Meta-Analysis Of The Effects Of Pre-Exercise Hypohydration On Endurance Performance, Lactate Threshold And Vo2max
Bibliographic record
Abstract
Exercise-induced dehydration (EID) ≥ 2% bodyweight (BW) impairs endurance performance (EP). It is unclear how pre-exercise hypohydration (PEH), which may impose physiological challenges differing from those of EID, affects EP, VO2 at lactate threshold (VO2LT) and maximal oxygen consumption (VO2max). PURPOSE: To determine the magnitude of the effects of PEH on EP, VO2LT and VO2max using a meta-analytic approach. METHODS: Studies were located via database searches and cross-referencing. Inclusion criteria: BW loss incurred ≥ 1h prior to the exercise tests; hydration level in the control group < 0.5% ≥ -1% BW; hypohydration level in the experimental group > 1% BW and > 0.5% than control. Exclusion criteria: diuretics- and caloric restriction-induced BW loss. STATISTICS: Random-effect model for mean weighted summary effects, random-effect (method-of-moments) meta-regression for relationships between variables and random-effect analog to the ANOVA for subgroup analyses. Mean changes in EP times during incremental or fixed-power output tests to exhaustion were converted to mean changes in power output. RESULTS: Twenty-nine research articles were retrieved, among which 10, 7 and 7 met the inclusion criteria for EP, VO2LT and VO2max, respectively, providing 14, 10 and 11 effect estimates. Mean BW decreases in all experimental groups were 3.9 ± 0.9% (SD) (range 2.6 to 5.6%). EP and VO2LT: Mean exercise test times among studies was 21 ± 15 min. Mean power output fell by 3.2% (95% CI: 2.4 to 4.0%) and VO2LT by 5.63% (95% CI: 2.8 to 8.4%) in hypohydrated group relative to control. Percent change in power output and VO2LT did not differ between studies with BW losses ≤ 4% or > 4%. Meta-regression analyses did not establish significant relationship patterns between BW losses and percent changes in power output or VO2LTs. VO2max: With PEH VO2max decreased by 2.4% (95% CI: 1.1 to 3.8%) compared with control group. Percent change in VO2max in studies with BW losses ≤ 4% was significantly lower than in those with BW losses > 4%. VO2max was found to decrease by 2.9% for each percent loss in BW above a threshold loss of 3.1% (P = 0.027). CONCLUSIONS: Results indicate that PEH ≥ 3% BW impairs EP, VO2LT and VO2max in a practically important manner. Studies are required to establish how PEH in the 1-5% BW range affects EP during prolonged exercise.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".