5-Hydroxymethylfurfural and α-ketoglutaric acid supplementation increases oxygen saturation during prolonged exercise in normobaric hypoxia.

This double-blinded, randomized and placebo-controlled, crossover study investigated whether α-ketoglutaric-acid (α-KG) and 5-hydroxymethylfurfural (5-HMF) supplementation improves exercise performance in hypoxia and affects physiological responses during the exercise task. Eight moderately trained male participants (age: 25.3 ± 2.0 y, VO2max: 48.0 ± 8.3 ml/min/kg) performed an incremental exercise test to exhaustion in normoxia and two 2-hour cycle time trial (TT) tests in hypoxia (3,500 m) each separated by 1-week. Prior to the TT, participants supplemented with either α-KG and 5-HMF or placebo (random order). Supplementation did not improve TT performance at altitude and did not affect heart rate, effort perception and oxidative stress levels (p > 0.05). Oxygen saturation (SpO2) was enhanced during the α-KG and 5-HMF supplementation trial (79.5 ± 3.3 vs. 78.2 ± 3.7%, p = 0.026). Even though TT performance was unaffected, the enhanced SpO2 - possibly originated from changed O2-affinity - deserves further consideration as the exercise performance decline at altitude is strongly linked to the SpO2 decline. The inclusion of moderately fit participants, not specifically cycle trained, might have prevented any visible performance enhancement.