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Phosphatidylserine and its effects on intermittent exercise. / Mark Philip Miller
Swansea University Author: Mark Philip, Miller
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Phosphatidyl serine (PS) is a naturally occurring phospholipid nutrient that is predominantly found in the membrane of cells. The biochemical actions of PS have been demonstrated to include; for example: (1) regulation of calcium uptake (Floreani et al, 1991); (2) stimulation of ATPase activity (Tsa...
|Degree level:||Master of Philosophy|
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Phosphatidyl serine (PS) is a naturally occurring phospholipid nutrient that is predominantly found in the membrane of cells. The biochemical actions of PS have been demonstrated to include; for example: (1) regulation of calcium uptake (Floreani et al, 1991); (2) stimulation of ATPase activity (Tsakiris and Deliconstantinos, 1984); and (3) activation of different Protein Kinase-C (PKC) isoforms (Kaibuchi et al., 1981). Previous research has shown that supplementation with 800 mg day[-1] of bovine cortex-PS (BC-PS) for 10 days attenuated the adrenocorticotrophin and cortisol responses to intermittent exercise (Monteleone et al., 1992). Unfortunately, the possible risk of infectious diseases has rendered BC-PS as an unsuitable supplement; however, PS derived from soybean (S-PS) has emerged as a safe alternative (Blokland et al., 1999), To date, few studies have evaluated the actions of S-PS during exercise; consequently, the current study aimed to investigate the effects of S-PS on exercise capacity during intermittent cycling (for example, Fahey and Pearl, 1998). Fourteen healthy young male volunteers, who were matched according to body mass and V O[2max] values, completed this placebo-controlled, double blind supplementation study. Following preliminary assessment and familiarisation sessions, each subject completed two main exercise trials separated by 15+/-1 days. During the ten days prior to undertaking the second main trial the subjects received either 750 mg-day[-1] S-PS or a glucose placebo. During the main exercise trials the subjects completed three 10-min stages of cycling at approximately 45, 55 and 65%V O[2max] (bouts 1-3, respectively) followed by a final exercise bout at 85% VO[2max] (bout 4) that was continued until volitional exhaustion. The exercise bouts were interspaced with 5-min passive rest periods. Breath-by-breath respiratory data (Jaeger Oxycon Pro; Erich Jaeger GmbH, Germany) and heart rate data (Polar S810; Polar electro, Finland) were continually recorded during both main trials. Venous blood samples and the Exercise Induced Feeling Inventory (EFI) (Gauvin and Rejeski, 1993) were collected before exercise (pre-exercise), after each exercise bout and on the day following the main trial. The main finding was that exercise capacity, as indicated by time to exhaustion (TTE) during bout 4, was 25+/-6% longer during trial 2 when compared to trial 1 in PS (P<0.01) while TTE were not significantly different between supplementation groups prior to supplementation (P=0.87). Supplementation had no significant effect on serum cortisol responses during intermittent exercise in either supplementation group. In addition, feeling states (as indicated on the EFI scale) did not differ following supplementation. This is the first study that has evaluated the effects of PS supplementation on exercise capacity. The mechanism(s) by which PS supplementation delayed the onset of fatigue remain unclear. However, it is plausible that PS might have: (1) increased ATPase activity in muscle membrane, and hence maintained ionic balance for longer during exercise and; (2) increased calcium availability in the myofibril, prolonged cross-bridge cycling, therefore delaying fatigue. Further research is warranted to investigate the effects of S-PS supplementation on physiological function and exercise performance.
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