Effects of long distance running at high altitude on the standard oxygen-hemoglobin dissociation curve and red cell 2,3-DPG

Abstract

The relationship of high altitude running performance to hemoglobin-oxygen affinity and red cell 2,3-diphosphoglycerate (2,3-DPG) was evaluated in nine experienced marathon runners participating in a 46-km run over a mountain, at altitudes of 1,950 m–3,400 m. The runners were acclimated to 1,600 m altitude. Venous blood was donated before the run, and at 5, 23, and 46 km distance and elevations of 2,400, 3,400, and 1,950 m, respectively. The mean standard (std) P50 increased from 3.33 kPa±0.04 SEM (25.0 mm Hg±0.3) to 3.63 kPa±0.04 (27.2 mm Hg±0.3) (p<0.05) during the run. These changes in std P50 values cannot be attributed to changes in 2,3-DPG levels, as the latter were not changed at 5 km, and were decreased (from 4.71±0.12 to 3.88±0.26 Μmol·ml−1 packed cells) at 23 km (p<0.05), with no further change at 46 km. The faster runners exhibited a larger right-shifting of the oxyhemoglobin dissociation curve, and the greater increase in its central slope. The time needed to finish the run correlated directly with the decrease in hemoglobin-oxygen affinity at 23 and 46 km (p<0.05). The observation that a decreased hemoglobin-oxygen affinity is correlated with a better running performance suggests that under the progressively hypoxic conditions of this run, myocardial oxygenation and cardiac output might have been improved by an increase in P50 attributable to increased body temperature, decreased blood pH, and an increase in std P50.