We address (i) the epidemiology and clinical significance of cardiorenal overlap across CRS/CKM, (ii) functional phenotypes defined by inactivity, low exercise capacity, sarcopenia/frailty, and disability, (iii) rehabilitation effects on physical function and renal trajectories, including renal endpoint validity (creatinine vs. cystatin C), and (iv) prognostic implications and evidence gaps. Here, CST3 is linked to sarcopenia.