Dietary preparation before rest and exercise testing

To compare the effectiveness of four dietary preparations for stabilizing resting and exercise measurements, seven male recreational exercisers (27 +/- 4 y) participated in four dietary preparations, each repeated in successive weeks: (1) 24-h random diet including an overnight fast (RAN); (2) 24-h random diet, including fast, followed by a standard meal 3 h before testing (RANM); (3) 24-h prescribed diet including an overnight fast (PRES); and (4) 24-h prescribed diet, including fast, followed by a standard meal (PRESM). After each preparation, metabolic rate (VO2) and respiratory exchange ratio (RER) were measured at rest and in association with moderate treadmill exercise. Plasma was analyzed for glucose, cholesterol, and high-density lipoprotein (HDL)-cholesterol. Repeated measures analyses of variance (ANOVAs) followed by Tukey posthoc tests indicated that resting VO2, RER, and blood parameters were not different between the two trials on the same diet. Exercise RER, however, was slightly different in trial 1 than in trial 2 for all preparations except PRESM. Combining both trials, resting VO2 and exercise RER were higher when a pretesting meal was administered. Plasma values were not different for the four dietary preparations. These results suggest that a standard overnight fast appears to be adequate for establishing representative and reproducible rest and exercise values for the parameters measured, except possibly for exercise RER reliability.