Effects of Respiratory Alkalosis on Phosphocreatine Kinetics During Moderate-Intensity Plantar Flexion Exercise
Bibliographic record
Abstract
Hyperventilation-induced respiratory alkalosis (R-ALK) causes a leftward-shift in the oxyhemoglobin dissociation curve, and, presumably, a reduced availability of oxygen (O) in the active muscle. PURPOSE: To examine the effects of R-ALK on muscle phosphocreatine (PCr) kinetics following a step increase in work rate from rest to moderate-intensity exercise (MOD). METHODS: Male subjects (n = 6; age, 24 ± 4 yrs; mean ± SD) initially performed an incremental ramped plantar flexion (PF) exercise protocol (∼ 1 W/min, 0.5Hz, 40°ROM) to determine the work rate corresponding to the onset of acidosis (intracellular pH (pHi) threshold (IT)). The IT was then used to determine the MOD workload (75% IT) for the experimental trials. The subjects performed PF exercise during a control (CON) and R-ALK (30 breaths/min, PETCO2 ∼ 15 mmHg) condition. The exercise trials consisted of 20 min rest, 6 min MOD, and 10 min recovery. Trials were repeated 3–5 times in each condition. Muscle PCr and pHi changes were measured using 3-tesla 31P-magnetic resonance spectroscopy (time resolution = 6 s) using a 4X9 cm surface coil placed on the lateral gastrocnemius. Individual trials were ensemble-averaged to produce a single data set for each subject in each condition. The PCr response was modeled using a mono-exponential equation. RESULTS: Resting pHi was greater P < 0.05) in R-ALK (7.06 ± 0.02) than CON (7.02 ± 0.02), however, during exercise there was no difference in pHi between conditions. At rest, [PCr] was not different between CON (40 ± 4 mM) and R-ALK (40 ± 4 mM). The time constant of PCr degradation (?PCr) during transition from rest to MOD was similar in CON (33 ± 12 s) and R-ALK (36 ± 16 s), however the relative PCr amplitude was greater (P < 0.05) in R-ALK (28 ± 4%) compared to CON (25 ± 5%). CONCLUSIONS: Although the rate of PCr hydrolysis was not affected by R-ALK, the increased amplitude of the response is consistent with the hypothesis that greater degradation of PCr is required to drive oxidative phosphorylation when O2 availability is reduced.
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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".