Are changes in muscular strength following head‐down bed rest independently associated with improved cognitive function in older adults? A secondary analysis of a randomized controlled trial
Bibliographic record
Abstract
Abstract Background Physical inactivity is common among older adults and is a risk factor for cognitive decline. Even a brief period of physical inactivity, such as bed rest due to hospitalization, in older adults has significant negative impacts. Exercise is strategy to counter the negative effects of physical inactivity. Exercise‐induced improvements in cardiorespiratory fitness is associated with improved cognitive function. Less is known regarding the contribution of exercise‐induced changes in muscle strength to changes in cognitive function. Thus, we aimed to examine the independent contribution of: 1) change in cardiorespiratory fitness; and 2) change in peak muscle torque of the lower extremity to changes in cognitive function in a randomized controlled trial (RCT) of head‐down bed rest (HDBR) vs. HDBR with exercise in healthy older adults. Method An analysis of a non‐blinded, parallel‐group, RCT of 22 healthy older adults (11 males and 11 females) aged 55‐65 years. Participants were randomized to: 1) 14 days of 6° HDBR (CON); or 2) HDBR with daily resistance and aerobic exercise training (EX). Outcome measures were taken at baseline and HDBR completion. The Flanker Inhibitory Control and Attention Task measured executive function. Physical fitness measures included: 1) maximal aerobic capacity (VO2max) using a bicycle ergometry test; and 2) knee extension isokinetic muscular strength (KE) using a Biodex dynamometer. We performed two separate multiple linear regressions to determine whether following 14 days of HDBR: 1) VO2max was associated with Flanker score, after accounting for ΔKE; and 2) KE was associated with Flanker score, after accounting for ΔVO2max. Each model was also adjusted for baseline Flanker score and the baseline physical fitness measure of interest. Result At baseline, average Flanker t‐score was 48.33, mean VO2max was 32.527 ml/kg/min, and knee extension strength was 64.472 Nm. VO2max at follow‐up was not significantly associated with Flanker performance (b = 0.232 ± 0.716; p = 0.635; R2 adj. = 0.285). However, greater KE strength was significantly associated with better Flanker performance (b = 2.023 ± 0.389; p = 0.043; R2 adj. = 0.633) at HDBR completion. Conclusion The maintenance of muscle strength even during brief periods of physical inactivity appears to be critical for cognitive health in older adults.
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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 | 0.010 | 0.015 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.009 | 0.010 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.003 | 0.003 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".