Introduction: 

An improved lactate transport across the RBC 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 MCT1 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): 12min 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 the warming up, subjects stayed in a sedentary position on the cycle ergometer for 5min. Afterwards subjects performed the maximal sprint test. Blood samples were taken under resting conditions, directly after warming up, 1min before sprint exercise (pre M), directly after sprint exercise (0') and in minute intervals during recovery (15 min) to determine lactate concentrations in whole blood, plasma and erythrocytes.

Results: 

The peak power (PP) output as well as the mean power (MP) output for the sprint test was significantly lower for W (PP: 951 91 W & MP: 680 181 W) compared to E & I (PP: 1007 110 W & MP: 738 192 W; E) (PP: 1022 90 W & MP: 740 191 W; I). 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 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) compared to plasma [La]. No significant differences for the increments of plasma, RBC & ratio were found in the following time intervals.

Discussion: Several possible effects of WU (systemic/local) are discussed in literature which might have an effect on performance. In this case we tested if different warming up intensities influence performance and the lactate 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 into RBC (and no a lower like in the present study) because of a less stressed transport system compared to higher increases. But may be it must be considered that the pre-loading of RBC with lactate is different between the conditions. Another important factor might be the concentration gradients between both compartments. Further molecular investigations are needed to identify a possible translocation of MCT.