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MLSS DOES NOT CORRESPOND TO THE MAXIMAL RATE OF LACTATE ELIMINATION |
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Sassi Aldo, Impellizzeri Franco M, Rampinini Ermanno
The aim of this study was to verify if, according to different theories, above the maximal lactate steady state (MLSS), lactate elimination cannot be further significantly increased to such an extend to overcome the formation rate.
Six male cyclists of recreational level (VO2max 61 „b 11 ml/kg/min; weight 69 „b 1 kg; height 174 „b 6 cm; age 36 „b 6 yrs) were involved in the study.
MLSS was defined as the maximal intensity at which blood lactate does not increase more than 1 mmol/l from min 10 to min 30 of a steady state exercise. In order to find, by trial and errors, an individual workload slightly higher than MLSS (HMLSS), in separate occasions (every 3-4 days), the subjects were submitted to steady state workouts on a SRM ergometer (SRM, Welldorf, Germany). In the first 5 min of a following workout, 50 W were overimposed to the individual HMLSS (50HMLSS), in order to cause an early lactate accumulation over MLSS workout corresponding value; then, from min 5 to min 30, power output was reduced to the individual HMLSS: a relative lactate decrease after the reduction of the power output to HMLSS, should be inconsistent with the assumptions that over MLSS, lactate utilisation cannot be further significantly increased.
To compare blood lactate values of the two trials Student t-test for paired data was used. Results show that at the individual HMLSS lactate increases from min 10 to min 30 was of 1,28+0,20 mmol/l (range: 1,06 - 1,53 mmol/l), supporting the overcoming of the MLSS. In 50HMLSS exercise, at min 5 blood lactate was higher than HMLSS at min 5 (7,08+1,87 mmol/l vs. 3,53+1,10 mmol/l; p<0,002). From min 8 of exercise, a lactate decrease takes place (with the characteristic exponential shape of lactate disappearance), resulting in a trend towards difference against HMLSS at min 15 (5,24+1,75 mmol/l vs. 4,17+1,24 mmol/l; p=0.056), and reaching the same HMLSS average value at min 25 (5,13+1,60 mmol/l vs. 4,88+1,31 mmol/l).
Results of this study show that even at metabolic intensities slightly above MLSS, lactate removal can be increased to an extend enough to overcome lactate production; that is the case in presence of lactate levels previously increased above the corresponding MLSS individual values. As a consequence, MLSS does not correspond to an absolute ceiling or maximal rate of lactate elimination: these generally accepted limitations must be intended only related to lactate concentrations typical of MLSS conditions in different body compartments. |
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