Acute cardiac autonomic and haemodynamic responses to leg and arm isometric exercise

Objectives <br /><br />Acute cardiovascular responses following a single session of isometric exercise (IE) have been shown to predict chronic adaptations in blood pressure (BP) regulation. It was hypothesised that exercises which recruit more muscle mass<br />induce greater reductions in BP compared to exercises using smaller muscle mass. To test this hypothesis, the current study aimed to compare the acute haemodynamic and autonomic responses to a single session of isometric wall squat (IWS) and isometric handgrip (IHG) training.<br /><br />Methods <br /><br />Twenty-six sedentary participants performed a single IWS and IHG session in a randomised cross-over design, with training composed of 4×2-min contractions, with 2-min rest, at 95 HRpeak and 30% MVC respectively. Haemodynamic<br />and cardiac autonomic variables were recorded pre, during, immediately post, and 1-h post-exercise, with the change from baseline for each variable used for comparative analysis.<br /><br />Results<br /><br />During IWS exercise, there was a signifcantly greater increase in systolic BP (P<0.001), diastolic BP (P<0.001), mean BP (P<0.001), heart rate (P<0.001), and cardiac output (P<0.001), and a contrasting decrease in barorefex efectiveness index (BEI) and cardiac baroreceptor sensitivity (cBRS). In the 10-min recovery period following IWS exercise, there was a signifcantly greater reduction in systolic BP (P=0.005), diastolic BP (P=0.006), mean BP (P=0.003), total<br />peripheral resistance (TPR) (P<0.001), BEI (P=0.003), and power spectral density (PSD-RRI) (P<0.001). There were no diferences in any variables between conditions 1-h post exercise.<br /><br />Conclusions <br /><br />Isometric wall squat exercise involving larger muscle mass is associated with a signifcantly greater post-exercise hypotensive response during a 10-min recovery window compared to smaller muscle mass IHG exercise. The signifcantly greater reduction in TPR may be an important mechanism for the diferences in BP response.