drug or supplement. Although caffeine's effects on sports performance have been studied, little is known about how expectations of caffeine affect neuromuscular fatigue during continuous muscle action. The physical working capacity at the fatigue threshold (PWCFT) can be used to assess neuromuscular fatigue noninvasively using surface electromyography. Thus, the purpose of this study was to investigate whether caffeine expectancy influences PWCFT. We hypothesized that regardless of expectancy, caffeine consumption would delay neuromuscular fatigue. The study involved 8 healthy college-aged men (mean ± SEM: age, 25.6 ± 1.0 years) who visited the laboratory on 4 occasions, each separated by 7 days. The subjects completed 4 experimental conditions, in random order, where they were told that they were consuming caffeine or placebo and either received caffeine or placebo. After consuming the drink, the subjects remained in the laboratory for an hour and then performed an incremental exercise test. The results showed that the condition where subjects were told that they were consuming caffeine and received caffeine had significantly higher mean values for maximal power output (F(3, 21) = 11.75; p < 0.001), PWCFT (F(3, 21) = 12.28; p < 0.001), PWCFT (%maximal power output; F(3, 21) = 8.75; p < 0.001), and heart rate at end exercise (%predicted; F(3, 21) = 3.83; p = 0.025) compared with the 2 conditions where placebo was received. However, no statistically significant mean differences were found from the condition where subjects were told that they were consuming placebo but consuming caffeine. This suggests that a person's expectancy and potential somatic response may serve as a cue for how an ergogenic aid or placebo could affect subsequent performance.