Fig. 5. Direct assessments of whole-body functional muscle mass using D3-Cr dilution method. A small dose of absorbed D3-Cr and endogenous Cr in the skeletal muscle will irreversibly be converted to Crn. The Crn enrichment from urine reflects the dilution of D3-Cr as a function of the abundance of existing creatine pool. Knowledge of 1) whole-body Cr pool size (determined) and 2) muscle Cr concentrations (known to be constant) enables calculations of skeletal muscle mass. For a given D3-Cr oral consumption, a greater dilution of D3-Cr will occur in cases of large muscle mass (a) compared with smaller muscle mass (b). This figure was created with BioRender.com.
Cr = creatine; Crn = creatinine.
© 2022 Ann Clin Nutr Metab
