Caffeine Increased Muscle Endurance Performance Despite Reduced Cortical Activation and Unchanged Neuromuscular Efficiency and Corticomuscular Coherence

Nutrients. 2019 Oct 15;11(10):2471. doi: 10.3390/nu11102471.


The central and peripheral effects of caffeine remain debatable. We verified whether increases in endurance performance after caffeine ingestion occurred together with changes in primary motor cortex (MC) and prefrontal cortex (PFC) activation, neuromuscular efficiency (NME), and electroencephalography-electromyography coherence (EEG-EMG coherence). Twelve participants performed a time-to-task failure isometric contraction at 70% of the maximal voluntary contraction after ingesting 5 mg/kg of caffeine (CAF) or placebo (PLA), in a crossover and counterbalanced design. MC (Cz) and PFC (Fp1) EEG alpha wave and vastus lateralis (VL) muscle EMG were recorded throughout the exercise. EEG-EMG coherence was calculated through the magnitude squared coherence analysis in MC EEG gamma-wave (CI > 0.0058). Moreover, NME was obtained as the force-VL EMG ratio. When compared to PLA, CAF improved the time to task failure (p = 0.003, d = 0.75), but reduced activation in MC and PFC throughout the exercise (p = 0.027, d = 1.01 and p = 0.045, d = 0.95, respectively). Neither NME (p = 0.802, d = 0.34) nor EEG-EMG coherence (p = 0.628, d = 0.21) was different between CAF and PLA. The results suggest that CAF improved muscular performance through a modified central nervous system (CNS) response rather than through alterations in peripheral muscle or central-peripheral coupling.

Keywords: EEG–EMG coherence; ergogenic; fatigue; placebo.

MeSH terms

  • Adult
  • Alpha Rhythm / drug effects*
  • Bicycling
  • Caffeine / administration & dosage*
  • Caffeine / adverse effects
  • Cross-Over Studies
  • Double-Blind Method
  • Electromyography
  • Humans
  • Motor Cortex / drug effects*
  • Motor Cortex / physiology
  • Muscle Contraction / drug effects*
  • Muscle Fatigue
  • Muscle Strength / drug effects
  • Performance-Enhancing Substances / administration & dosage*
  • Performance-Enhancing Substances / adverse effects
  • Physical Endurance / drug effects*
  • Prefrontal Cortex / drug effects*
  • Prefrontal Cortex / physiology
  • Quadriceps Muscle / innervation*
  • Time Factors


  • Performance-Enhancing Substances
  • Caffeine