Dehydration: physiology, assessment, and performance effects.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing physiology and performance literature without systematic search methodology.
PubMed 24692140 · doi:10.1002/cphy.c130017
What was done
This narrative review synthesized literature on dehydration assessment and its physiological effects on physical and cognitive performance. The authors evaluated the distinction between intracellular dehydration (hypo-osmotic water loss) and extracellular dehydration (iso-osmotic water loss), the role of diagnostic and biological variation in assessment baselines, and the threshold required to elicit measurable physiologic and performance changes across endurance, strength, power, and cognitive tasks.
What was found
The literature analysis identified a threshold of at least 2% dehydration for impaired endurance exercise performance mediated by volume loss. For strength and power performance, reported impairments were marginal with no clear threshold or plausible underlying mechanism. Cognitive performance impairments were characterized as small and primarily attributable to distraction or discomfort rather than direct physiological deficits. The abstract reports no quantitative effect sizes, pooled metrics, or participant numbers.
Why it matters
It distinguishes between intracellular and extracellular water loss mechanisms and identifies a 2% body mass deficit threshold specifically for endurance impairment while questioning strong physiological links to strength or cognitive declines.
Limits
As a narrative review, the synthesis lacks systematic search criteria, explicit study inclusion/exclusion standards, quality appraisal, and meta-analytic pooling. Numerical effect sizes and primary study counts are not provided in the abstract.
Cited by
- contradicts Even a slight degree of dehydration diminishes human cognitive and physical performance.