Why are people so sensitive or ticklish on the soles of their feet? 

Why is a foot rub the most pleasurable (or most painful) part of a massage?

The sole of your foot has a zillion nerve endings in it.  So do the joints of the foot and ankle.  That makes this part of your anatomy extra sensitive.

There’s a reason we’ve got all those extra nerve endings in the feet.

Did you ever hear an advertisement for an SUV that shifts its load from wheel to wheel in slippery conditions?  Our brain performs a far more sophisticated version of the same process all the time. When you stand or walk, your brain needs information from the foot in order to control your balance and posture.

A research article from 2007 describes how adjusting the foot improves your brain’s control of balance and posture.

The study concerns field hockey players, but the findings apply to anyone, athlete or not.  The researchers recorded how people stood on their feet: what parts of the foot carried the most weight.  The athletes received a basic adjustment of the joints of the foot.  Afterward their weight-bearing pattern had shifted.  There was also improved brain control of posture.

I’ve had many experiences working with foot problems of dancers, athletes, and ordinary people too.  Although the immediate reason people come to see me is a sprain or tendonitis, I palpate the joints of the foot and usually find that the underlying problem is in the motion of the joints.  Fortunately, this can be fixed.