Impact of Pre-exercise Hypohydration on Aerobic Exercise Performance, Peak Oxygen Consumption and Oxygen Consumption at Lactate Threshold: A Systematic Review with Meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of controlled human trials
PubMed 31728846 · doi:10.1007/s40279-019-01223-5
What was done
A systematic review and meta-analysis of controlled human trials searched MEDLINE, SPORTDiscus, and CINAHL to assess the effect of pre-exercise hypohydration on aerobic exercise performance (AEP), peak oxygen consumption (VO2peak), and oxygen consumption at lactate threshold (VO2 at LT). Eligible studies enrolled adults (≥18 years), induced hypohydration ≥1 hour prior to exercise onset, achieved pre-exercise body mass loss ≥1% (and ≥0.5% greater than the well-hydrated control condition), and maintained control body mass within -1% to +0.5%.
What was found
Across 15 included manuscripts (186 subjects; mean body mass reduction 3.6 ± 1.0%, range 1.7–5.6%; mean test duration 22.3 ± 13.5 min, range 4.5–54.4 min): - Pre-exercise hypohydration impaired AEP by 2.4 ± 0.8% (95% CI 0.8–4.0%; 14 studies, 21 estimates). - Peak oxygen consumption decreased by 2.4 ± 0.8% (95% CI 0.7–4.0%; 6 studies, 10 estimates). - VO2 at lactate threshold decreased by 4.4 ± 1.4% (95% CI 1.7–7.1%; 6 studies, 9 estimates). - Meta-regression showed no significant relationship between body mass loss and percent change in AEP or VO2 at lactate threshold; however, VO2peak decreased by 2.6 ± 0.8% (95% CI 0.7–4.5%) for each 1% body mass loss exceeding a 2.8% loss threshold.
Why it matters
This review establishes that entering exercise hypohydrated independently impairs aerobic performance and submaximal/peak metabolic capacity during running and cycling under 1 hour, across temperatures from 19 to 40 °C.
Limits
The total sample size across 15 trials was modest (186 subjects), and mechanistic outcomes (VO2peak and VO2 at LT) included only 6 studies each. Exercise durations were relatively short (mean ~22 min, max 54.4 min), limiting generalizability to prolonged endurance events. The abstract does not report participant sex distributions, training status, or dehydration methods.
Cited by
- supports Even a slight degree of dehydration can impair cognitive and physical performance.