The present investigation examined the effects of hyperglycemia throughout prolonged intense exercise on hormonal responses. Eight male subjects undertook
two trials during which they exercised on a cycle-ergometer at an intensity of 70%
VO2max for 120 min. In the first trail (Trial A), subjects had their blood glucose concentration clamped at 12 mmol/l 30 min before exercise and throughout exercise. The same rate and volume of infusion of 0.9% saline as had occurred for
trial A were used in a placebo trial (trial B).
Plasma lactate concentrations were elevated during exercise in both trials
(P
saline infusion (P<0.05). Glucose infusion and maintained hyperglycemia resulted
in significantly lowered plasma concentrations of NEF A, glycerol, epinephrine, norepinephrine, and GH (P
plasma insulin were significantly elevated (P
These data suggest that glucose infusion and maintained hyperglycemia
during prolonged intense exercise prevent the hormonal responses to exercise,
which are responsible for hepatic glucose release and muscle glycognolysis.
)