Supplementation with a low-dose of octopamine does not influence endurance cycling performance in recreationally active men

Abstract

Objectives: The aim of this study was to examine the influence of octopamine supplementation on endurance performance and exercise metabolism.

Design: Double-blind cross-over study.

Methods: Ten healthy, recreationally active men (Mean±SD; age: 24±2 years; body mass: 78.4±8.7kg; VO_2peak: 50.5±6.8 mLkg^-1min^-1) completed one VO_2peak test, one familiarisation trial and two experimental trials. After an overnight fast, participants ingested either a placebo or 150mg of octopamine 60min prior to exercise. Trials consisted of 30min of cycle exercise at 55% peak power output, followed by a 30min performance task whereby participants completed as much work (kJ) as possible.

Results: Performance was similar between the experimental trials (placebo: 352.8±39kJ; octopamine: 350.9±38.3kJ; Cohen's d effect size=0.05; p=0.380). Substrate oxidation and circulating concentrations of free fatty acids, prolactin and cortisol were similar between trial conditions (all p>0.05). There were also no differences across trials for heart rate or perceived exertion during exercise (both p>0.05).

Conclusions: Acute supplementation with a low dose of octopamine did not influence endurance cycle performance, substrate oxidation or circulating hormonal concentrations, which could be due to the low serum octopamine concentrations observed. Future studies should investigate the influence of larger doses of octopamine in recreationally active and well-trained individuals during prolonged exercise in temperate and high ambient conditions.

Keywords: Exercise; Fatigue; Stimulants; Substrate oxidation; Supplements.