Caffeine bars used as pre-exercise supplements influence endurance performance, energy metabolism and perception of effort in trained cyclists

Abstract

Background: In contrast to caffeine bars, the effect of caffeine intake from tablets and energy drinks on endurance performance has already been investigated. Therefore, the aim of the study is to examine the effects of caffeine bars used as pre-exercise supplements on endurance performance in cycling.

Methods: The present study was designed as a randomized single-blind cross-over placebo-controlled trial. Nine male, trained cyclists completed endurance exercises on a cycling ergometer under the following conditions: ingestion of water (WAT), placebo bars (PLA) and caffeine bars (CAF; 5 mg caffeine/kg bodyweight), respectively, 45 min prior to the test. After 40 min at a constant intensity of 75% VO₂max (assessed in a previously performed incremental test) load was increased 10 W/min until exhaustion.

Results: CAF compared to PLA resulted in a higher maximal power and longer time to exhaustion (p = .002). Surprisingly, concentration of free fatty acids was lower at exhaustion (p = .004), whereas blood lactate levels (p = .021) and heart rate (p = .008) were significantly higher after CAF. Subjects also reported lower received perception of effort at warm-up (0.034), 30 min (p = .026) and 40 min (p = .041) only after CAF.

Conclusions: Caffeine bars are useful pre-exercise supplements. Their performance enhancing effect was rather due to a delayed perception of fatigue than an increased lipolysis, proving caffeine as central nervous system stimulant.