Gollie JM; Research and Development Washington DC VA Columbria USA
Kokkinos PF; Patel SS; Libin AV; Holley AB; Shara NM; Hazel CG;
Kim DJ; Blackman MR

American Journal of Physiology – Renal Physiology. 330(5):F631-F640, 2026 May 01

Headings by Dr Older

Background
Peak oxygen consumption (Vo2peak) is reduced in patients with chronic
kidney disease (CKD). Although cardiovascular and skeletal muscle factors
are implicated in the declines of Vo2peak, few studies have evaluated
muscle oxygenation responses during exercise. We hypothesized that lower
Vo2peak in CKD would be associated with attenuated responses in muscle
oxygenation compared with those without CKD.
Methods
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 {DELTA[deoxy(Hb-Mb)]peak}, total
hemoglobin/myoglobin {DELTA[total(Hb-Mb)]peak}, tissue saturation index
(DELTATSI), and DELTATSI reoxygenation half-time recovery
(DELTATSIreoxy1/2time) were assessed via near-infrared spectroscopy
(NIRS).
Results
Vo2peak, exercise time, HRpeak, Vo2 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, DELTA[total(Hb-Mb)]peak was lower, and
DELTATSIreoxy1/2time prolonged, in the CKD group compared with the REF
group (P = 0.032 and P = 0.031, respectively). Vo2peak was positively
associated with HRpeak (CKD, r = 0.57, P = 0.005; REF, r = 0.63, P =
0.001) and DELTA[total(Hb-Mb)]peak (CKD, r = 0.63, P = 0.001; REF, r =
0.52, P = 0.012) in both groups. Conversely, Vo2peak was positively
associated with DELTA[deoxy(Hb-Mb)]peak in the CKD group only (r = 0.64, P
< 0.001).
Conclusions
These findings suggest that skeletal muscle impairments, in
addition to cardiovascular impairments, contribute to reduced Vo2peak 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.