Local and central circulatory responses to sustained contractions and the effect of free or restricted arterial inflow on post-exercise hyperaemia.

1. The cardiovascular responses to sustained contractions at tensions from 5 to 30% maximal voluntary contraction (MVC) have been examined. At 5 and 10% MVC blood pressure, heart rate and forearm blood flow all reached a steady state during the contraction; post-exercise hyperaemia did not show peak flows higher than those found during exercise. At tensions of 20 and 30% MVC, none of the measurements showed a steady state during the contractions, but increased steadily throughout the contraction; post-exercise hyperaemia characteristically showed peak flows in excess of any flow measured during contractions. The results obtained at a tension of 15% MVC did not show a steady-state during the contraction but the following hyperaemia showed a similar pattern to that seen at the lower tensions.2. Digital compression of the brachial artery after sustained handgrip contractions for periods of 3 or 6 min after the contraction ended resulted in only a small reduction, on average by 5-15%, of the post-exercise hyperaemia.3. Consideration of the evidence leads to the view that in physiological circumstances the post-exercise hyperaemia following sustained contractions bears a close relationship to the metabolism of the active muscles.