Baseline Physiological Reserve Provides Greater Explanatory Value Than Discharge-Attained Strength Change for Early Postoperative Outcomes After Elective Abdominal Surgery

Background Acute perioperative handgrip strength change measured at discharge (Δacute) is often interpreted as a marker of vulnerability. However, it is discharge-anchored, influenced by peri-discharge conditions, and not measured at a standardized postoperative timepoint. We examined whether Δacute was independently associated with prolonged length of stay (LOS) after elective abdominal surgery once baseline physiological reserve was considered.Methods Adults undergoing elective abdominal surgery were prospectively enrolled in a multicenter observational cohort. Handgrip strength (HGS) was assessed at admission and discharge, and frailty using the Fried phenotype. Δacute was defined as discharge minus admission HGS. The primary outcome was LOS >10 days. Associations were examined using correlation and multivariable logistic regression, with sensitivity analyses addressing extreme values and non-normal distributions.Results Among 223 patients (median age, 65 years), 48 (21.5%) had prolonged LOS. Frailty status (OR 2.63, 95% CI 1.47–4.70) and oncologic surgery were independently associated with prolonged LOS, whereas admission HGS was not significant after adjustment. Δacute showed substantial interindividual variability, correlated inversely with admission HGS (r = −0.325, p < 0.001), and differed by surgical context, but was not associated with prolonged LOS in univariable or multivariable analyses.Conclusions Discharge-anchored Δacute was not independently associated with prolonged LOS after accounting for baseline reserve and surgical context. Because both Δacute and LOS may be influenced by discharge timing and institutional practices, these findings do not establish that acute strength change reflects postoperative perturbation rather than intrinsic vulnerability.