A century of exercise physiology: effects of muscle contraction and exercise on skeletal muscle Na+,K+-ATPase, Na+ and K+ ions, and on plasma K+ concentration—historical developments
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Bibliographic record
Abstract
Abstract This historical review traces key discoveries regarding K + and Na + ions in skeletal muscle at rest and with exercise, including contents and concentrations, Na + ,K + -ATPase (NKA) and exercise effects on plasma [K + ] in humans. Following initial measures in 1896 of muscle contents in various species, including humans, electrical stimulation of animal muscle showed K + loss and gains in Na + , Cl − and H 2 0, then subsequently bidirectional muscle K + and Na + fluxes. After NKA discovery in 1957, methods were developed to quantify muscle NKA activity via rates of ATP hydrolysis, Na + /K + radioisotope fluxes, [ 3 H]-ouabain binding and phosphatase activity. Since then, it became clear that NKA plays a central role in Na + /K + homeostasis and that NKA content and activity are regulated by muscle contractions and numerous hormones. During intense exercise in humans, muscle intracellular [K + ] falls by 21 mM (range − 13 to − 39 mM), interstitial [K + ] increases to 12–13 mM, and plasma [K + ] rises to 6–8 mM, whilst post-exercise plasma [K + ] falls rapidly, reflecting increased muscle NKA activity. Contractions were shown to increase NKA activity in proportion to activation frequency in animal intact muscle preparations. In human muscle, [ 3 H]-ouabain-binding content fully quantifies NKA content, whilst the method mainly detects α 2 isoforms in rats. Acute or chronic exercise affects human muscle K + , NKA content, activity, isoforms and phospholemman (FXYD1). Numerous hormones, pharmacological and dietary interventions, altered acid–base or redox states, exercise training and physical inactivity modulate plasma [K + ] during exercise. Finally, historical research approaches largely excluded female participants and typically used very small sample sizes.
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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) | 0.000 | 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 it