Heterogeneity Within Frailty: Physiological Reserve Phenotypes and Postoperative Recovery After Abdominal Surgery. - Cudnik, Rafał; Marano, Luigi; Montanari, Elena; Marano, Alessandra; Semeraro, Eugenia; Santarelli, Mauro; Cwalinski, Tomasz; Girnyi, Sergii; Fimognari, Filippo Luca; Boccardi, Virginia (Journal of Clinical Medicine, 2026)