Purpose: The purpose of the study was to investigate the effects of 750 mg of soybean-derived phosphatidylserine, administered daily for 10 d, on exercise capacity, oxygen uptake kinetic response, neuroendocrine function, and feeling states during exhaustive intermittent exercise.
Methods: Following preliminary testing, fourteen active males completed a staged intermittent exercise protocol on two further occasions (T1 and T2) separated by 16 ± 1 d. The protocol consisted of three 10-min stages of cycling at 45, 55, and 65% V̇O2max, followed by a final bout at 85% V̇O2max that was continued until exhaustion. Approximately 5 d after T1 the subjects were assigned, in a double-blind manner, to either phosphatidylserine (PS) or placebo (P). Breath-by-breath respiratory data and heart rate were continually recorded throughout the exercise protocol, and blood samples were obtained at rest, during the rest periods within the protocol (Post-55, Post-65), at the end of exercise (Post-85), 20 min after the completion of exercise (postexercise), and the day following exercise (Post-24 h).
Results: The main finding of this study was that supplementation had a significant effect on exercise time to exhaustion at 85% V̇O2max (P = 0.005). The exercise time to exhaustion in PS increased following supplementation (7:51 ± 1:36 to 9:51 ± 1:42 min:s, P = 0.001), whereas P remained unchanged (8:09 ± 0:54 to 8:02 ± 0:54 min:s, P = 0.670). Supplementation did not significantly affect oxygen kinetic mean response times (MRTon and MRToff), serum cortisol concentrations, substrate oxidation, and feeling states during the trial.
Conclusion: This is the first study to report improved exercise capacity following phosphatidylserine supplementation. These findings suggest that phosphatidylserine might possess potential ergogenic properties.
1University of Wales Swansea, Swansea, Wales, UNITED KINGDOM; and 2Queen's University of Belfast, Belfast, Ireland, UNITED KINGDOM
Address for correspondence: M. Kingsley, Department of Sports Science, University of Wales Swansea, Vivian Tower, Singleton Park, Swansea, SA2 8PP; E-mail: M.I.C.Kingsley@Swansea.ac.uk.
Submitted for publication September 2004.
Accepted for publication August 2005.
The authors wish to acknowledge Mrs R.E. Dietzig for her technical assistance during the study, and the laboratory staff from Queen's University and the Royal Group of Hospitals for their assistance in the serum cortisol analysis. In addition, we would like to thank Lucas Meyer for supplying the supplements.