Work (kg·m per 2minutes) DOSE RESPONSE’S EFFECT ON ENERGY EFFICIENCY SHIFTS IN SEDENTARY OLDER WOMEN FOLLOWING A 16-WEEK TREADMILL WALKING PROTOCOL Joshua R. Sparks, Charity B. Breneman, Ryan R. Porter ,Kimberly P. Bowyer, Sabra Custer, & Xuewen Wang Department of Exercise Science and College of Nursing, University of South Carolina, Columbia, SC RESULTS INTRODUCTION Aging is associated with reduced ability to perform activities of daily living. Aerobic exercise is known to improve cardiorespiratory fitness and cause a potential shift in energy utilization, but little is known regarding changes brought about by exercise training in the capacity to produce work at submaximal levels and whether the dose of exercise affects this production. Work (kg·m per 2minutes) Baseline (BL) Mid-Intervention (MI) End-Intervention (EI) P value: BL-MI MI-EI BL-EI Low Dose (n=16) 487.8 ± 293.1 162.0 ± 65.6 409.3 ± 229.9 <0.001 0.245 High Dose (n=14) 437.5 ± 218.9 294.5 ± 101.5 238.3 ± 152.9 0.045 0.152 PURPOSE To examine the effects of low versus high dose aerobic training programs on amount of work produced at a level individually derived from submaximal V̇O2 in sedentary older women. METHODS ǂ Training: Center-based treadmill walking Constant speed and slope Moderate intensity (50-55%HRR) Low Dose- ~8kcal/kg body weight High Dose- ~14kcal/kg body weight 3 sessions/week for 16 Weeks Outcomes: Mid-Intervention V̇O2 was assessed while walking at a comfortable but challenging speed and grade. Corresponding V̇O2 levels established from Mid-Intervention assessment were located from Baseline and End-Intervention V̇O2Max tests. Work was calculated from Mid-Intervention V̇O2 assessment, as well as at corresponding Baseline and End-Intervention V̇O2 levels. Work (kg·m) = Weight (kg) x Speed (m·sec-1) x Angle of Treadmill Inclination per 2 minutes Participants: Currently sedentary women n = 30 Low Dose (n = 16) Age ± SD = 66.3 ± 4.6 years Weight ± SD= 68.4 ±11.3 kg High Dose (n = 14) Age ± SD = 64.2 ± 2.2 years Weight ± SD = 68.6 ± 9.5 kg Statistics: Repeated Measure ANOVA including (time x dose) Interaction † * * significant difference from BL-MI, ǂ significant difference from MI-EI, † significant difference from BL-EI CONCLUSION Participants exposed to high dose exercise produced less work upon completion of chronic-moderate aerobic training then before training, while those exposed to low dose exercise produced the same amount of work. These results are counterintuitive that, following a high dose aerobic protocol, energy shifts occur to a reduced efficiency state in an older female sedentary population. This work was supported by NIH/NIA R00AG031297