Figure 5. Effects of ribcage or diaphragm breathing patterns on femoral arterial inflow, MAP and femoral venous outflow signal averaged over the course of a breath during moderate calf contraction conditions (minimum of 120 breaths per subject per condition).

Similar to both resting and mild calf contraction conditions, the respiratory modulation of femoral arterial inflow and mean arterial pressure is negligible, though arterial inflow is now impeded due to the local compression of the arteries during the calf contraction (P < 0.05, nadir femoral arterial blood flow during the calf contraction phase versus calf relaxation phase, also see Fig. 6). Similar to mild calf contraction conditions, significant within-breath modulation of femoral venous blood flow persists during moderate calf contraction, as mean inspiratory and mean expiratory femoral venous blood flows are significantly different during the two breathing conditions. Grey circles, ribcage breathing; black circles, diaphragm breathing; †P < 0.01 and *P < 0.05 for comparisons of ribcage versus diaphragm for mean inspiratory or expiratory values.