Metabolic responses to bicycle exercise after several days of physical work and energy deficiency

Abstract

The responses of plasma free fatty acids (FFA), free glycerol, .beta.-hydroxybutyrate (BUT) and glucose to bicycle exercise (corresponding to 50% of the maximal .ovrhdot.VO2 [O2 uptake]) were investigated in 11 cadets of the Norwegian Military Academy, before a combat course (control experiment) and on the 3rd and 5th day of such a course which involved nearly continuous intense military activities and pronounced energy deficiency. Pre-exercise levels of FFA, glycerol and BUT were greatly elevated on days 3 and 5 as compared to pre-exercise levels before the course. The increases in plasma FFA, glucose and BUT concentrations in response to bicycle exercise were much more pronounced on days 3 and 5 than before the course. The increases observed during (and before) the course were, approximately, in mmol/l: FFA 1.0 (0.3), glycerol 0.3 (0.08), BUT 0.6 (0.0. Day 5 responses were lower than those on day 3. Plasma glucose concentration appeared to decrease slightly after exercise on days 3 and 5. Several days of strenuous work and pronounced energy deficiency do appreciably increase acute metabolic responses to exercise. There may be a very high FFA utilization under such conditions.