Placebo Effect of Caffeine on Physiological Parameters and Physical Performance

Area of Science:

• Sports Science
• Human Physiology
• Psychology

Background:

• The placebo effect is a well-documented phenomenon in various medical and performance contexts.
• Caffeine is a widely used ergogenic aid, but its effects can be influenced by psychological factors.
• Understanding the placebo effect in relation to caffeine and strength performance is crucial for athletes and researchers.

Purpose of the Study:

• To investigate the placebo effect of a high dose of caffeine (9 mg/kg) on physiological and performance measures.
• To analyze the impact of placebo on heart rate, heart rate variability, and strength tests.
• To evaluate perceived performance, effort, and side effects associated with the placebo condition.

Main Methods:

• 18 strength-trained participants underwent two trial days: one with caffeine-informed placebo ingestion and one control (no ingestion).
• Measurements included resting heart rate and heart rate variability (HRV) before strength assessments.
• Participants performed bench press and squat tests at varying intensities (50%, 75%, 90% of 1RM), followed by subjective evaluations.

Main Results:

• No significant differences were observed in most strength performance variables between placebo and control conditions.
• Resting heart rate decreased (p=0.040) and mean RR interval increased (p=0.032) in the placebo trial.
• Heart rate variability, perceived performance, and effort remained similar; however, side effects like nervousness were reported with the placebo.

Conclusions:

• The placebo effect, in this high-dose caffeine context, did not enhance strength performance, HRV, or perceived effort.
• A significant reduction in resting heart rate and an increase in mean RR interval were noted under placebo conditions.
• The study highlights that psychological factors can elicit physiological changes and subjective experiences, even without direct pharmacological effect on performance.