"I was questioning the assumption the original poster was making, that she was losing actual muscle in one week. Doesn't seem very likely to me."
Agreed, unless you are ill, you don't usually lose (or gain) much muscle in a week. Longer term, I would use strength as a measure of muscle changes, though if you aren't doing any kind of resistance exercise this is not a good measure.
"But OHS halved the weight of the cement bags some years ago because many people could not lift the original ones"
INn NZ, we can buy pre-mixed concrete in bags as small as 15kg, but plain cement is usually still sold in 40kg bags. As for the reason for some countries dropping the weight of bags, this is as much a reflection on how we are deteriorating in our general fitness as it is the safe limit of a bag of product X. In NZ, they have recently decreased the weight of pellet fire fuel from 20kg to 15kg as many people can't even manage 20kg. Of course, unlike cement, some elderly people don't have a choice, so a choice of bag weights seems a good idea. But smaller bags of anything cost more, per kg, than larger bags. I was also being a little tongue-in-cheek. I don't know many women that can handle a 40kg bag of cement, and thus we bat our eyelids at young men to do it for us...well some of us anyway.
To me, functional strength encompasses more than just lifting a particular weight. Many gym junkies can lift a lot of *weight*, but still put their backs out when lifting much less weight in the real world. Their functional strength is poor unless the weight has a handy little bar to grip, and they can lift it in a straight plane in a pre-practiced pattern. And *most* people I now have very poor overall core strength, even some that can lift heavy weights. Personally, I still like to play judo, which requires core strength combined with good technique to do well. But really it would be good for the OP to clarify what kind of fitness/muscle/strength/stamina goals they are concerned about. My take-home message, and the only reason I posted that photo, was to emphasise the point that you don't need animal proteins to be strong, and even as a female on a strict vegan diet, strength is not out of reach with the right diet and training program. People who slag off proteins such as soy, fail to understand that it is only potentially limiting in methionine, but only if you are getting the minimum suggested protein intake. If you are eating LOTS of soy protein (or most other plant proteins), it is a non-issue. You will get plenty of methionine. But everyone is different. There are ways to incorporate strength and endurance into a single weight program. Good old Arnold S. did this with his German 10 x 10 method. That's a 100 reps per exercise, without reducing the weight on any rep. It's brutal and painful, so not for the feint hearted, but is do-able. I prefer to separate my strength and endurance activities. For me, I may weight train 3 x week, with sprints the other 2 days, and go hiking on the weekends. Throw in some judo twice a week, which is strength, speed and endurance, and it works for me. Whatever fits the lifestyle (and body type) is the best program...