NO. Not even remotely close to the arc length for a standard spline, perhaps something computed using the function spline.
Although depending on what spline you are working with, say something computed using cscvn, then it can be interpreted in terms of the distance between consecutive points as a set of straight lines or chords. In that case, there is some relation to arc length. But your question is far too vgue to have any idea what splines you are working with.
Are you trying to compute arc length for a curve?