GSTM1 and ischemia: Some studies have performed blood flow occlusions of the investigated limb either at rest or a few minutes after an exercise protocol to “physiologically calibrate” the NIRS device [7,9,48–51], with the overall amplitude of the deoxy[Hb+Mb] signal during the transient ischemia supposedly representing the range of O2 extraction from rest to complete desaturation [52].