Effects and post-effects of two-hour exhausting exercise on composition and gas transport functions of blood

Eleven male sport students (age 23.3 +/- 1.7 years) exercised for 2 h on a bicycle ergometer (60 rpm), the braking force of which was regulated to yield a constant pulse rate (156 +/- 3 min-1). Before, at end of, and 3 and 6 h after exercise blood was sampled from a cubital vein and an earlobe for measurement of hemoglobin (Hb) concentration, hematocrit (Hct) value, osmolality (Osm), plasma protein (Prot), sodium (Na+), potassium (K+), inorganic phosphate (Pi), and lactate (Lac) concentrations, red cell 2,3-diphosphoglycerate (DPG) and adenosin triphosphate (ATP) concentrations, acid base status and half saturation pressure (P50) of the oxygen dissociation curve. At end of exercise [Hb], Hct, [Prot], Osm, [K+], [Pi] and [Lac] were significantly elevated, pH in ear lobe (+ 0.04) and venous blood (+ 0.08) was also increased by both respiratory and nonrespiratory effects (BE + 1.4 mmol/l). The oxygen dissociation curve showed an unexplained slight right shift (standard P50 + 0.19 kPa). During the post-exercise period most parameters approximated to control values after only 3 h. [Prot] and especially [Pi], however, remained elevated while [DPG] slightly rose during the post-exercise period. It is suggested that these changes are first signs of adaptation to exercise, perhaps caused by endocrine stimulation.