THE EFFECT OF OLD AGE ON PERCEIVED EFFORT AND HEART RATE DURING AN ISOMETRIC FATIGUE TASK
Bibliographic record
Abstract
In addition to age-related changes in the neuromuscular system of aged humans, alterations in the perception of effort can affect the comparative fatigability of old versus young subjects during voluntary fatigue tasks. The elbow flexors of 7 young (24 ± 2y) and 6 old men (84 ± 1y) were fatigued using repeated (3s on, 2s off) isometric contractions at 60% MVC until force was reduced to less than 60%. Time to fatigue was not different between age groups (4–5 min). At rest and at 1 min intervals, measures of neural and contractile function were made. During the fatigue task, ratings of perceived exertion (RPE), using a modified Borg scale (0–10), and heart rate (HR) were recorded. RPE and HR measures were compared between groups at ∼15, 30, 50, 70, 87 and 100% of the fatigue time. Although HR was greater at each time point and demonstrated a larger range of increase in the young subjects, both groups experienced the same relative increase in HR when data were normalized to the age-predicted HRmax. At the end of the fatigue task, HR was ∼62% of the age-predicted HRmax for both groups. Although greater RPE values were reported for the old men at 15% (5.2 vs 2.4) and 30% (6.0 vs 3.7) of fatigue time, there were no age-related differences for the remaining fatigue time. By the end of the fatigue protocol all subjects reported the maximal RPE value (10). Muscie activation, as assessed by twitch interpolation, surface EMG, and the ratio of 50Hz tetanic tension to MVC force at fatigue were not affected by age, suggesting that fatigue was not due to a central limitation. Thus, despite similar relative HR responses in both groups throughout the fatigue protocol, the old men had a greater perception of effort during the submaximal contractions in the first ∼30% of the protocol. However, the differences in perceived effort were not accompanied by age-related impairments in neural and contractile measures at the end of the protocol, suggesting that this initial elevated perceived effort did not influence fatigue during this task.
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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".