Effect of Prolonged Bed-rest on Thigh Muscle Atrophy

Bed-rest is an epidemic assignment for patients under specific medical treatments or certain conditions such as surgical or orthopedic ones. Extended bed-rest and immobilization can lead to muscle atrophy and bone loss. On the other hand, these two medical conditions take place in long-term space flights. Scientists simulate organ immobilization and long-term space flight conditions by prescribing bed-rest for humans to be able to measure and investigate the amount and the percentage of their muscle atrophy using magnetic resonance imaging over different time intervals. In this study, a model for simulating muscle atrophy caused by strict bed-rest over time has been presented by considering the theory of area growth, through adopting a multiplicative decomposition of the deformation gradient into the growth and the elastic part, and by introducing a simple evolution equation. The simulation of the muscle atrophy process was granted utilizing a model written as a finite element code, separately for several different lower limb muscles, including Semitendinosus, Semimembranosus, and Biceps muscles at different periods. Subsequently, the accuracy of the simulation results was compared with the experimental results.