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 contraction s . 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 su bjects [mean age 21 (SD 1) years] who exercised for 1 min at 33% of their m aximal voluntary contraction at ankle angles between 90 degrees and 100 deg rees. Spatially resolved near-infrared spectroscopy was used to measure med ial gastrocnemius, lateral soleus (synergist) and anterior tibialis (antago nist) muscle oxygen saturation (SO2, %). (Q) over dot(fa) was measured by u ltrasound Doppler. The SO2 changed significantly only in the medial gastroc nemius and its decrease (up to about 30%) was independent of the contractio n frequencies examined. The increase in (Q) over dot(fa), at the end of exe rcise, was highest at 80 cpm. When the exercise at 60 cpm was prolonged unt il exhaustion [mean 2.7(SD 1.1) min], medial gastrocnemius SO2 decreased, r eaching its minimal Value [mean 30 (SD 10)%] within the Ist min, and had pa rtially recovered before the end of the exercise with concomitant increases in total haemoglobin content and (Q) over dot(fa). These results suggest t hat the medial gastrocnemius is the muscle mostly involved in dynamic plant ar flexion exercise and its oxygen demand with increases in contraction fre quency and duration is associated with an up-stream increase in (Q) over do t(fa).