chapter  8
24 Pages

Protein’s Effects on Rehabilitation and the Sarcopenia of Aging

References .............................................................................................................. 169

sarcopenia based on a skeletal muscle mass index obtained by dividing appendicular skeletal muscle mass (ASM) by body height squared (ASM/ht2) (Janssen et al. 2002). Appendicular skeletal muscle mass is determined by dual energy x-ray absorptiometry (DEXA) scan results. Janssen further divides this into class I and class II sarcopenia. Class I sarcopenia has an ASM/ht2 ratio of –1 to –2 standard deviation of a gender-speciƒc mean value and class II sarcopenia has an ASM/ht2 ratio below –2 standard deviation value (Janssen et al. 2002). Janssen also proposes deƒning sarcopenia by a percentage of skeletal muscle index (SMI%), which is the total muscle mass divided by body mass (Janssen et al. 2000). The accuracy of these measurements may be questionable since sarcopenia is not a uniform condition in the body and DEXA can underestimate body mass index by 20%.