Caffeine and performance in altitude: endurance performance in acute hypoxia following 4 mg·kg-1 caffeine ingestion

Abstract

Introduction: Various studies have observed improved endurance performance (EP) following caffeine ingestion (CAF) at lowland. However, the effects CAF have on an endurance performance in altitude have so far been given little scientific interest. This master thesis was therefore designed to study the effects of CAF on an 8 km crosscountry poling performance test (8 km C-PT) during acute exposure to altitude (2000 meters above sea-level). Physiological measurements during a submaximal incremental test prior to the 8 km C-PT were conducted to understand possible mechanisms behind an eventually improved performance. Method: The study had a randomized, double-blinded, cross-over design. 9 highly trained cross-country skiers fulfilled the inclusion criteria’s. All test subjects underwent familiarization training prior to the main tests on a cross-country poling ergometer (CCPOL). One 8 km C-PT was performed in lowland and two 8 km C-PT was conducted in altitude. Half of the TS were given CAF (4 mg • kg-1) the first 8 km C-PT in altitude and the other half received placebo (PLA). Logically TS were given opposite treatment on the second and last 8 km C-PT. Before each 8 km C-PT TS performed a submaximal incremental test of four 5-minute workloads. Exercise intensity was 55-70 % of the individual VO2max-altitude. Results: Results show a small but possible enhancing effect on the time to complete the 8 km C-PT following caffeine ingestion compared to placebo. Average time used in altitude was 32.36 ± 2.24 minutes after caffeine ingestions and 32.78 ± 2.45 after placebo. The enhanced performance was mainly due to a higher velocity the first 3 km of the test. Time used on the 8 km C-PT at lowland was 30.99 ± 3.32 minutes. Lactate concentrations were significantly increased both during the incremental test and after the 8 km C-PT in altitude following caffeine ingestion. Heart rate was significantly increased and blood bicarbonate significantly decreased following caffeine ingestions during the 8 km C-PT. In addition, no difference in muscular pain was observed during the performance-test, but subject reported lower perception of pain in the arms after three of the four submaximal workloads. Conclusion: Caffeine ingestion showed a possible enhancing effect on time to complete the 8 km CPT. The increased HR seen during the 8 km C-PT would indicate that TS was able to work harder following caffeine ingestion compared to placebo. Although no differences in RPE was reported one might imagine caffeine, due to the increased workload, actually lowers RPE.