Originally Posted by
Bmach
I highly doubt that anyone will lose 5lbs of muscle in 3 weeks. IMO.
As a hospital-based physician and fitness nerd, I don't doubt it at all. Here's a pretty good review of what happen to muscle when oldies stop moving.
https://www.ncbi.nlm.nih.gov/pmc/art...MC3276215/#R13
"...
data from the only study to examine older adults suggests that the loss of lean tissue in healthy older adults during bed rest far exceeds the losses experienced by their younger counterparts. Specifically, Kortebein et al. observed a 0.95 kg loss of lean leg mass (0.63 kg·wk-1
) following just 10 days of bed rest in otherwise healthy older adults [13]. Assuming the rate of muscle loss is somewhat linear during the initial days/weeks of bed rest, this represents an approximate 3 to 6-fold greater rate of muscle loss in bed-ridden older adults."
The study subjects in reference 13 were healthy volunteers, mean age 67, maintained on a normal diet. The full text is paywalled, but I can send it to anyone who's interested.
The OP was not on complete bed rest, but the acute phase of recovery from significant injury involves systemic inflammation and a catabolic state, where resources are diverted to healing and anabolic processes, such as amino acid deposition in muscle, is effectively halted.
Most old people are losing muscle at a slow, but measurable, rate anyway and the only way to maintain it is resistance exercise and lots and lots of dietary protein.