Phosphatidylserine (PS) is an essential component of all biological membranes and is required for normal cellular structure and function. The participation in physical activity often challenges a variety of physiological systems; consequently, the ability to maintain normal cellular function during activity can determine sporting performance. PS has been established as a safe oral supplement [1
] capable of attenuating the serum cortisol [2
] and creatine kinase [4
] responses to acute exercise stress. In addition, PS has been reported to improve subjective measures of overtraining such as perceived muscle soreness and well-being [5
]. These finding suggest that PS partly counteracts the stress-induced activation of the hypothalamo-pituitary-adrenal (HPA) axis [6
In addition to physical stress, PS supplementation benefits subjects suffering from mental stress. PS supplementation has been reported to improve mood in a sub-group of healthy young adults when faced with a stressful mental task [7
] and blunted both serum ACTH and cortisol, and salivary cortisol responses to the Trier Social Stress Test (TSST) [8
A recent study by Kingsley et al. showed no effect of oral PS supplementation on markers of muscle damage or perceived soreness, however, PS tended to improve sprint and exercise performances when compared to placebo [9
]. These findings do suggest that PS might possess ergogenic properties. The effective daily dosages in sport studies range from 300 to 800 mg PS for short-term application (10–15 days) and from 300 to 400 mg PS for 3 to 4 weeks for mental stress [10
]. The lowest effective dose for athletes is yet unknown [10
These findings suggest that PS supplementation might be beneficial for sports demanding high levels of concentration and coordination such as the game of golf. The golf swing requires the interaction of the central nervous system and skeletal muscles as well as the correct combination of power, velocity and endurance. The golf swing is a complex motion and especially teeing off and putting creates high levels of tension. Salivary cortisol levels have been reported to significantly increase in elite male golfers [11
]. Individual and external expectations [13
] and the importance of the first stroke result in mental stress during tee-off. This might result in negative effects on performance due to an inaccuracy in striking the ball. The tee-off from a stationary location such as a driving range is an ideal study exercise since it allows the easy measure of the effects of stressors on performance parameters such as ball flight. Additional stress can be created by a time restriction between tee offs and by the creation of competitive target task.
Based on this background, the present study assessed the effects of PS supplementation on perceived stress and performance in golfers during tee-off from a driving range. For the first time, a functional food (nutritional bar) was used as study material in a nutritional intervention study on golf performance. This study further investigates the yet lowest daily dose of PS supplementation when faced with a stressful task.