Reproducibility of Arterialized-Venous Blood Gas Samples at Moderate-, Heavy-, and Severe-Intensity Exercise
Bibliographic record
Abstract
We assessed the day-to-day variability of arterialized-venous blood gas, electrolyte, and metabolite responses during cycling exercise within the moderate-, heavy-, and severe-intensity domains. We hypothesized that arterialized-venous blood variables would be consistent between-days at each exercise intensity. Fourteen healthy participants (mean ± SD [range], 55 ± 13 [36-75] years, [Formula: see text]O 2max = 34.1 ± 11.1 [16.2-49.7] mL·kg -1 ·min -1 ; 7 females) completed a maximal incremental cycling exercise protocol (Visit 1) and two step-incremental protocols (Visits 2 and 3) over three days. The step-incremental protocol involved three stages of exercise consisting of two 10-min stages, within the moderate- (MOD; 80% gas exchange threshold (GET)), and heavy-intensity domains (HVY; 70% between the GET and respiratory compensation point (RCP)) and a third stage within the severe-intensity domain (SVR; above RCP) until task disengagement. During MOD and HVY, 1.5 mL blood samples were withdrawn into heparinized syringes through a catheter placed in a heated hand vein at 5.0 and 7.5 minutes following stage onset and during the final minute of exercise in SVR. Blood samples were immediately analysed by a blood gas analyzer (ABL90Flex, Radiometer, Denmark). Two-way repeated measures ANOVA (intensity x day) and Pearson correlation coefficient (R) were used to assess between-day reproducibility at each intensity. Average power output for MOD, HVY, and SVR were 92±39 W, 130±50 W, and 169±74 W, respectively, eliciting steady-state [Formula: see text]O 2 of 1.54±0.57 L · min -1 , 1.99±0.73 L · min -1 , and peak [Formula: see text]O 2 of 2.46±1.00 L · min -1 . A significant main effect of intensity was found for all variables (p<0.05) but not for blood glucose ([Glu]; p=0.08). There was no main effect of day or intensity x day interaction for all variables. Combining all intensities, mean between-day changes were: pH: 0.01±0.02 (p=0.48, R=0.85); partial pressure of CO 2 : 0.4±2.3 mmHg (p=0.79, R=0.86);blood lactate concentration: 0.3±1.3 mmol . L -1 (p=0.25, R=0.92); [Glu]: 0.2±1.0 mmol . L -1 (p=0.64, R=0.17); bicarbonate concentration: -0.2±1.0 mmol . L -1 (p=0.32, R=0.90); potassium: 0.02±0.31 mmol . L -1 (p=0.57, R=0.83); sodium [Na + ]): 0.02±1.70 mmol . L -1 (p=0.91, R=0.78); calcium: 0.00±0.03 mmol . L -1 (p=0.23, R=0.57); and chloride: -0.66±2.62 mmol . L -1 (p=0.50, R=0.57). Arterialized-venous blood gas, electrolyte, and metabolite variables exhibited excellent test-retest reproducibility between-days. This was consistent irrespective of exercise intensity. Daniel A. Keir was supported by a NSERC Discovery Grant and the Canadian Foundation for Innovation. Robin Faricier was supported by an Ontario Graduate Scholarship. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
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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 | 0.001 | 0.003 |
| 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) | 0.000 | 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 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".