Haemodynamic advantage of the Valsalva manoeuvre during heavy resistance training

A nuclear probe was used to assess beat-to-beat changes in relative cardiac output in eight elite athletes during isometric exercise. Three subjects underwent simultaneous intra-arterial blood pressure recording. Stroke volume fell by 68 +/- 4% during Valsalva's manoeuvre alone, but by 42 +/- 9% with simultaneous isometric handgrip. Blood pressure changes during isometric handgrip were significantly modified by simultaneous Valsalva's manoeuvre. In particular no late strain phase fall or post-strain overshoot in blood pressure was seen, hence there was no baroreceptor-mediated fall in heart rate. Maximum Valsalva's manoeuvres in athletes invoked extreme falls in cardiac output and blood pressure which were attenuated by simultaneous isometric handgrip. The mechanism of this may be twofold: increased venous tone maintains stroke volume; and/or increased arteriolar tone maintains blood pressure.