From hell's heart, I stab at thee!
A small case is secured to the prisoner's back with a harness. The needle/spike (21) is retracted into the case, but is spring-loaded outward into the back of the prisoner.
A clockwork-like ratchet and pendulum mechanism holds the needle retracted against the spring using a winding key (again, similar to clockwork). However, running motion rocks the pendulum up and down which incrementally drives the needle into the back of the prisoner with the ratchet. This should hurt, I would think, and would probably "persuade" me from running very far. Presumably the pendulum wouldn't be sensitive enough to react to just walking, or the officers could periodically re-wind the mechanism. Rough and effective, but of questionable acceptability under various Conventions. And also a literal stab in the back.
"Device for preventing prisoners from escaping" US Patent 536,979 (1895)
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