Cerebrovascular haemodynamics during isometric resistance exercise with and without the Valsalva manoeuvre.

Abstract

To examine the interactive effects of VM and isometric resistance exercise on cerebral haemodynamics. Eleven healthy participants (mean ± SD 28 ± 9years; 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 40mmHg (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. 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 ± 12cm 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 ± 21mmHg, P = 0.004), but did not reduce MCAvmean (78 ± 8 vs. 79 ± 9cm s-1, P = 0.579) or PCAvmean (45 ± 11 vs .46 ± 11cm s-1, P = 0.617). Phase IIb MCAvmean and PCAvmean was lowest in VM (66 ± 6 and 39 ± 8cm 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). RE and RE + VM produce similar cerebrovascular responses despite different MAP profiles. However, the VM produced the greatest cerebrovascular challenge afterward.