Figure 5. Changes in intercostal and quadriceps oxygenation during exercise and isocapnic, resting hyperpnoea.

Changes in oxygen saturation and deoxygenated haemoglobin concentration for the intercostal muscles (A and B) and the quadriceps muscles (C and D) at different levels of minute ventilation during exercise (open triangles) and isocapnic, resting hyperpnoea (filled triangles). Values are means ±s.e.m. for 10 subjects. Asterisks denote significant differences between the exercise and hyperpnoea tests; double crosses denote significant differences compared to baseline, P < 0.05.