Metabolism during and after Exercise

 

George A. Brooks and Gregory C. Henderson

University of California, Berkeley

 

To examine how glycemia is defended in healthy men and women during and after exercise bouts requiring substantial energy expenditure we determined rates of glucose appearance (Ra), disappearance (Rd), and metabolic clearance (MCR) before, during and after isoenergetic moderate and hard intensity exercise.  As well, we determined the extent to which lipolysis an FFA mobilization and oxidation participated in supporting the challenge to glycemia.  On separate days, 10 men and 8 women received primed-continuous infusion of [6,6-²H₂]glucose to measure glucose kinetics, [1,1,2,3,3-²H₅]glycerol and [1-¹³C]palmitate to measure glycerol and plasma FA kinetics, or NaH¹³CO₃ to assess ¹³CO₂ retention.  Participants were studied under 3 different conditions with diet unchanged between trials: 1) before, during and 3 h after 90 min of exercise at 45% VO₂peak (E45), 2) before, during and 3 h after 60 min of exercise at 65% VO₂peak (E65), and 3) in a time-matched sedentary control trial (C).  In men and women the increase in CHO oxidation scaled to exercise intensity, but was greater in men.  Blood [glucose] was depressed below C during recovery in men, but not women. In contrast, during 3 h of post-exercise recovery, glycerol Ra remained elevated in men, but not women.  FA Ra increased during exercise in both sexes and was higher during E45 than E65. The relative increase in FA Ra during 3 h of post-exercise recovery was greater in men than women.  Plasma FA oxidation (RoxFFA) increased during exercise with no difference between intensities, and RoxFFA remained elevated during 3 h of post-exercise recovery in both sexes   After exercise total lipid oxidation (Lox) was elevated in both sexes, but more in men, after both 3- and 22 hr of recovery. Following exercise bouts, women are better able to maintain glycemia, thus not requiring the counter-regulation of glucose production that is seen in men and requiring less augmentation of lipid metabolism.

 

Key words: Exercise, Recovery, Glucose Homeostasis, Lipid Oxidation, Gender