A Direct Measure Of Leg Blood Flow During Running: A Feasibility Case Study
Bibliographic record
Abstract
Cardiac output and leg blood flow can be measured simultaneously with high accuracy using transpulmonary thermodilution and femoral vein thermodilution with a single bolus injection. These measurements have been performed during single leg kicking, cycling, and Nordic skiing, offering insights into competing blood flow demands during exercise. Running is the natural exercise modality of humans, however, to date there has been no direct measure of leg blood flow during running. PURPOSE: To determine the feasibility of the thermodilution technique to measure leg blood flow and conductance during high intensity running relative to cycling, in an exploratory case study. METHODS: A healthy, trained runner (30y male) completed an incremental test to exhaustion on a cycle ergometer, followed by an incremental test on a treadmill that progressed from walking to running. Leg blood flow and cardiac output were determined using the single bolus thermodilution technique. Throughout exercise, metabolic variables, femoral and venous pressures and temperatures were measured continuously, with regular sampling of arterial and venous blood. RESULTS: The participant reached a greater peak oxygen uptake during running relative to cycling (74 vs. 68 mL·kg-1·min-1). Peak limb blood flow was greater at peak running exercise (10.9 vs. 10.5 L·min-1); however, a greater peak cardiac output was observed during cycle exercise (28.6 vs. 30.2 L·min-1). The ‘beat phenomenon’ was apparent in femoral artery measures while running, and thereby produced large swings in leg conductance (62 - 90 mL·min-1·mmHg-1 @ 70 % VO2peak). Average leg vascular conductance was greater during walking relative to similar intensity cycling (36 vs. 25 mL·min-1·mmHg-1 @ ~25 % VO2peak) and remained greater during high intensity running (92 vs. 72 mL·min-1·mmHg-1 @ ~80 % VO2peak). CONCLUSION: We present the first direct measure of leg blood flow and conductance in a running human. Our findings corroborate several assumptions about leg blood flow during running compared to cycling. Crucially, we show that using thermodilution in running exercise can be completed safely. Natural Sciences and Engineering Research Council
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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 | 0.002 | 0.006 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".