The Magnitude Of Exercise-induced Hypervolemia Following High-intensity Interval Exercise Depends On Session Duration
Bibliographic record
Abstract
The mechanisms of blood volume expansion during endurance training are poorly understood, but the exercise-induced increase in plasma volume ~ 24 hours post-exercise may act as an erythropoietic signal. PURPOSE: To determine the impact of high-intensity interval exercise duration on plasma volume responses. METHODS: On separate days, 16 healthy, recreationally active participants (n = 8 males; n = 8 females) performed four (4x4) or eight intervals (8x4) consisting of 4 min at 105% critical power interspersed with 3 min rest. We collected venous blood samples before, immediately after, and 24 hours after each HIIT session. Changes in plasma volume from baseline were calculated using hemoglobin concentration and hematocrit. Blood levels of renin, aldosterone, and NTpro-ANP (corrected for plasma volume changes) were measured using ELISA kits to assess plasma volume regulation. Data were analyzed using two-way, repeated measures ANOVAs and followed with Tukey’s multiple comparison tests. Results were considered statistically significant at p < 0.05. RESULTS: Plasma volume (Figure 1A) decreased from baseline immediately after both protocols (4x4: -4.4 ± 3.5%, p < 0.05; 8x4: -4.4 ± 3.6%, p < 0.05) but was only significantly elevated above baseline 24 hours after the 8x4 protocol (4x4: 1.0 ± 7.1%, p > 0.05; 8x4: 5.6 ± 4.6%, p < 0.05). Renin (1B) was higher than baseline immediately post-exercise after the 8x4 protocol. NTpro-ANP (1C) and aldosterone (1D) were both higher than baseline immediately post-exercise after both protocols, but the increases were larger following the 8x4 protocol. CONCLUSIONS: Doubling HIIT volume caused higher post-exercise concentrations of key hormones and an increase in plasma volume that was not observed following the 4x4 condition. There appears to be a minimum duration of interval exercise necessary to induce hypervolemia following a single session.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".