Plasma catecholamine and blood lactate cumulation during incremental exhaustive exercise

Six healthy male subjects performed two different incremental treadmill tests. Test 1 started at a velocity of 8 km.h-1 and was increased by 2 km.h-1 steps until subjective exhaustion was reached. The running time was 3 min per step with 30-s interruptions between two successive steps. In test 2, identical work loads were imposed on the subjects. However, there were 30-min recovery periods between two successive exercise steps. Heart rate, oxygen uptake (only in test 1), blood lactate, and free plasma catecholamine levels were simultaneously estimated during both testings and additionally at the end of each 30-min recovery period in test 2. Subjects reached 57 +/- 6 ml.kg-1. min-1 oxygen uptake. Only slight lactate and catecholamine differences were observed between both tests at moderate work loads. Lactate levels (+30%) as well as noradrenaline and adrenaline responses (+60%-90%) were higher in the cumulative experiment (test 1) at work loads corresponding to 70%-80% of the oxygen uptake capacity as compared to the noncumulative testing procedure (test 2). A further increase of these differences to approximately 50% (lactate), 156% (noradrenaline), and 165% (adrenaline) has to be considered to be near the exhaustion level. In conclusion, during incremental treadmill exercise in a cumulative design, a significant cumulation effect leads to an overproportional increase of lactate and catecholamine levels at submaximal--maximal work loads.