Shorting means a live wire touching neutral or ground with no electrical load - very high current is drawn and to stop the wires overheating and catching fire the fuse acts as a safety device.
If your treadmill really does have a "short circuit" then it should be investigated.
If there is not a short then something is taking more current than it normally should - I don't know treadmill electronics but from what you say I would expect a short of some sort and the cause to be either in the power supply to the control electronics - the motor or motor control circuit - the motor start/run capacitor if it has one.
If the fuse is popping when the treadmill is in use then it may be due to excessive current because of a mechanical overload - something binding in the moving parts overloading the motor.
In either case too much current is being drawn - do not be tempted to use a higher rated fuse to solve the problem - you may get a fire if you do.
Peccavi, April 2010
