G. Brisson

Blood pressure and plasma catecholamine responses to various challenges during exercise-recovery in man

SummaryThe purpose of this study was to assess the effects of a 2 h cycle exercise (50%

Comparison of two methods for computing exogenous substrate oxidation using 13C-labeling

\dot V_{O_2 \max }

SUBSTRATE UTILIZATION AND INSULIN RESPONSE TO GLUCOSE AND FRUCTOSE INGESTION DURING EXERCISE IN MAN

) on heart rate (HR) and blood pressure (BP), and on plasma epinephrine (E) and norepinephrine (NE) concentrations, during the recovery period in seven normotensive subjects. Measurements were made at rest in supine (20 min) and standing (10 min) positions, during isometric exercise (hand-grip, 3 min, 25% maximal voluntary, contraction), in response to a mild psychosocial challenge (Stroop conflicting color word task) and during a 5-min period of light exercise (42±3%

Oxidation rate of four types of carbohydrates ingested 30 min before a period of prolonged exercise at moderate intensity in healthy male subjects.

\dot V_{O_2 \max }

310 EXOGENOUS 13C-LIPIDS AND 13C-GLUCOSE OXIDIZED DURING PROLONGED EXERCISE IN HAN: A COMPARISON STUDY

). Data were compared to measurements taken on another occasion under similar experimental conditions, without a previous exercise bout (control). The results showed HR to be slightly elevated in all conditions following the exercise bout. However, diastolic and systolic BP during the recovery period following exercise were not significantly different from the values observed in the control situation. Plasma NE concentrations in supine position and in response to the various physiological and/or psychosocial challenges were similar in the control situation and during the recovery period following exercise. On the other hand plasma E (nmol · l−1) was about 50% lower at rest (0.11±0.03 vs 0.23±0.04) as well as in response to hand-grip (0.21±0.04 vs 0.41±0.20) and the Stroop-test (0.21±0.05 vs 0.41±0.15) following the exercise bout. This reduction might reflect changes in plasma epinephrine removal accross the forearm due to changes in blood flow. However, it might also indicate a reduction in the activity of the adrenal medulla which might have some implications in the use of regular exercise in the control of BP in hyperadrenergic hypertensive subjects.

562: BLOOD PRESSURE AND PLASMA CA AT REST AND IN RESPONSE TO VARIOUS CHALLENGES DURING RECOVERY FROM EXERCISE

The purpose of this study was to reassess the metabolic availability of oral glucose during prolonged exercise in man, using 13C-labeling and a computation procedure (J Appl Physiol 69:1047-1052, 1990) that correctly takes into account changes in isotopic composition of CO2 arising from oxidation of endogenous substrates (Rendo). These changes are due to glucose ingestion associated with exercise. Each of the seven subjects completed three 2-hour periods of exercise at 67% maximum oxygen consumption (VO2max) on an ergocycle, with ingestion of water (1,000 mL) or 60 g (in 1,000 mL water) of 13C-labeled glucose at two levels of enrichment (13C/12C = 1.11482% and 1.13303%). As expected, Rendo significantly increased from rest to exercise with water ingestion (1.09888% +/- .00196% to 1.09970% +/- .00175%) and with glucose ingestion (1.10002% +/- .00159%) due to changes in the respective contributions of endogenous carbohydrates and fat to energy requirements as assessed by the respiratory exchange ratio (RER). When changes in Rendo were taken into account, the estimated amount of exogenous glucose oxidized was 38.8 +/- 10.3 g. Much higher values were found when Rendo at rest or during exercise with water ingestion were used in the computation (42.3 +/- 10.3 to 65.1 +/- 20.5 g) according to the commonly used method. Examination of data in the literature indicates that the reported oxidation rate of exogenous glucose (g/min) is significantly related to oxygen consumption (VO2) (L/min; r = .592) and that exogenous glucose contributes approximately 14% to 17% to the energy requirement.(ABSTRACT TRUNCATED AT 250 WORDS)