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The membrane of erythrocytes contents MCT1 with a low affinity to lactate (La-). Transport of chloride (Cl-) is very fast due to the Hamburger shift. For this reason there should be a mismatch between the distribution of La- and Cl- between the plasma and red blood cells. It has been shown, that La- causes a left shift of the oxygen binding curve (OBC) and Cl- induces a right shift of the OBC. Furthermore the distribution of anions influences fluid shifts and possibly the blood flow regulation. Aim of our study was to determine the alterations in the distribution of these anions and the effects on exercise-relevant physiological systems during high intensive exercise in vivo. Therefore ten male subjects performed a double handgrip wingate-test (2x 30s) with a break of 1 minute. Blood samples were taken before, during and till 30 minutes after the test from a deep cubital vein. We determined [La-]plasma, [La-]ery, [Cl-]Plasma, [Cl-]ery, pH, Hct, MCHC, P50 and COHb. Dircectly after the test the [La-]plasma increased from 1.4 ±0.4 to 14.5 ±3.2mmol/l H2O(p<0.01) (mean ±SD), the [La-]ery increased from 0.7 ±0.4 to 3.6 ±2.2mmol/l H2O (p<0.01). The ratio [La-]ery/[La-]plasma was between 0.5 and 0.2. At the same moment the [Cl-]ery increased from 63.5 ±3.7 to 70.6 ±3.8mmol/l H2O (p<0.01), [COHb] decreased from 1,47 ±0,12 to 0,82 ±0,25% (p<0,01) and the P50 increased from 29,9 ±0,9 to 38.8 ±1.4mmHg (p<0.01). MCHC increased from 33.9 ±0.6 to 34.8 ±0.7 g/dl (p<0.01). The distribution of La- is not according to the DONNAN-equilibrium like the distribution of Cl-. The increase of [Cl-]ery ,caused by the Hamburger shift and the decreasing pH result in a right shift of the OBC, additionally enhanced by decreasing COHb. That possibly effects the BFR because of the desoxyhaemoglobin mediated NO functions. Finally the alterations of distribution of Cl- and of La- in vivo during exercise lead to fast, positive effects on fluid shifts, oxygen supply to the muscle and on BFR.