Resting blood pressure adaptations to isometric exercise training: Does muscle mass or systemic biomarkers help explain it?

Isometric exercise training (IET) reliably reduces resting blood pressure (BP) in normotensive and hypertensive populations. Despite little being known about the mechanisms that underlie these changes, they are likely multifaceted, given the complexity underlying regulation of blood pressure. This preliminary study examined several possible mechanisms underlying the resting BP adaptations to IET among 40 normotensive young adult males (20.3 ± 0.2 years; 85% White). Participants engaged in IET [bilateral biceps (n = 14) or quadriceps (n = 14)] three times per week or control, (no IET; n = 12) for six weeks and completed a pre- and post-intervention visit that involved venous blood draws and arterial blood pressure assessment. Resting systolic BP reduced similarly from baseline in both IET groups (-3.43 ± 1.3 mmHg). In comparison, the control group increased (2.39 ± 1.0 mmHg) over the six weeks (p < 0.05). Hence, muscle mass used in IET did not influence systolic BP adaptations. There was no significant change in diastolic BP and no group or time differences in systemic biomarker levels at six weeks. Neither systemic vascular endothelial growth factor-A (VEGF-A) at baseline nor the pre- to post-intervention change explained the resting systolic BP changes observed in the IET groups. However, baseline systemic inflammation and the pre- to post-intervention change predicted adaptations in resting systolic BP at the end of training, while controlling for pre-training BP. These findings suggest that reductions in resting systolic BP adaptations among normotensive young men may be associated with lower systemic inflammation before IET and an increase in systemic inflammation following six weeks of IET. The implications of these results are discussed as well as directions for further research.