Acta Astronautica Vo1.27, pp. 61 - 64, 1992 0094-5765/92 $5.00+0.00 Printed in Great Britain Pergamon Press Ltd BLOOD LACTATE DURING LEG EXERCISE IN MICROGP, AVlTY P. Zamparo, C. Capelll and G. Antonutto Institute of Biology, School of Medicine, Via Gervasutta 48, 33100, Udlne, Italy ABSTRACT. Venous blood lactate concentration ([La]b) was measured In five male subjects (age: 30-50 years; BW: 72-84 kg, ~to2max:2.2-3.6 I ,rain -1) during cycloergometrlc exercise in mlcrogravlty oblained by parabolic fUgth maneuvers of -25 s duration. The subject(s) exercised at 30, 60, 90 and 120 W (60 RPM) for at least 7 rain at oach Intensity. Three consecutive parabolas wllh ~ 3 rain Interval were performed at each workload. [La]bwaS determined at rest and Immediately after 60, 90 and 120 W exercise. The day after the flight experiments, the subject(s) underwent the same experimental protocol on the ground and the blood samples were taken at the very same time Intervals as on the aircraft. [La]b In flight and control didn't show any appreciable difference once the values are plotted as a function of the relative exercise Intensities expressed as a percent of the Individual ~O2 max corrected for the moderate hypoxla prevailing Inside the aircraft (cabin barometric pressure = 590 mmHg). Keywords:exercise,microgravity, parabolicfligth, blood lactate. INTRODUCTION As previously shown (2), during constant load cyclo-ergometrlc exercise of moderate Intensity (80 W) performed In microgravlty (l~g), the 02 uptake Is reduced as compared to normal 1 g conditions. Indeed, the overall 02 taken up during a complete parabolic maneuver of ~ 60 s, Including the pre - and post - parabolic hypergravity (-1.8 g) periods (15- 20 s), was significantly less than during an equal period of time at the same exercise level, but at I g. Even though an effect of ~g on the blomechenlcs of cycling could not be ruled out, the reduction of 02 utigzatlon over the entire parabola may suggest that the working muscles were partly resyntheslzlng ATP via anaerobic glycollsis. Indeed, the conspicuous pooling of blood In the upper part of the body resulting from the dlsappoarance of the head to feet gz vector during pg, may well Impair the oxygen supply to the working muscles of the lower limb, thus speeding UP the lactate production. If the overall energy requirement remains constant, the energy provided by the glycolltic anaerobic pathway will rewttl Itself as a reduction of the pulmonary oxygen consumption. The aim of the present Investigation was to assess whether, during cycloergometrlc exercise of moderate intensity performed during parabolic maneuvers, them is Indeed a substantial accumulation of La in blood in comparison with control experiments performed on the ground. METHODS EXDeflmental Drotocol The flight experiments were performed after take off from the Br~igny sur Orge airfield, Ivry, France, on a Caravelie aircraft oberated by the CNESICEV. The control ground experlments were performed the following day on the same subjects who had flown the day before. Five male subjects participated in the experiments (their main physiological and anthropometrlc characteristics are shown In Table 1). Su~e~ Age Bw VO2max (yeare) (kg) (I • rain -1) P.P. 50 72 2.6 V.P. 35 84 3.6 A.K. 31 79 3.2 C.C. 30 75 2.4 G.A. 41 72 2.2 61 Tab. 1. Anthropometdcaland physiological characteristics of the subjects.