| Abstract: | The aim of this study was to estimate the characteristic exercise intensity
CL which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults maximal oxygen uptake
max 62 (SD 7) ml · min–1 · kg–1] exercisOed for two 30-min periods on a cycle ergometer at 67% (test 1.1) and 82% of
max (test 1.2) separated by 40 min. They exercised 4 days later for 30 min at 82% of
max without prior exercise (test 2). Blood lactate was collected for determination of lactic acid concentration every 5 min and heart rate and O2 uptake
were measured every 30 s. There were no significant differences at the 5th, 10th, 15th, 20th, 25th, or 30th min between
, lactacidaemia, and heart rate during tests 1.2 and 2. Moreover, we compared the exercise intensities
CL which produced the MLSS obtained during tests 1.1 and 1.2 or during tests 1.1 and 2 calculated from differential values of lactic acid blood concentration (1a–]b) between the 30th and the 5th min or between the 20th and the 5th min. There was no significant difference between the different values of
CL 68 (SD 9), 71 (SD 7), 73 (SD 6),71 (SD 11) % of
max (ANOVA test,P<0.05). Four subjects ran for 60 min at their
CL determined from periods performed on the same day (test 1.1 and 1.2) and the difference between the la–]b at 5 min and at 20 min ( (la–]b)) was computed. The la–]b remained constant during exercise and ranged from 2.2 to 6.7 mmol · l–1 mean value equal to 3.9 (SD 1) mmol · l–1]. These data suggest that the
CL protocol did not overestimate the exercise intensity corresponding to the maximal fractional utilization of
max at MLSS. For half of the subjects the
CL was very close to the higher stage (82% of
max where an accumulation of lactate in the blood with time was observed. It can be hypothesized that
CL was very close to the real MLSS considering the level of accuracy of la–]b measurement. This study showed that exercise at only two intensities, performed at 65% and 80% of
max and separated by 40 min of complete rest, can be used to determine the intensity yielding a steady state of la–1]b near the real MLSS workload value. |
