Peak oxygen consumption is positively associated with estimates of oxygen extraction and microvascular blood volume in veterans with chronic kidney disease.

Peak oxygen consumption (V̇o2peak) is reduced in patients with chronic kidney disease (CKD). Although cardiovascular and skeletal muscle factors are implicated in the declines of V̇o2peak, few studies have evaluated muscle oxygenation responses during exercise. We hypothesized that lower V̇o2peak in CKD would be associated with attenuated responses in muscle oxygenation compared with those without CKD. Forty-six male Veterans [CKD stages 3 and 4, n = 23; referent controls (REF), n = 23] completed the study. Cardiopulmonary exercise testing was performed on a treadmill using the modified Bruce protocol. Peak change in dominant medial gastrocnemius deoxygenated hemoglobin/myoglobin {Δ[deoxy(Hb-Mb)]peak}, total hemoglobin/myoglobin {Δ[total(Hb-Mb)]peak}, tissue saturation index (ΔTSI), and ΔTSI reoxygenation half-time recovery (ΔTSIreoxy1/2time) were assessed via near-infrared spectroscopy (NIRS). V̇o2peak, exercise time, HRpeak, V̇o2 at gas-exchange threshold (GET), and exercise time after GET were lower in the CKD group versus the REF group (P = 0.002, P < 0.001, P = 0.020, P = 0.044, and P = 0.005, respectively). For NIRS outcomes, Δ[total(Hb-Mb)]peak was lower, and ΔTSIreoxy1/2time prolonged, in the CKD group compared with the REF group (P = 0.032 and P = 0.031, respectively). V̇o2peak was positively associated with HRpeak (CKD, r = 0.57, P = 0.005; REF, r = 0.63, P = 0.001) and Δ[total(Hb-Mb)]peak (CKD, r = 0.63, P = 0.001; REF, r = 0.52, P = 0.012) in both groups. Conversely, V̇o2peak was positively associated with Δ[deoxy(Hb-Mb)]peak in the CKD group only (r = 0.64, P < 0.001). These findings suggest that skeletal muscle impairments, in addition to cardiovascular impairments, contribute to reduced V̇o2peak in patients with CKD.NEW & NOTEWORTHY Peak oxygen consumption is associated with peak heart rate, oxygen extraction, and microvascular blood volume in patients with chronic kidney disease (CKD), highlighting the importance of cardiovascular and skeletal muscle health in this patient population. Future studies are necessary to determine which exercise approaches are most efficacious at enhancing cardiorespiratory fitness and whether, and to what extent, improvements in cardiorespiratory fitness result from changes in cardiovascular factors, skeletal muscle factors, or a combination of both.