Caffeine & Exercise: Does It Help at High Altitude?

study PMID: 40675560

Quick Summary: This study looked at how caffeine affects exercise performance in both normal conditions and at simulated high altitude. It found that caffeine didn't boost peak performance, but it did help with breathing and made exercise feel easier during moderate activity, especially in low-oxygen environments.

Does Caffeine Boost Exercise Performance?

The research team wanted to know if caffeine could improve how well people exercise, especially when there's less oxygen available, like at high altitudes. They found that caffeine didn't improve how much oxygen people could use at their peak effort.

Study Details

Who was studied: 29 healthy, active adults (14 women and 15 men).

How long: Each person did four different exercise tests.

What they took: Participants took either a caffeine dose (6mg per kilogram of body weight) or a placebo (a sugar pill) 45 minutes before exercising. They exercised in both normal air and air with less oxygen, simulating high altitude.

What This Means For You

Caffeine won't make you a super athlete at altitude: If you're training or competing at high altitude, caffeine probably won't help you reach a higher peak performance level.

Caffeine might help with moderate exercise: During less intense exercise, caffeine could make breathing easier and make the exercise feel less difficult, especially in low-oxygen environments.

Listen to your body: Pay attention to how caffeine affects you. Some people are more sensitive to it than others.

Study Limitations

Small group: The study only included a small number of people, so the results might not apply to everyone.

Short exercise: The exercise tests were relatively short. Caffeine's effects on longer endurance activities aren't clear.

One dose: The study only used one dose of caffeine. We don't know if different amounts would have different effects.

Simulated altitude: The study used simulated altitude, not real high-altitude exposure.

Key Findings

This study found that caffeine (6 mg/kg) did not improve maximal aerobic power or peak oxygen uptake (VO₂peak) in either normoxic or hypoxic conditions. However, during steady-state cycling at 40% normoxic power, caffeine increased pulmonary ventilation (+2.1 L/min, p = .026) and reduced perceived exertion (p = .026). Caffeine also mitigated hypoxia-induced decreases in vastus lateralis oxygenation (52 ± 8% vs. 50 ± 10%, p = .020) but did not affect pulse oxygen saturation (SpO₂) or overall exercise capacity.

Study Design

This was a randomized, double-blind, placebo-controlled crossover trial involving 29 healthy, active adults (14 women, 15 men; age and weight unspecified). Participants underwent four experimental conditions in a pseudo-randomized order: caffeine/placebo × normoxia/hypoxia (simulated ∼3,500 m altitude). Each session included 10 minutes of steady-state cycling followed by an incremental exercise test to exhaustion. Cardiorespiratory parameters, muscle oxygenation, and perceived exertion were measured.

Dosage & Administration

Participants ingested 6 mg/kg body mass of anhydrous caffeine or placebo 45 minutes before exercise. The caffeine dose was standardized to body weight, ensuring individualized administration.

Results & Efficacy

Peak Exercise: Hypoxia reduced VO₂peak (44.8 ± 7.3 vs. 51.4 ± 7.9 ml·kg⁻¹·min⁻¹, p < .001) and SpO₂ (p < .001), but caffeine showed no significant effects (VO₂peak: p = .501; SpO₂: p = .898).
Steady-State Cycling: Caffeine increased pulmonary ventilation (p = .026) and improved vastus lateralis oxygenation in hypoxia (p = .020), but not in normoxia (p > .999). Hypoxia alone decreased SpO₂ (p < .001), with no attenuation by caffeine (interaction p = .283).
Perceived Exertion: Hypoxia increased exertion (p < .001), while caffeine reduced it (p = .026).
Heart Rate: Caffeine elevated heart rate in both conditions (p < .001).

Limitations

Small sample size (n = 29) and unequal gender distribution (14 women) may limit generalizability.
Short exercise duration (10-minute steady-state + incremental test) may not reflect prolonged endurance performance.
Single caffeine dose (6 mg/kg) without dose-response analysis; effects at lower/higher doses remain unknown.
Hypoxia was acute (simulated altitude), not chronic, limiting applicability to long-term altitude exposure.
No performance time measurement—only capacity and physiological markers were assessed.

Clinical Relevance

For individuals exercising in hypoxic environments (e.g., high-altitude training), caffeine may modestly improve ventilation and reduce perceived exertion during moderate-intensity activity. However, it does not enhance maximal aerobic capacity or counteract hypoxia-induced oxygen desaturation. Athletes should not expect caffeine to improve peak performance at altitude, though it might support endurance during submaximal efforts. These findings suggest caffeine’s ergogenic benefits are context-dependent, with limited utility in severe hypoxia. Practical use should consider individual tolerance to caffeine and the intensity/duration of altitude exposure.