Rate of Force Development is Related to Maximal Force, Muscle Quality and Physical Function in Patients With Chronic Kidney Disease Predialysis

ABSTRACT Background Physical function is severely compromised in people with chronic kidney disease (CKD) and worsens with continued decreases in kidney function. Neuromuscular force capacity is a key determinant of physical function in healthy older adults, though its importance in persons with CKD is less understood. Methods This study aimed to determine the relationships among rate of force development (RFD), muscle quality and physical function in a group of community-dwelling, middle-aged and older men (n=14; age=71.2+/-6.2 years) with CKD stages 3 and 4 (eGFR=37.5+/-10.4 ml/min per 1.73 m2). Force characteristics were determined from maximal knee extensor isometric contractions and muscle quality was estimated using ultrasound grayscale analysis. Physical function was assessed by the Short Physical Performance Battery (SPPB) and 5-repetition sit-to-stand (STS) test. Results eGFR was directly related to SPPB (r=0.54, p=0.044) and inversely related to STS (r=-0.62, p=0.029). RFD was positively related to SPPB at time points 0-50 ms, 50-100 ms, and 0-300 ms (RFD0-50, r=0.73, p=0.010; RFD50-100, r=0.67, p=0.022 and RFD0-300 r=0.61, p=0.045); and inversely related to STS at time points 0-50 ms, 50-100 ms, and 0-300 ms (RFD0-50, r=-0.78, p=0.007; RFD50-100, r=-0.78, p=0.006 and RFD0-300 r=-0.76, p=0.009), respectively. RFD was positively associated with maximal voluntary force (MVF) at times 50-100 ms, 100-200 ms, and 0-300 ms (RFD50-100, r=0.72, p=0.011; RFD100-200, r=0.66, p=0.025; and RFD0-300 r=0.70, p=0.016), respectively. Neither MVF nor muscle quality was significantly associated with functional measures. Conclusions RFD is an important determinant of physical function in middle-aged and older men with CKD stages 3 and 4.