The Effect of Fluid Intake Following Dehydration on Subsequent Athletic and Cognitive Performance: a Systematic Review and Meta-analysis

Abstract

Background: The deleterious effects of dehydration on athletic and cognitive performance have been well documented. As such, dehydrated individuals are advised to consume fluid in volumes equivalent to 1.25 to 1.5 L kg^-1 body mass (BM) lost to restore body water content. However, individuals undertaking subsequent activity may have limited time to consume fluid. Within this context, the impact of fluid intake practices is unclear. This systematic review investigated the effect of fluid consumption following a period of dehydration on subsequent athletic and cognitive performance.

Methods: PubMed (MEDLINE), Web of Science (via Thomas Reuters) and Scopus databases were searched for articles reporting on athletic (categorized as: continuous, intermittent, resistance, sport-specific and balance exercise) or cognitive performance following dehydration of participants under control (no fluid) and intervention (fluid intake) conditions. Meta-analytic procedures determined intervention efficacy for continuous exercise performance.

Results: Sixty-four trials (n = 643 participants) derived from 42 publications were reviewed. Dehydration decreased BM by 1.3-4.2%, and fluid intake was equivalent to 0.4-1.55 L kg^-1 BM lost. Fluid intake significantly improved continuous exercise performance (22 trials), Hedges' g = 0.46, 95% CI 0.32, 0.61. Improvement was greatest when exercise was performed in hotter environments and over longer durations. The volume or timing of fluid consumption did not influence the magnitude of this effect. Evidence indicating a benefit of fluid intake on intermittent (10 trials), resistance (9 trials), sport-specific (6 trials) and balance (2 trials) exercise and on cognitive performance (15 trials) was less apparent and requires further elucidation.

Conclusions: Fluid consumption following dehydration may improve continuous exercise performance under heat stress conditions, even when the body water deficit is modest and fluid intake is inadequate for complete rehydration.

Keywords: Athletic; Cognitive; Dehydration; Fluid intake; Mood; Performance.

Fig. 1

PRISMA Flow Chart (study selection methodology). Where a study contained >1 intervention-arm that was eligible for inclusion (i.e. paired against a suitable control condition), these were treated as separate ‘studies’ termed ‘trials’

Fig. 2

A schematic representation of the experimental protocol employed in studies eligible for inclusion in the present review

Fig. 3

Forest plot displaying the effect of fluid intake on continuous exercise performance. Size of the squares is proportional to the weight of the study

Fig. 4

Correlation between change in ambient environmental temperature and change in continuous exercise performance (Hedges’ g). Circle diameter corresponds to the weight of each study. Hedges g = −0.105 + 0.024 × temperature (°C)

Fig. 5

Correlation between change in fluid intake (L kg BM lost⁻¹) and change in continuous exercise performance (Hedges’ g) controlling for ambient environmental temperature, exercise duration, level of dehydration and the ecological validity of the exercise protocol. Circle diameter corresponds to the weight of each study. Hedges g = −0.557 + 0.002 × fluid volume (L kg BM lost⁻¹) + 0.025 × temperature (°C) + 0.011 × exercise duration (min) + 0.218, if ecologically valid + 0.0126 × level of dehydration (% BM lost)