The difference between net proton release, calculated from the saturation corrected actual base excess (ABEcorr), and lactate release is said to be positive during exercise (Bangsbo et al. 1997). In contrast, we found a negative difference during the exercise bouts (EB) in high intensity intermittent exercise with a small muscle group (10 EB, 15sec/ 45sec break) and a positive one during the break between the EB. In cubital venous blood ph decreased after onset of exercise and reached its minimum (7.16) before the 5th bout (pHven range: 7.16-7.36). After the 2nd EB pHven increased during each EB. Intramuscular pH- measurements under similar conditions (NMR-calf muscle) yielded a pH range of ~6.3 before and ~6.7 after EB. During the 1st and the 2nd EB the arterio-venous difference in [lactate] (AVD_lac) increased whether the AVD_ABEcorr was almost unchanged. However, in the breaks between the 1st and 2nd and between the 2nd and 3rd EB the AVD_lac remained almost unchanged, whether the AVD_ABEcorr became more positive. In the following EB there was only a small difference in the AVD_lac before and after the EB, whether the difference in the AVD_ABEcorr was significantly larger (p<0.001).

This might lead to the suggestion, that H+ is kept in the muscle and lactate leaves the muscle in excess to H+ during the EB of maximum high intensity.