Swimming-related effects on cerebrovascular and cognitive function.

Both acute and regular exercise influence vascular and cognitive function. Upright aquatic exercise increases mean middle cerebral artery blood velocity (MCAv _mean ) and has been suggested as favorable for cerebrovascular adaptations. However, MCAv _mean has not been reported during swimming. Thus, we examined the cerebrovascular and cognitive effects of swimming. Ten land-based athletes (22 ± 5 years) and eight swimmers (19 ± 1 years) completed three cognitive tasks and four conditions that were used to independently and collectively delineate the swimming-related factors (i.e., posture, immersion, CO ₂ retention [end-tidal CO ₂ ; PETCO ₂ ], and motor involvement). Measurements of MCAv _mean and PETCO ₂ were taken throughout each condition. Prone posture increased MCAv _mean by 11% (P < 0.01 vs. upright land). Water immersion independently increased MCAv _mean when upright (12%; P < 0.01) but not prone (P = 0.76). The consequent rise in PETCO ₂ during head-out, breast-stroke swimming (50% heart rate range) independently increased MCAv _mean by 14% (P < 0.01), while the motor involvement of swimming per se did not significantly change MCAv _mean (P = 0.32). While accounting for sex, swimmers had ~17% lower MCAv _mean during all rest conditions (P ≤ 0.05). However, in a subset of participants, both groups had similar internal carotid artery diameters (P = 0.99) and velocities (P = 0.97). Water immersion per se did not alter cognition (P ≥ 0.15), but 20 min of moderate-intensity swimming improved visuomotor performance by 4% (P = 0.03), regardless of athlete group (P = 0.12). In conclusion, breast-stroke swimming increased MCAv _mean mostly due to postural and PETCO ₂ effects, with minimal contributions from water immersion or motor activity. Lastly, swimming improved cognitive functioning acutely, regardless of athlete group. Future research should explore the chronic effects of swimming on cerebrovascular function and cognition, particularly in aging.
(© 2019 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)