An improved lactate transport across the red blood cell membrane might be an advantage during high intensity exercise by increasing the muscle-to-plasma [La] gradient and therefore allowing more lactate/H+ to leave the muscle. It is hypothised that the bioavailability of MCT (Monocarboxylattransporter) may be altered by translocation from cytoplasm to the membrane of RBC when it is needed. Therefore we investigated if lactate transport across RBC membrane can functionally be influenced after maximal exercise by previous different warming up protocols (WU). Methods: At three subsequent visits to the laboratory, subjects performed 30 s lasting maximal sprint tests on a cycle ergometer with different prior warm up intensities: 1. without prior warming up (W), 2. extensive warm up (E): 12 min cycling at 60% of VO2 peak, 3. intensive warm up (I): 12 min cycling at 60% of VO2 peak including three 10 s lasting peaks at 200% of VO2 peak. After warming up, subjects stayed in a sedentary position for 5 min followed by the maximal sprint test. Blood samples were taken under resting conditions, after warming up, before sprint exercise (pre M) and in minute intervals during recovery (0 min-15 min) to determine lactate concentrations in whole blood, plasma and RBC. Results: The initial increments (pre M-0`) in plasma & RBC [La] showed significant differences between W/E and I. The RBC/plasma [La] ratio of the increments (pre M-0`) was significantly lower for I (0.23 ± 0.06) compared to W & E (W: 0.28 ± 0.04 & E: 0.27 ± 0.04). These differences were due to lower increments in RBC [La] (-16% W vs. I & -10% E vs. I). No significant differences were found for the increments of plasma, RBC & ratio in the following time intervals. The peak power (PP) output as well as the mean power (MP) output for the sprint test was significantly lower for W (MP: 680 ± 181 Watt) compared to E & I (MP: 738 ± 192 Watt; E) (MP: 740 ± 191 Watt; I). Discussion: Several possible effects of WU are discussed in literature which might have an effect on performance. In the present study we tested if different warming up intensities influence the lactate flux across the RBC membrane. A recent study from our group has shown that MCT in RBC might be translocated from cytoplasm to the membrane in response to exercise, which might effect La flux. In the present study the WU had no influence on La flux across the RBC membrane. The increase in plasma [La] was significantly lower in the first time interval for "I". Therefore one would expect a similar or even higher increase in RBC [La] (and not a lower) because of a less stressed transport system. But may be it must be considered, that the pre-loading of RBC with lactate and therefore the [La] gradient is different between the conditions. It can be speculated, that the time (of warming up) was too short to induce a translocation of MCT. Further molecular investigations are needed to identify possible mechanisms for translocation of MCT.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Veröffentlicht von The Norwegian School of Sport Sciences. Alle Rechte vorbehalten.