Caffeine intake reverses the impairment of sleep restriction on high-intensity exercise performance

We investigated whether caffeine ingestion reverses the deleterious effect of sleep restriction on high-intensity exercise (HIE) performance, and its impact on ventilatory, blood acidosis, and neuromuscular fatigue. Nine physically active men (29 ± 6 years, 176 ± 5 cm, 80.4 ± 7.4 kg) completed a session of HIE under: (1) habitual sleep plus placebo ingestion (HSP); (2) sleep restriction plus placebo ingestion (SRP); and (3) sleep restriction plus 5 mg.kg^-1 of caffeine ingestion (SRC). Ventilatory responses were continually monitored, while blood H⁺, plasma lactate, maximal voluntary isometric contraction (MVIC), voluntary activation (VA), and quadriceps potentiated doublet-twitch force (PT) were assessed at pre-capsule ingestion, after completing 70% of the HIE, and at task failure. Time to task failure was shorter (p < 0.001) in SRP (6.23 ± 2.11 min) than in HSP (7.68 ± 2.92 min) and SRC (7.83 ± 3.19 min), without differences between HSP and SRC (p = 0.96). Sleep restriction reduced minute ventilation (~6%) and tidal volume (~7%) and increased respiratory frequency (~5%) near to the end of HIE (p < 0.05); caffeine ingestion, however, reverted these effects of sleep restriction. Blood H⁺ was higher (~34%) and plasma lactate lower (~21%) at post-exercise in SRP than in HSP and SRC (p < 0.05), but similar between HSP and SRC (p > 0.05). The VA decreased (p < 0.05) from pre- to post-exercise in SRP (4 ± 5%), but not in HSP and SRC (p > 0.05). The MVIC and PT decreased similarly from pre- to post-exercise in all conditions (p < 0.05). Caffeine ingestion reverses the impairment of sleep restriction on HIE performance, likely by restoring normal ventilatory pattern and preventing sleep restriction-induced exacerbated acidosis and central fatigue.