EFFECTS OF GUAYAKI YERBA MATE CONSUMPTION ON COGNITIVE PERFORMANCE IN COLLEGE STUDENTS MUSCLE FATIGUE REDUCES ACTIVE STIFFNESS
Bibliographic record
Abstract
J.D. Cooper, G.E. Privett, A.W. Ricci, D.M. Callahan University of Oregon, Eugene, OR Muscle stiffness impacts, flexibility, force production, and soft tissue injury risk. Past studies suggest fatiguing exercise reduces whole muscle passive stiffness, but the origins of fatigue-induced compliance are unclear. Furthermore, similar measures of stiffness in actively contracting muscle are non-existent. Evidence from pre-clinical studies of skeletal and cardiac muscle suggest fatigue modifies the muscle protein titin, and these modifications reduce mechanical stiffness. However, these possibilities have not been explored in human skeletal muscle. Therefore, the PURPOSE of this study was to evaluate how acute fatigue modifies active cellular mechanics in humans and to test the hypothesis that fatigue reduces stiffness while not affecting active force generation. METHODS: Two males and two females completed repeated maximum voluntary knee extensions with their dominant leg until task failure. Immediately following, the volunteers underwent a bilateral percutaneous needle muscle biopsy of the Vastus Lateralis, providing a fatigued and non-fatigued sample. Individual fibers were dissected from the biopsy samples and mounted to a permeabilized single fiber force measurement apparatus (Aurora Scientific, ON Canada). Active stiffness was measured by submerging single fibers in activating solution (pCa 4.5) and measuring peak isometric force at steady-state. Immediately after, fiber length was briefly shortened then returned to original length. Stiffness was defined by the resultant change in force per unit length change (mN/mm). RESULTS: Fatigue reduced stiffness in activated single fibers (12.9 ± 4.8 mN/mm and 11.1 ± 4.8 mN/mm; p < 0.01, n= 175). There was no main effect of sex, nor a sex/fatigue interaction. There was no difference in active isometric tension between non-fatigued and fatigued fibers (139.3 ± 29.3 mN/mm2 and 136.2 ± 32.0 mN/mm2). CONCLUSION: Our findings suggest fatigue reduces active stiffness, but not isometric force generating capacity, at the cellular level. Active stiffness reduction may be due to intracellular protein mechanisms. Therefore, these data could influence future research into the mechanisms explaining fatigue induced musculotendinous stiffness reduction. This work was supported by the Wu Tsai Human Performance Alliance.
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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 | 0.000 |
| 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) | 0.003 | 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".