Lipoprotein concentrations are well established biological markers associated with cardiovascular disease (CVD) risk. Recent research has placed great importance on the function of different lipoprotein subfractions (medium and small VLDL; small and large LDL; small, medium and large HDL). Current literature supports exercise as being protective by affecting lipoprotein particle size and concentration, whereas little research has been conducted to determine the effects of exercise dose on these outcomes. PURPOSE: To determine if exercise dose has an effect on VLDL, LDL, and HDL particle size and concentrations in older sedentary women after 16 weeks of moderate-intensity aerobic exercise. METHODS: Sixty-five women (age = 64.7 + 4.2 years) were randomized into higher-dose (n = 30) and lower-dose (n = 35) exercise groups. Supervised treadmill walking sessions lasted approximately 35 or 55 minutes, 3 times per week, for lower-dose and higher-dose groups, respectively. All exercise was completed at an intensity of 50-55% of heart rate reserve. Fasting plasma samples were collected before and after exercise intervention. Plasma lipoprotein particle concentrations and average sizes were determined by nuclear magnetic resonance spectroscopy. RESULTS: Exercise, in the entire sample, lowered total HDL and small VLDL particle concentration (1.5 ± 3.6 μmol/L and 4.2 ± 16.4 nmol/L; p<0.01 and p<0.05, respectively), and increased mean HDL particle size (0.1 ± 0.3 nm; p<0.01). When analyzed by exercise groups, the lower-dose group displayed a decrease in total HDL particle concentration (1.9 ± 3.1 μmol/L; p=0.001), while the higher-dose group displayed an increase in mean LDL particle size (0.3 ± 0.5 nm; p<0.05). Both exercise higher-dose and lower-dose treatments were found to significantly increase mean HDL particle size (0.1 ± 0.2 nm and 0.1 ± 0.3 nm, respectively; p<0.05) with no significant difference between groups. CONCLUSIONS: The results from this study support that exercise in sedentary older women decreased CVD risk. Though the HDL particle concentration decreased in the lower- dose group, maintenance of HDL particle concentration in the higher-dose group along with the increase in mean HDL and LDL size are characteristics associated with lower CVD risk. Supported by NIH Grant R00AG031297