Abstract
Effects of exercise‐heat stress with and without water replacement on brain structure and visuomotor performance were examined. Thirteen healthy adults (23.6 ± 4.2 years) completed counterbalanced 150 min trials of exercise‐heat stress (45°C, 15% RH) with water replacement (EHS) or without (~3% body mass loss; EHS‐DEH) compared to seated rest (CON). Anatomical scans and fMRI Blood‐Oxygen‐Level‐Dependent responses during a visuomotor pacing task were evaluated. Accuracy decreased (P < 0.05) despite water replacement during EHS (−8.2 ± 6.8% vs. CON) but further degraded with EHS‐DEH (−8.3 ± 6.4% vs. EHS and −16.5 ± 10.2% vs. CON). Relative to CON, EHS elicited opposing volumetric changes (P < 0.05) in brain ventricles (−5.3 ± 1.7%) and periventricular structures (cerebellum: 1.5 ± 0.8%) compared to EHS‐DEH (ventricles: 6.8 ± 3.4, cerebellum: −0.7 ± 0.7; thalamus: −2.7 ± 1.3%). Changes in plasma osmolality (EHS: −3.0 ± 2.1; EHS‐DEH: 9.3 ± 2.1 mOsm/kg) were related (P < 0.05) to thalamus (r = −0.45) and cerebellum volume (r = −0.61) which, in turn, were related (P < 0.05) to lateral (r = −0.41) and fourth ventricle volume (r = −0.67) changes, respectively; but, there were no associations (P > 0.50) between structural changes and visuomotor accuracy. EHS‐DEH increased neural activation (P < 0.05) within motor and visual areas versus EHS and CON. Brain structural changes are related to bidirectional plasma osmolality perturbations resulting from exercise‐heat stress (with and without water replacement), but do not explain visuomotor impairments. Negative impacts of exercise‐heat stress on visuomotor tasks are further exacerbated by dehydration.
Highlights
Prevention of significant dehydration by replacing fluids during exercise in the heat attenuates adverse physiological effects such as reduced aerobic performance (Kenefick 2018)
Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society
Baseline hydration status was similar across all trials with no differences in urine specific gravity (USG) (CON: 1.017 Æ 0.003, exercise-heat stress with fluid replacement (EHS): 1.020 Æ 0.003, exercise-heat stress with dehydration (EHS-DEH): 1.016 Æ 0.003; P = 0.86) or plasma osmolality (POsm) (CON: 283.8 Æ 2.7, EHS: 283.6 Æ 2.6, EHS-DEH: 284.5 Æ 2.2 mOsm/kg; P = 0.36)
Summary
Prevention of significant dehydration by replacing fluids during exercise in the heat attenuates adverse physiological effects such as reduced aerobic performance (Kenefick 2018). Since dehydration is a common stressor occurring with prolonged heat exposure in various occupational and military settings, whether fluid replacement mitigates cognitive-motor deficits is an important question. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have