No differences in the erythropoietin response to acute high-intensity exercise when duration is doubled, despite augmented post-exercise plasma volume expansion
Bibliographic record
Abstract
The increase in plasma volume ∼24 h post-exercise may act as an erythropoietic signal; however, the responsiveness of this mechanism to different exercise prescription variables is poorly understood. The purpose of this study was to determine the impact of high-intensity interval exercise duration on erythropoietic signalling and plasma volume expansion. On separate days, 16 healthy, recreationally active participants ( n = 8 males; n = 8 females) performed four (4 × 4 HIIT) or eight intervals (8 × 4 HIIT) consisting of 4 min at 105% critical power with 3 min recovery. Venous blood samples were collected before, immediately after, and 24 h after each HIIT session to measure hemoglobin concentration and hematocrit to calculate plasma volume changes. Erythropoietic and plasma volume regulating hormone concentrations were measured using ELISA kits. Circulating erythropoietin mass was elevated 24 h after HIIT (4 × 4: Pre vs. 4 h post: 22.2 ± 13.0 vs. 24.2 ± 13.6 IU; 8 × 4: 23.6 ± 14.6 vs. 24.9 ± 14.4 IU; p < 0.05) with no difference between protocols ( p > 0.05). Plasma volume decreased immediately after both protocols (4 × 4: −4.4 ± 3.5%, p < 0.05; 8 × 4: −4.4 ± 3.6%, p < 0.05) but was only significantly elevated above baseline 24 h after the 8 × 4 protocol (4 × 4: +1.1 ± 7.1%, p > 0.05; 8 × 4: +5.6 ± 4.6%, p < 0.05). Aldosterone concentration was elevated post-exercise after both protocols (4 × 4: Pre vs. 0 h post: 295 ± 151 vs. 570 ± 271 pg/mL; 8 × 4: 335 ± 235 vs. 854 ± 566 pg/mL), but the 8 × 4 protocol caused a larger increase ( p < 0.05). Post-exercise hypervolemia depends on exercise duration, but hypervolemia is not required for increases in circulating erythropoietin, challenging the importance of this mechanism for endurance training-induced increases in hemoglobin mass and oxygen-carrying capacity.
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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 | 0.000 |
| 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 | 0.000 |
| 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".