An acute concurrent exercise bout better preserves cerebrovascular reactivity to hypocapnia than either resistance or aerobic exercise.

PURPOSE: To investigate the acute effects of concurrent exercise (CE), resistance exercise (RE), and moderate-intensity continuous exercise (MICE) on cerebrovascular reactivity (CVR) to hypocapnia. METHODS: Twenty-four healthy young adults (12 males) completed four 30-min, time-matched experimental visits in a randomised order: seated rest (CON), RE (4×10 repetitions of four exercises at 70% one-repetition maximum, 1-RM), MICE (cycling at 90% gas exchange threshold, GET), and CE (2×10 repetitions at 70% 1-RM followed by 15-min cycling at 90% GET). CVR was assessed before and 20 min after each condition using 1-min of voluntary hyperventilation (25 breaths·min⁻1). Mean middle cerebral artery blood velocity (MCAv) was measured via transcranial Doppler ultrasound, and end-tidal CO₂ (PETCO₂) was measured breath-by-breath. CVR was calculated as the change in MCAv per 1 mmHg change in PETCO₂. RESULTS: Resting PETCO₂ was reduced following all exercise conditions (P<0.05), but CVR to hypocapnia did not differ from pre- to post-condition in any trial (CON: 1.70±0.44 vs 1.72±0.48 cm·s⁻1·mmHg⁻1, P=0.52; RE: 1.57±0.38 vs 1.53±0.35 cm·s⁻1·mmHg⁻1, P=0.36; MICE: 1.61±0.34 vs 1.54±0.47 cm·s⁻1·mmHg⁻1, P=0.31; CE: 1.70±0.35 vs 1.73±0.44 cm·s⁻1·mmHg⁻1, P=0.77). Post-exercise CVR, however, was lower following RE compared with CON (P=0.02) and CE (P=0.01), and lower following MICE compared with CE (P=0.04), with no baseline differences among conditions. CONCLUSION: CVR to hypocapnia was preserved 20 min following CE, RE and MICE in healthy young adults. However, post-exercise CVR was lower following RE than CON and CE, and lower following MICE than CE, despite similar baseline values, suggesting modality-specific cerebrovascular responses during recovery.