I just came back in from a planned six-mile walk. I wore a backpack that I'd filled with 13 kg of assorted weights, padded out with a fleece, to try and simulate how I was a few months ago.
I've been doing the six miles without problems recently, but today I only managed three miles before I called quits. The knees and hips didn't like it one little bit.
Wow! I don't want to put those kilos back on again. I hope I can keep remembering how horrible it feels to carry all that extra weight around. Now for the next 13!!