Fractional mixed muscle protein synthesis rates (FSR), calculated using plasma L-[<i>ring</i>-²H₅] phenylalanine enrichments as the precursor pool, in healthy young and elderly men in the post-absorptive state (<i>n</i> = 34 young and <i>n</i> = 72 elderly) and following the ingestion of 20 g protein (post-prandial; <i>n</i> = 35 young and <i>n</i> = 40 elderly.

<p>Delta increases from post-absorptive to post-prandial were analyzed between groups using an unpaired <i>t</i>-test (significantly different; <i>P</i><0.01). Individual responses are reported in the inset figure only in those subjects for whom post-absorptive and post-prandial muscle protein synthesis rates were assessed within the same experiment (<i>n</i> = 55 [22 young and 23 elderly]).