Author(s): MARANESI, B., PIRES, F.O., RIBEIRO, W.A., Institution: UNIVERSITY OF SÃO PAULO, Country: BRAZIL, Abstract-ID: 697

INTRODUCTION:
Caffeine (CAF) is a well-established ergogenic aid with documented analgesic properties. Paracetamol (PCT), a widely used analgesic, has also been proposed to enhance exercise performance through central mechanisms. Whether their combined ingestion potentiates ergogenic and analgesic effects when exercise is initiated in the presence of pre-existing muscle pain remains unclear.
METHODS:
Eighteen healthy men completed a randomized, triple-blind, crossover study. Participants performed a cycling time-to-exhaustion test (TTE) at 80% of peak power output (Wpeak) under four conditions: placebo (PLA), caffeine (CAF; 6 mg·kg⁻¹), paracetamol (PCT; 20 mg·kg⁻¹), and CAF+PCT. Muscle pain was experimentally induced via intramuscular hypertonic saline injection prior to each trial. The TTE was initiated under moderate pain approximately 50 minutes after ingestion.
Time to exhaustion, electromyographic activity (EMG), pain perception, rating of perceived exertion (RPE), and affect were assessed.
Data were analyzed using repeated-measures ANOVA. When significant main effects were detected, pairwise comparisons were performed with Bonferroni adjustment. Effect sizes were calculated using Cohen’s d and interpreted according to conventional thresholds. Statistical significance was set at p ≤ 0.05.

RESULTS:
A main effect of condition was observed for performance (F = 2.91, p = 0.04, d = 0.58), with CAF increasing time to exhaustion compared to PLA (p = 0.03). A main effect was also found for pain (F = 4.50, p = 0.004, d = 0.73), as both CAF (p = 0.01) and CAF+PCT (p = 0.01) reduced pain during exercise compared to PLA. However, neither PCT alone nor CAF+PCT improved performance. EMG responses were not meaningfully altered across conditions.
CONCLUSION:
Isolated caffeine ingestion improved endurance performance despite the presence of experimentally induced muscle pain, extending previous evidence obtained under pain-free conditions. Although both CAF and CAF+PCT reduced perceived pain, only CAF enhanced performance, suggesting that pain attenuation combined does not fully explain ergogenic effects. The absence of performance enhancement with CAF+PCT indicates a potential pharmacological interaction attenuating caffeine’s ergogenic action. Caffeine enhances cycling performance and reduces perceived pain when exercise is initiated under moderate muscle pain. Paracetamol, alone or combined with caffeine, does not provide additional ergogenic benefit under these conditions