Left ventricular contractile function is preserved during prolonged exercise in middle-aged men
Bibliographic record
Abstract
We examined left ventricular (LV) performance before, during, and following prolonged exercise (EX) in 12 healthy middle-aged men [means +/- SE: age = 43.5 +/- 1.9 yr; maximal O(2) uptake (Vo(2max)) = 51.7 +/- 1.5 ml.kg(-1).min(-1)]. Subjects cycled for 120 min at 65% Vo(2max) (75% of maximal heart rate). Two-dimensional echocardiography (ECHO) to determine tissue-Doppler longitudinal myocardial strain and strain rate, LV ejection fraction (EF), end-diastolic (EDV), end-systolic (ESV), and stroke volume (SV) at baseline and after 5, 30, and 120 min of EX and following 30 min of recovery. In addition, hematocrit and plasma norepinephrine (NE) were measured. From baseline to 5 min of EX, there were significant increases in LV longitudinal strain (-23.20 +/- 0.87 to -27.63 +/- 1.07%; P < 0.01), strain rate (-1.50 +/- 0.15 to -2.08 +/- 0.14 s(-1); P < 0.01), and EF (56.3 +/- 2.2 to 77.1 +/- 1.0%; P < 0.05) with continued increases by both at 30 min of exercise vs. SV, EDV, and ESV, which remained constant. After 120 min of EX, HR and NE increased further with reductions in SV, cardiac output, and systolic blood pressure without changes in strain or strain rate. EDV decreased after 120 min of EX (-9.2- vs. 30-min value; P = 0.05) along with a hemoconcentration (baseline = 41.3 +/- 1.0 vs. EX = 45.1 +/- 1.2%; P < 0001) and significant reduction in body mass despite a mean fluid consumption of 1.8 +/- 0.2 liters throughout EX. After 30 min of recovery, LV longitudinal strain was depressed relative to baseline (-23.20 +/- 0.87 to -19.57 +/- 1.21%; P < 0.01). The reduction in LV SV during prolonged EX occurred without changes in the LV contractile state and is likely secondary to reduced LV preload. A reduction in LV contractility despite a reduced afterload following exercise may be due to factors unique to the recovery period and do not appear to contribute to a reduction in SV 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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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) | 0.000 | 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".