Effects of phosphate loading on 2,3-diphosphoglycerate and maximal oxygen uptake

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Abstract
Increased concentration of red blood cell 2,3-diphosphoglycerate (RBC 2,3-DPG) shifts the Hb-O2 dissociation curve to the right, thus theoretically allowing better oxygenation of tissues. The effects of oral phosphate loading on several parameters including plasma phosphate concentration, RBC 2,3-DPG, hematocrit and Hb concentration, maximal O2 uptake (.ovrhdot.VO2 max) and degree of lactic acidemia was investigated in 10 well-trained distance runners. After control determinations were made, either a phosphate load or a placebo was given for 3 d [day] before the athlete was restudied. A placebo and 2 phosphate-loading studies were performed at weekly intervals, followed by 2 wk of rest and another post-intervention control study. Blood samples for control values were drawn before and after a standard warm-up period, after treadmill exercise at a 10% grade and at the completion of the .ovrhdot.VO2 determination. After oral phosphate loading there was a significant increase in serum phosphate and RBC 2,3-DPG. Maximal O2 uptake was significantly increased and correlated with the rise in RBC 2,3-DPG (r = 0.81). The increase in blood lactate after exercise on the 10% grade was attenuated during sessions which followed phosphate loading.