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

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 CO 2 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 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.