Combined Flywheel Resistance and Aerobic Exercise on Power output and Function in Chronic Kidney Disease: An Exploratory Study on the Influence of Physical Activity

New FindingsWhat is the central question of this study? Are adaptations elicited by combined flywheel resistance and aerobic exercise influenced by habitual physical activity levels in patients with chronic kidney disease? What is the main finding and its importance? Combined flywheel resistance and aerobic exercise promote clinically meaningful improvements in muscle size, power output, and physical function in patients with chronic kidney disease. Those not meeting the weekly moderate intensity physical activity recommendations experienced greater increases in power output compared to those who were physically active whereas no differences in the magnitude of improvements in physical function were observed between physical activity levels. Physical inactivity is common in chronic kidney disease (CKD) and is associated with poor neuromuscular and functional outcomes. Whether habitual physical activity (PA) influences adaptations to structured exercise in CKD remains unclear. This study examined if adaptations to combined flywheel resistance and aerobic exercise (FRE+AE) differed based on self-reported PA in Veterans with CKD stages 3-4. Twenty older male Veterans with CKD stages 3-4 (mean eGFR 37.9 {+/-} 10.2 mL/min/1.73 m{superscript 2}) were randomized to six weeks of FRE+AE (n=11) or health education (EDU; n=9). Participants were classified as meeting (Meets PA) or below (Low PA) weekly moderate intensity PA recommendations using the 7-day Physical Activity Recall. Outcomes included vastus lateralis muscle thickness (VL MT), knee extensor power output (60{degrees}{middle dot}s-1 and 180{degrees}{middle dot}s-1), gait speed (GS), and five-repetition sit-to-stand (STS). FRE+AE increased VL MT (p=0.030), power output at 180{degrees}/s (p=0.021), GS (p=0.001), and reduced STS time (p=0.012), with significant between-group differences versus EDU for VL MT (p=0.009) and GS (p=0.028). Low PA experienced greater increases in power output at 60{degrees}{middle dot}s-1 (Hedges g; Low PA=0.44, Meets PA=0.25) and 180{degrees}{middle dot}s-1 (Hedges g; Low PA=1.38, Meets PA=0.38) compared to Meets PA after FRE+AE. Conversely, Meets PA had greater improvements in GS (Hedges g; Low PA=0.93, Meets PA=1.29) and STS (Hedges g; Low PA=-0.72, Meets PA=-2.20) compared to Low PA. Six weeks of FRE+AE produced clinically meaningful neuromuscular and functional improvements in Veterans with CKD stages 3-4 irrespective of PA level, supporting FRE+AE as a feasible intervention in this population.