Source: Sams Teach Yourself C++ in 24 Hours (5th Edition)
This book is dedicated to my dad, who’s currently teaching himself something a lot harder than computer programming: how to walk again after spinal surgery. Through the many months of rehab, you’ve been an inspiration. I’ve never known someone with as much indefatigable determination to fix the hitch in his giddy-up.
What exactly are they talking about?
Giddyup!1 is a command typically directed at a horse or similar animal to encourage it to start moving. In a transferred sense it can be a prompt addressed at other people or even more simplified the process of getting in motion.
A hitch is something that doesn't go smoothly, both literally and figuratively. A jerking motion, something stuck or tied down.
So a hitch in the giddyup indicates a physical / motoric problem in general, often a sign of age or injury.
1 As it's a transcript of an oral command, other spellings occur.
