Abstract
Purpose To examine the interactive effects of VM and isometric resistance exercise on cerebral haemodynamics. Methods Eleven healthy participants (mean +/- SD 28 +/- 9 years; 2 females) completed 20-s bilateral isometric leg extension at 50% of maximal voluntary contraction with continued ventilation (RE), a 20-s VM at mouth pressure of 40 mmHg (VM), and a combination (RE + VM), in randomised order. Mean beat-to-beat blood velocity in the posterior (PCAv(mean)) and middle cerebral arteries (MCAv(mean)), vertebral artery blood flow, end-tidal partial pressure of CO2 and mean arterial pressure (MAP) were measured. RE data were time aligned to RE + VM and analysed according to standard VM phases. Results Interaction effects (VM phase x condition) were observed for MCAv(mean), PCAv(mean), vertebral artery blood flow and MAP (all <= 0.010). Phase I MCAv(mean) was greatest for RE [88 +/- 19, vs. 71 +/- 11 and 78 +/- 12 cm s(-1) for VM (P = 0.008) and RE + VM (P = 0.021), respectively]. Greater increases in MCAv(mean) than PCAv(mean) occurred in phase I of RE only (24 +/- 15% vs. 16 +/- 16%, post hoc P = 0.044). In phase IIb, MAP was lower in RE than RE + VM (115 +/- 15 vs. 138 +/- 21 mmHg, P = 0.004), but did not reduce MCAv(mean) (78 +/- 8 vs. 79 +/- 9 cm s(-1), P = 0.579) or PCAv(mean) (45 +/- 11 vs .46 +/- 11 cm s(-1), P = 0.617). Phase IIb MCAv(mean) and PCAv(mean) was lowest in VM (66 +/- 6 and 39 +/- 8 cm s(-1), respectively, all P < 0.001), whereas in Phase IV, MCAv(mean), PCAv(mean) and MAP were greater in VM than in RE and RE + VM (all P < 0.020). Conclusion RE and RE + VM produce similar cerebrovascular responses despite different MAP profiles. However, the VM produced the greatest cerebrovascular challenge afterward.