Disuse-Induced Muscle Loss and Rehabilitation: The National Aeronautics and Space Administration Bed Rest Study
Bibliographic record
Abstract
Objectives: The time course and magnitude of atrophic remodeling and the effects of an acute rehabilitation program on muscle atrophy are unclear. We sought to characterize bed rest–induced leg muscle atrophy and evaluate the safety and efficacy of an acute rehabilitation program. Design: Prespecified analysis of a randomized controlled trial. Setting: Single-center urban hospital. Patients: Adults (24–55 yr) randomized to 70 days of sedentary bed rest. Interventions: The 11-day post-bed rest rehabilitation program consisted of low intensity exercise and progressed to increased aerobic exercise duration, plyometric exercises, and higher intensity resistance exercise. Measurements and Main Results: Upper (rectus femoris, vastus lateralis, quadriceps, hamstrings, adductors) and lower leg (medial gastrocnemius, lateral gastrocnemius, and soleus) MRI scans were obtained once before, nine times during, and three times after bed rest to assess muscle cross-sectional area. The magnitude and rate of muscle atrophy and recovery were determined for each muscle. Nine participants completed 70 days of sedentary bed rest and an 11-day rehabilitation program. A total of 11,588 muscle cross-sectional area images were quantified. Across all muscles except the rectus femoris (no change), there was a linear decline during bed rest, with the highest atrophic rate occurring in the soleus (–0.33%/d). Following rehabilitation, there was rapid recovery in all muscles; however, the quadriceps (–3.74 cm 2 ; 95% CI, –7.36 to –0.12; p = 0.04), hamstrings (–2.30 cm 2 ; 95% CI, –4.07 to –0.54; p = 0.01), medial gastrocnemius (–0.62 cm 2 ; 95% CI, –1.10 to –0.14; p = 0.01), and soleus (–1.85 cm 2 ; 95% CI, –2.90 to –0.81; p < 0.01) remained significantly lower than baseline. Conclusions: Bed rest results in upper and lower leg muscle atrophy in a linear pattern, and an 11-day rehabilitation program was safe and effective in initiating a rapid trajectory of muscle recovery. These findings provide important information regarding the design and refinement of rehabilitation programs following bed rest.
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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 | 0.003 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".