Perhaps you've heard of the X3 Bar. It's a small bar that you can attach heavy duty weight resistance bands to. The creator John Jaquish claims that weights are a ''waste of time'' because you can build muscle with his bar through variable resistance.
The idea is that you are weak at the bottom of your lifts and strongest as you get closer to the top.
By using variable resistance, you are able to take advantage of your body's biomechanics and get in the resistance you need at your strongest points but saving your joints on the weak points.
The Dr. does make a good point. Many people that have been lifting heavy for years do have some kind of nagging pain. The stronger you get, the more load you're putting on your joints.
I laughed at the system for a long time. I still don't own it, but I ordered one that was 5 times cheaper and is similar. I will admit that I had the best shoulder press set of my life. It not only fried my muscles, but I was able to get a full range of motion without any pain at all. It just has a totally smoother feel than free weights.
I'm not claiming that it can give you the muscles of an Olympic bodybuilder. But I'm starting to believe that for the average person who isn't trying to get extremely muscular, this system might be better because not only does it really challenge you, but your joints feel better than when you do free weights. You're pain-free.
Now, my disclaimer is that this is just my opinon right now. I could be missing something. It is interesting to know that gyms are so huge, with so many different machines. It's hard to believe that something like a bar with bands can provide you a similar benefit but with much more convenience. But after doing it, I admit it gives me a different kind of workout and it's tough and pain free.