Research
Mixed
Disuse atrophy exhibits fiber-type specificity, with Type I (slow-twitch) fibers atrophying faster and to a greater degree than Type II (fast-twitch) fibers during prolonged disuse.
During long periods of immobilization, your slow-twitch muscles (often in the calves and postural muscles) may lose size and strength faster than your fast-twitch muscles. This is why calf atrophy is often noticeable early in bed rest or casting.
ModerateSupportsMEDIUM confidence
loss of fiber size and force was reported in the soleus and gastrocnemius muscles with the order of atrophy (greatest-least) being: soleus type I > soleus type II > gastrocnemius type I > gastrocnemius type II
Why this rating
Supported by multiple studies, though some shorter-duration studies (<14 days) did not show this specificity.
Source
Human Skeletal Muscle Disuse Atrophy: Effects on Muscle Protein Synthesis, Breakdown, and Insulin Resistance—A Qualitative Review
Supreeth Rudrappa et al. · Frontiers in Physiology · 2016
DOI 10.3389/fphys.2016.00361
narrative_reviewCited 186×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Skeletal muscle disuse (immobilization, bed rest, or unloading) causes rapid muscle atrophy primarily through a significant reduction in muscle protein synthesis (MPS), while muscle protein breakdown (MPB) remains largely unchanged or is not the primary driver.Good
- Muscle disuse induces muscle-specific insulin resistance (IR), which accelerates muscle mass loss, particularly in individuals with pre-existing Type 2 Diabetes.Good
Related findings · Mixed
- Bariatric surgery (VSG and RYGB) is the most effective and sustainable treatment for obesity, producing marked and sustained weight loss that non-surgical interventions cannot match.Strong
- Severely protein-deficient diets (2–3% energy) induce lean body mass loss and metabolic imbalance, whereas adequate protein intake (0.66 g/kg/d minimum) is a prerequisite for maintaining muscle, bone, and physiological function.Strong
- For patients with Class III obesity (BMI >39.9 kg/m2), metabolic bariatric surgery (MBS) is significantly more effective than any currently approved medication, with BilioPancreatic Diversion (BPD) showing the highest estimated weight loss.Strong
This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →