The Effect of Acute Exercise upon Postprandial Lipemia Following Correction for Plasma Volume Shifts

Abstract

1489 PURPOSE: To examine the influence of plasma volume (PV) adjustments on our previously reported finding that isocaloric bouts of acute strength (ST) and aerobic training (AT) had no effect on fasting and postprandial plasma lipoprotein concentrations in 13 healthy normolipidemic males (age, 20.9 ± 0.6 years). METHODS: Subjects participated in three postprandial lipemia tests, one control (CON) and the other two 14-hours following isocaloric bouts of ST and AT. During all 3 tests, venous samples were obtained in a 12-hr fasted state and after the consumption of a high fat breakfast (55 g fat, 149 g carbohydrate, 22 g protein). Blood samples were analyzed for plasma triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and glucose. Changes in PV were determined using the fasting CON trial hematocrit (Hct) and hemoglobin (Hb) values as the reference point from which all blood samples from the CON trial and exercise trials were compared. TG was monitored hourly for 6 hours from which the incremental (INCAUC) and total (TOTAUC) areas under the 6-hour TG curve were calculated. Differences between CON, ST and AT trials, with and without PV corrections. RESULTS: Hb was significantly higher in the fasting AT blood sample compared to the fasting CON sample (CON, 11.48 ± 0.78; AT, 14.13 ± 0.65; ST, 13.46 ± 0.53 mg/dl). The AT and ST fasting blood samples displayed 18 and 14 % reductions in PV, respectively. After PV correction there was no effect on fasting plasma TG or HDL-C concentrations. However, fasting plasma TC (CON, 172.5 ± 7.3; AT 138.1 ± 7.5; ST 149.2 ± 8.2 mg/dl) and glucose (CON, 85.9 ± 1.7 AT 70.8 ± 1.5; ST 69.6 ± 1.6 mg/dl) were significantly lower (P<0.05) following both exercise bouts. The 6-hour plasma TG INCAUC (CON, 355.0 ± 60.4; ST 183.5 ± 36.6; AT, 130.3 ± 30.1 mg/dl × 6h) and glucose TOTAUC (CON, 531.6 ± 19.8; ST 432.4 ± 20.1; AT, 419.8 ± 23.2 mg/dl × 6h) were significantly reduced during both exercise trials. CONCLUSION: These data suggest that PV corrections over multiple tests may provide a clearer picture of the effect of exercise treatments upon PPL. Given uncertainty over the exact cause of post exercise PV shifts and the large PV variation between trials in this study it is suggested that fluid and salt intakes be controlled during the 24-hours preceding fat tolerance tests.