Effects of Phenylcapsaicin on Aerobic Capacity and Physiological Parameters in Active Young Males: a Randomized, Triple-blinded, Placebo-controlled, Crossover Trial

Phenylcapsaicin (PC) is a new capsaicin analog which has exhibited a higher bioavailability. This sudy assessed the effects of a low dose (LD) of 0.625 mg and a high dose (HD) of 2.5 mg of PC on aerobic capacity, substrate oxidation, energy metabolism and exercise physiological variables in young males. Seventeen active males (age = 24.7 ± 6.0 years) enrolled to this randomized, triple-blinded, placebo-controlled, crossover trial. Participants attended the laboratory on 4 sessions separated by 72-96 h. A submaximal exercise test [to determine maximal fat oxidation (MFO) and the intensity at MFO (FATmax)] followed by a maximal incremental test (to determine VO2) were performed in a preliminary session. The subsequent sessions only differed in the supplement ingested [LD, HD or placebo (PLA)] and consisted of a steady-state test (60 min at FATmax) followed by a maximal incremental test. Energy metabolism, substrate oxidation, heart rate, general (gRPE) and quadriceps (RPEquad) rate of perceived exertion, skin temperature and thermal perception were tested. Clavicle thermal perception was lower in HD compared to PLA and LD ( = 0.04) across time. HD reduced maximum heart rate in comparison to PLA and LD ( = 0.03). LD reported higher general RPE (RPEg) values during the steady-state test compared to PLA and HD across time ( = 0.02). HD and LD elicited higher peak of fat oxidation during the steady-state test compared with PLA ( = 0.05). Intra-test analyses revealed significant differences for fat oxidation (FATox) in favor of HD and LD compared to PLA ( 0.002 and 0.002, respectively), and for carbohydrate oxidation (CHOox) ( 0.05) and respiratory exchange ratio (RER) ( 0.03) for PLA. In the incremental test, only general RPE at 60% of the maximal intensity (W) differed favoring HD ( ≤ 0.05). Therefore, PC may contribute to increase aerobic capacity through the improvement of fat oxidation, maximum heart rate and perceptual responses during exercise.