Plasticity and function of human skeletal muscle in relation to disuse and rehabilitation: Influence of ageing and surgery.
Level 5 - mechanism / opinion, no new human data
Narrative review and thesis synthesis summarizing multiple human experimental and clinical disuse/rehabilitation studies
What was done
The author synthesized findings from human experimental models investigating disuse, aging, and recovery. Models included elderly patients with unilateral hip osteoarthritis (chronic disuse and post-operative rehabilitation comparing resistance training, neuromuscular electrical stimulation, and conventional rehab) alongside healthy young and older adults undergoing short-term unilateral lower limb immobilization (4 and 14 days) followed by reloading.
What was found
The abstract reports no exact numeric values, percentages, or sample sizes. Chronic disuse in older adults caused reductions in muscle strength, quadriceps cross-sectional area (CSA), myofibre area, architectural parameters, and neuromuscular activation, with side-to-side deficits in specific strength (MVC/LCSA) and rapid force capacity (RFD/CSA). At 4 days of immobilization, reductions in myofibre area were comparable between young and old adults. At 14 days, young adults lost more muscle mass, while older adults experienced greater impairments in neural function and RFD. During reloading, older adults showed blunted myofibre hypertrophy, smaller increases in satellite cell count, and persistent myostatin mRNA elevation compared to younger adults. In post-operative elderly patients, resistance training increased maximal strength, muscle size, and IGF-I mRNA splice variants, whereas neuromuscular electrical stimulation or conventional rehabilitation alone did not.
Why it matters
These findings clarify how aging modifies cellular and neuromuscular responses across the time course of disuse and reloading, highlighting resistance training as a necessary rehabilitation component to reverse disuse-induced muscle wasting and weakness in older adults.
Limits
The abstract is a synthesis of multiple sub-studies that omits exact participant counts, baseline demographics, effect sizes, and confidence intervals. Specific rehabilitation protocols, training loads, and long-term functional clinical outcomes beyond immediate recovery are not detailed in the abstract text.
Cited by
- supports Local limb immobilization in younger adults induces muscle atrophy and creates an anabolic resistance response similar to that seen in older adults.