Isotonic Power Loss in the Dorsiflexors of Very Old Men
Bibliographic record
Abstract
Muscle power reflects the product of strength and contractile velocity and therefore is likely more susceptible to age-related changes than isometric strength alone. However, there have been few investigations of changes to muscle power with very old age, particularly in the isotonic (constant load) contraction mode. PURPOSE: To contrast the effect of age on isometric dorsiflexor strength and isotonic dorsiflexor power. In addition, we investigated the loss of power during a brief fatigue task. METHODS: Eight young men (26 ± 5 y) and eight very old men (84 ± 3 y) performed maximal isometric dorsiflexion contractions (MVCs). Subsequently, all subjects completed a maximal (i.e., as fast as possible) isotonic load-velocity relationship (25° range of motion; ROM) with loads set to 1 Nm (minimum load) and 10, 20, 30, 40 & 50% of their isometric MVC. To assess the influence of fatigue on muscle power, subjects were asked to perform 24 maximal isotonic dorsiflexion contractions at 20% MVC (1 contraction every 1.5 s). RESULTS: In comparison to young men, very old men had a 33% decrease in isometric MVC and an 18–27% decrease in angular velocity, depending on the load. Isotonic power loss with age ranged between 26–50%, depending on the load. There was no age-related difference in the normalized load-velocity relationship (i.e., angular velocities expressed as a percentage of the value obtained at the 1 Nm load). For example, the angular velocity at 50% MVC was ∼45% of the velocity obtained at the 1 Nm load in both groups. All young subjects completed 24 contractions during the fatigue protocol, whereas two of the very old men were unable to complete the full regiment before ROM failed (a decrease >20%). The loss of isotonic power from the first to final contraction was 10% for the young and 30% for the very old men. CONCLUSION: The dorsiflexors of very old men were weaker and slower than those of young men. The combination of these two effects resulted in a dramatic loss (as great as 50%) of muscle power in the dorsiflexors of very old men. Contrary to recent findings in isometric and isokinetic fatigue protocols, very old men were more fatigable than young men with regard to isotonic power. Supported by NSERC and an Ontario Graduate Scholarship
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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".