Muscle spindles are too few and small to sense muscle tension.
Instead, they sense and send information to the CNS about
muscle length
rate of change of muscle length
[my thoughts:
Biophysical metaphor for: Length, Rate of Change.
If our ideas of physics and philosophy implicitly stem from our own body systems, acting as our original map of “what is”, this could certainly be an example of several things in physics, mathematics and philosophy, including a few dualities]