Rationale for a preliminary operational definition 314of physical frailty and sarcopenia in the SPRINTT trial

In the present article, the rationale that guided the operationalization of the theoretical concept of physical frailty and sarcopenia (PF&S), the condition of interest for the "Sarcopenia and Physical Frailty in Older People: Multicomponent Treatment Strategies" (SPRINTT) trial, is presented. In particular, the decisions lead to the choice of the adopted instruments, and the reasons for setting the relevant thresholds are explained. In SPRINTT, the concept of physical frailty is translated with a Short Physical Performance Battery score of ≥3 and ≤9. Concurrently, sarcopenia is defined according to the recent definitions of low muscle mass proposed by the Foundation for the National Institutes of Health-Sarcopenia Project. Given the preventive purpose of SPRINTT, older persons with mobility disability (operationalized as incapacity to complete a 400-m walk test within 15 min; primary outcome of the trial) at the baseline are not included within the diagnostic spectrum of PF&S.