In untrained male cyclists, evening caffeine ingestion is associated with a 2.9% improvement in 3-km cycling performance, whereas trained male cyclists show no significant change in performance under the same conditions, indicating that training status modifies the ergogenic effect of caffeine during evening exercise.

Caffeine blocks a natural chemical in muscles that slows down nerve signals, allowing more muscle fibers to fire during cycling, especially when pedaling at a steady, moderate pace. This gives untrained cyclists more power without needing to pedal harder, improving their race time. Trained cyclists already use their muscles efficiently, so this extra push doesn't help them.