The present invention provides a solid polymer electrolyte; a polymerizable composition having low viscosity and excellent processability for obtaining the solid polymer electrolyte; and a polymerizable compound having low viscosity, and good polymerizability and stability for use in the polymerizable composition. The first of the jaw members having a knife blade and the second jaw member having a cradle with a cutting cage into which the knife extends. The carbon nanostructures may be converted to the insulating electronic state either before or after a layer containing the carbon nanostructures is formed on a substrate. A control system processes the output signal to determine a magnitude of a peak or trough value of the output signal, where the control system is to process the peak or trough value of the output signal to profile the exercise session.