Two bodies have I, though both joined in one. The more still I stand, the quicker I run. What am I?

Common Wrong Answers
“A clock”
While a clock tracks time, it does not have two bodies that are joined in one, nor does it have the characteristic of standing still to run quicker.
“A candle”
A candle does burn down over time and can be seen as a measure of time, but it does not consist of two distinct bodies and does not fit the phrasing of standing still to run quicker.
“A pair of shoes”
A pair of shoes does consist of two bodies, but they do not measure time or have the specific qualities described in the riddle.
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