METABOLIC AND HORMONAL RESPONSES DURING REPEATED BOUTS OF BRIEF AND INTENSE EXERCISE - EFFECTS OF PREEXERCISE GLUCOSE-INGESTION

We investigated metabolic and hormonal responses during repeated bouts of brief and intense exercise (a force-velocity test; Fv test) and ex amined the effect of glucose ingestion on these responses and on exerc ise performance. The test was performed twice by seven subjects [27 (2 ) years] according to a double-blind randomized crossover protocol. Du ring the experimental trial (GLU), the subjects ingested 500 mi of glu cose polymer solution containing 25 g glucose 15 min before starting t he exercise. During the control trial (CON), the subjects received an equal volume of sweet placebo (aspartame). Exercise performance was as sessed by calculating peak anaerobic power ((W) over dot (an,peak)). V enous plasma lactate concentration increased significantly during the Fv test (P < 0.001), but no difference was found between CON and GLU. Blood glucose first decreased significantly from the beginning of exer cise up to the 6-kg load (P < 0.001) and then increased significantly at (W) over dot (an,peak) and for up to 10 min during the recovery per iod (P < 0.001) in both CON and GLU. Insulin concentrations decreased significantly in both groups, but were higher at (W) over dot (an,peak ) in GLU compared with CON (P < 0.05). Glucagon and epinephrine did no t change significantly in either group, but epinephrine was significan tly lower in GLU after glucose ingestion (P < 0.05) and at (W) over do t (an,peak) (P < 0.05) (W) over dot (an,peak) was not significantly di fferent between CON and GLU. In conclusion, blood glucose and insulin concentrations decreased during repeated bouts of brief and intense ex ercise, while blood lactate concentration increased markedly without a ny significant change in glucagon and epinephrine concentrations. Gluc ose ingestion altered metabolic and hormonal responses during the Fv t est, but the performance as measured by (W) over dot (an,peak) was not changed.