Near infrared spectroscopy to evaluate the effect of a hybrid exercise programme on peripheral muscle metabolism in patients with intermittent claudication: an exploratory PROSECO-IC sub study.

Intermittent claudication (IC) is characterized by decreased blood flow and oxygen delivery to the lower-limb muscles, resulting in pain and impaired functional capacity. This study evaluated the effects of a 12-week hybrid walking intervention on muscle oxygenation and functional capacity in 38 patients with IC (Rutherford I-III). Functional capacity was evaluated by means of two different treadmill test protocols and a six-minute walk test (6MWT). Muscle oxygenation was assessed during the treadmill tests using near-infrared spectroscopy. After the intervention, maximal walking distance was significantly increased (p < 0.001) during the progressive maximal treadmill test (mean (SD): +155 (SD 177) metres) and 6MWT (+18 (SD 29) metres) metres, with concomitant improvements in muscle oxygenation measures. Deoxygenation was slower during the progressive maximal test (p < 0.001) and reoxygenation was faster during recovery (p = 0.045). During the more submaximal test, oxygenated haemoglobin was better preserved (p = 0.040). Slower deoxygenation was more pronounced in the high responders of the progressive maximal treadmill test (p = 0.002). The findings suggest that preserved oxygen availability and slower deoxygenation during exercise could partly explain the improvements in functional capacity.