A topical advancement in understanding the control of muscle protein synthesis (MPS) was the discovery of a “Muscle-Full” phenomenon, whereby feeding stimulates only transient increases in MPS, which return to postabsorptive values despite sustained availability of plasma and muscle essential amino acids (EAA) including leucine. We have explored this phenomenon in relation to aging by measuring MPS using a 13C6-phenylalanine stable isotope tracer method. Measurements were made over a 6hr period (2hr fasted and 4hr during / after feeding), using two distinct feeding regimens: 16 older men received either a single 15g mixed EAA feed (N=8, 70±2 y; ‘BOLUS’) or the same dose in 4 x 3.75g fractions at 45 min intervals (N=8, 70±3 y; ‘PULSE’). While MPS was unchanged from fasting in either group 0-90 min after EAA ingestion, it was elevated 90-180 min, irrespective of feeding strategy (BOLUS: 0.051 to 0.084 vs. PULSE: 0.047 to 0.073%/hr). In contrast, while MPS returned to baseline rates in BOLUS between 181-240 min (to 0.052%/hr) this was not the case in PULSE (0.070%/hr, P<0.05 vs. fasting, 2-way RM ANOVA). Despite these temporal differences, equal total MPS responses to feeding regimens were revealed by area under the curve analysis (0.22% vs. 0.23% in 4 h, P>0.05 1-way ANOVA). While equal total MPS between regimens suggests a dose, rather than time-dependent mechanism regulates the muscle-full state in older men, these data point towards sustainment of the anabolic response over longer durations with PULSE feeding regimens.