Predicting Blood Flow Responses to Rhythmic Handgrip Exercise From One Second Isometric Contractions

The aim of this work was to predict blood flow responses to rhythmic handgrip exercise from one second isometric contractions. Seven healthy men were studied. Each subject performed a single 1 second handgrip contraction at 10%, 20% and 40% of the maximum handgrip strength. We then repeatedly summed hyperaemic responses from single contractions to predict hyperaemic response to a prolonged bout of rhythmic exercise. There was similarity between steady state brachial blood flow velocity (BBV) extrapolated from single handgrip contractions and during 2 minutes of rhythmic exercise for 20% (10.0±3.8cm/sec vs 10.2±2.6 cm/sec, r=0.93, p=0.003) and 40% of maximum contractions (14.2±5.5 cm/sec vs 15.6±3.4 cm/sec, r=0.88, p=0.009), but not for 10% (7.5±4.1 cm/sec vs 5.7±3.3 cm/sec, r=0.94, p=0.018). BBV progressively rose substantially higher during rhythmic contractions than peak BBV observed during single contractions at matched intensity. Respective peak BBV during single contractions and steady state BBV rhythmic contractions were 4.4±2.1 and 5.7±3.3 cm.s-1 at 10% forearm strength (p = 0.14), 5.6±2.4 and 10.2±2.8 cm.s-1 at 20% (p = 0.002), and 7.0±2.5 and 15.6±3.6 cm.s-1 at 40% (p = 0.003). There is similarity between the summated blood flow velocity calculated from a single 1 second muscle contraction and the steady state blood flow velocity response of rhythmic exercise.