Blood flow and oxygenation in peritendinous tissue and calf muscle during dynamic exercise in humans

1. Circulation around tendons may act as a shunt for muscle during exercise . The perfusion and oxygenation of Achilles' peritendinous tissue was measu red in parallel with that of calf muscle during exercise to determine (1) w hether Mood flow is restricted in peritendinous tissue during exercise, and (2) whether blood flow is coupled to oxidative metabolism. 2. Seven individuals performed dynamic plantar flexion from 1 to 9 W. Radia l artery and popliteal venous blood were sampled for O-2 peritendinous bloo d flow was determined by Xe-133-washout, calf blood flow by plethysmography , cardiac output by dye dilution, arterial pressure by an arterial catheter -transducer, and muscle and peritendinous O-2 saturation by spatially resol ved spectroscopy (SRS). 3. Calf blood flow rose 20-fold with exercise, reaching 44 +/- 7 ml(100 g)( -1) min(-1) (mean +/- S.E.M.) at 9 W, while Achilles' peritendinous flow in creased (7-fold) to 14 +/- 4 ml (100 g)(-1) min(-1) which was 18% of the ma ximal flow established during reactive hyperaemia. SRS-O-2 saturation fell both in muscle (from 66 +/- 2% at rest to 57 +/- 3%, P < 0.05) and in perit endinous regions (58 +/- 4 to 52 +/- 4%, P < 0.05) during exercise along wi th a rise in leg vascular conductance and microvascular haemoglobin volume, despite elevated systemic vascular resistance. 4. The parallel rise in calf muscle and peritendinous blood flow and fall i n O-2 saturation during exercise indicate that blood flow is coupled to oxi dative metabolism in both tissue regions. Increased leg vascular conductanc e accompanied by elevated microvascular haemoglobin volume reflect vasodila tation in both muscle and peritendinous regions. However, peak exercise per itendinous Mood flow reaches only similar to 20 % of its maximal blood flow capacity.