Abnormally elevated intramuscular pressure impairs muscle blood flow at rest after exercise

We used photoplethysmography (PPG) to measure the relative changes in the anterior tibial muscle blood flow (MBF) in response to exercise when intramuscular pressure (IMP) was elevated (the test leg) or when IMP was normal (the control leg). The elevated IMP was induced by applying venous obstruction of 40 mmHg or 65 mmHg (thigh tourniquet) of a casted leg in eight healthy subjects. Subjects performed dorsiflexion of both feet in sitting position with or without venous obstruction. IMP at rest after exercise increased to 39.4+/-7.9 mmHg or to 58.3+/-8.4 mmHg, respectively. MBF at rest before exercise was 100%. At rest after exercise, it increased to 184+/-52.6% in the test leg when IMP was 39.4 mmHg, and to 279+/-108.3% in the control leg. MBF at rest after exercise was 156+/-58.2% in the test leg when IMP was 58.3 mmHg and 303+/-95.3% in the control leg. The abnormally elevated IMP induced by venous obstruction of a casted leg reduced MBF at rest after exercise. PPG seems to be a suitable method to measure changes in MBF in response to exercise and in experimental conditions with abnormally elevated IMP.