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

The responses of plasma free fatty acids (FFA), free glycerol, beta-hydroxybutyrate (BUT) and glucose to bicycle exercise (corresponding to 50% of the maximal VO2) were investigated in 11 cadets of the Norwegian Military Academy, before a combat course (control experiment) and on the third and fifth 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 with pre-exercise levels before the course. The increases in plasma FFA, glucose and BUT 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). The day 5 responses were lower than those on day 3. The plasma glucose concentration appeared to decrease slightly after exercise on days 3 and 5. The results demonstrate that several days of strenuous work and pronounced energy deficiency do appreciably increase acute metabolic responses to exercise, and indicate that there is a very high FFA-utilization under such conditions.