RESUMO
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 (PCAvmean) and middle cerebral arteries (MCAvmean), 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 × condition) were observed for MCAvmean, PCAvmean, vertebral artery blood flow and MAP (all ≤ 0.010). Phase I MCAvmean 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 MCAvmean than PCAvmean 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 MCAvmean (78 ± 8 vs. 79 ± 9 cm s-1, P = 0.579) or PCAvmean (45 ± 11 vs .46 ± 11 cm s-1, P = 0.617). Phase IIb MCAvmean and PCAvmean was lowest in VM (66 ± 6 and 39 ± 8 cm s-1, respectively, all P < 0.001), whereas in Phase IV, MCAvmean, PCAvmean 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.
