Calf and shin muscle oxygenation patterns and femoral artery blood flow during dynamic plantar flexion exercise in humans

The effects of dynamic plantar flexion exercise [40, 40, and 80 contractions . min(-1) (cpm)] on calf and shin muscle oxygenation patterns and common femoral artery blood flow ((Q) over dot(fa)) were examined in six female subjects [mean age 21 (SD 1) years] who exercised for 1 min at 33% of their maximal voluntary contraction at ankle angles between 90 degrees and 100 degrees. Spatially resolved near-infrared spectroscopy was used to measure medial gastrocnemius, lateral soleus (synergist) and anterior tibialis (antagonist) muscle oxygen saturation (SO2, %). (Q) over dot(fa) was measured by ultrasound Doppler. The SO2 changed significantly only in the medial gastrocnemius and its decrease (up to about 30%) was independent of the contraction frequencies examined. The increase in (Q) over dot(fa), at the end of exercise, was highest at 80 cpm. When the exercise at 60 cpm was prolonged until exhaustion [mean 2.7(SD 1.1) min], medial gastrocnemius SO2 decreased, reaching its minimal Value [mean 30 (SD 10)%] within the Ist min, and had partially recovered before the end of the exercise with concomitant increases in total haemoglobin content and (Q) over dot(fa). These results suggest that the medial gastrocnemius is the muscle mostly involved in dynamic plantar flexion exercise and its oxygen demand with increases in contraction frequency and duration is associated with an up-stream increase in (Q) over dot(fa).