The Effect Of A Semi-upright Body Position On Oxygen Consumption Kinetics During Submaximal Cycling
Bibliographic record
Abstract
Assessments of cardiac function, including stress echocardiography and exercise right heart catheterization, are typically completed in a semi-upright (SU) cycling position. This position poses a unique hemodynamic challenge and while oxygen uptake (VO2) kinetics during upright (UR) cycling are well known, how exercising in a SU position may influence VO2 kinetics during exercise is poorly understood. PURPOSE: To compare the time required to reach 63% of steady state (tau) between an UR and SU body position during submaximal cycling exercise. METHODS: Twenty healthy individuals (22 ± 3 yr, 50% male) completed alternating sequential five-minute bouts of submaximal UR and SU (40° incline) cycling at 50 W and 100 W on electronically braked ergometers. Starting body position was randomly assigned and counterbalanced (n = 10 UR; n = 10 SU). To explore the rest to exercise transition, the first 50 W stage was used for this analysis. Breath-by-breath VO2 was obtained, and local outliers were removed. Data was linearly interpolated at 1-s intervals, time aligned to the beginning of exercise, and fit with a mono-exponential model encompassing both the cardiodynamic phase I and phase II rise in VO2. Tau and overall gain were assessed along with constituents of VO2 during the final 30 sec of exercise. Data are ∆ from seated rest and reported as mean ± SD. Significance was set at p < 0.05. RESULTS: UR and SU groups did not differ with respect to sex, age, weight, height, and BMI (all p > 0.37). Individuals cycling in a SU position had a lower VO2 gain compared to individuals cycling in an UR position (9.5 ± 2.2 vs. 12.7 ± 1.2 ml/kg/min, p = 0.001). This was due to a reduced increase in minute ventilation (16 ± 3 vs. 22 ± 4 L/min, p = 0.001) and a blunted decrease in the end tidal fraction of expired oxygen concentration (-0.48 ± 0.95 vs. -1.29 ± 0.56 %, p = 0.031). Tau was not different between SU and UR body positions (49 ± 23 vs. 48 ± 23 sec, p = 0.917). CONCLUSION: The overall gain in VO2 was lower in the SU cycling position; however, tau was similar between body positions. This suggests that individuals cycling in a SU position reach steady state in the same amount of time as individuals cycling in an UR position, despite a lower overall VO2. This is an important consideration when interpreting physiological responses in a SU position. Supported by NSERC Discovery Grant.
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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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".