Key Points
- This research aimed to examine how lactate and protons are released and transported in muscles during intense exercise under different oxygen conditions.
- Subjects performed two-legged knee-extensor exercise in normoxia and hypoxia over various phases for 29-35 minutes.
- Arterial blood samples were collected to measure lactate, H+, and pH levels before and during exercise phases.
- Leg blood flow was monitored to assess muscle metabolism.
- Arterial lactate concentration increased to 5.9 mmol/l (N) and 8.2 mmol/l (H) after 5.5 min of exercise (P < 0.05).
- Net proton release was significant throughout exercise phases (P < 0.05) despite blood pH variations.
- Muscle transport of protons during submaximal exercise occurred independently of lactate levels.
Structured PICO
PPopulationHuman subjects performing two-legged submaximal knee-extensor exercise
IInterventionBreathing 14% O2 in N2 (hypoxia, H) during exercise protocol
CComparatorInspiring air (normoxia, N) during the same exercise protocol
OOutcomeTransport of lactate, H+ and fluid across muscle sarcolemma (assessed by leg blood flow and femoral arterial/venous blood sampling)surrogate
H+ exchange in muscle during submaximal exercise can largely occur through mechanisms other than coupling to lactate, and muscle transport of H+ is insensitive to small changes in blood pH.