Reduced H-reflex gain in soleus during isometric plantar flexor and dorsiflexor muscle contractions in old adults
Bibliographic record
Abstract
The modulation of the Hoffmann (H) reflex amplitude during agonist and antagonist muscle contractions provides relevant information on the neural control of leg muscles but remains largely unknown in older adults. This study investigated the H-reflex gain in the soleus muscle at rest and during plantar flexor (PF) and dorsiflexor (DF) muscle contractions performed at 10%, 20%, and 30% of the maximal electromyographic (EMG) activity (EMGMVC) in 12 young (23–35 years) and 12 old adults (61–76 years). The reflex gain was measured as the slope of the relation between H-reflex amplitude and background EMG activity. The stimulation intensity was set to evoke at rest an H reflex in the ascending phase of its recruitment curve preceded by an M wave (5%–10% of its maximal amplitude; Mmax). During PF contractions, the H-reflex amplitude increased with the increase in contraction intensity in both groups with a greater reflex gain ( p = 0.024) in young (1.2 (0.5)% Mmax/% EMGMVC) than older adults (0.7 (0.4)% Mmax/% EMGMVC). During DF contractions, the H-reflex amplitude decreased in both groups, with a more negative reflex gain ( p = 0.009) in young (−6.8 (2.8)% Mmax/% EMGMVC) than older adults (−2.7 (4.0)% Mmax/% EMGMVC). The decrease in H-reflex amplitude was linearly associated with the increase in tibialis anterior EMG in both groups. The present study showed a smaller reflex gain in older adults in soleus during submaximal PF and DF contractions, suggesting a decreased ability to adjust the excitatory afferent inputs during PF contractions, and to modulate reciprocal inhibition during DF contractions.
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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".