I'm now doing bar squats. There is a foam pad I put on the bar. It evens out the weight so my spine does not touch the bar. Works well, I did 3 sets of 6 reps of 95 pounds easily. No neck pain. So I'm going to start upping the weight. I'm being very careful with my form. My knees ached a little, but not too bad. I don't do anything that hurts them, but I think a few temporary aches may just be a part of life for now.
I also now know a pound of muscle is 600 calories. To add 1 pound that is 20% fat, you need 1200 calories plus workout and repair energy. Let's say that is 2000 calories per pound. To add 10 pounds in a month, that is 660 calories per day.
Most people's muscle fiber composition is 25% slow twitch, 50% intermediate, and 25% fast. You can train the intermediate ones to become more like the fast or the slow twitch fibers, over the years. Low reps build strength not only by stimulating the fast twitch, but by stimulating the intermediate to become like the fast twitch.
What I don't know is whether slow twich muscles can access muscle glycogen, and whether fast twitch muscles can burn fatty acids. I've heard conflicting reports.
The more lean you are, the more of your energy will come from muscle instead of fat when you diet. Testosterone and exercise can help the ratio in your favor, but eventually it becomes very hard to have a high muscle to fat ratio in your body. That is why dropping below 9% is hard for many people. Anyone can drop from 30 down to 15%, unless their hormones are really out of wack. If you want to lose weight, make sure your testosterone levels are in the normal range first, or you may just burn muscle.