The first thing to understand is that Work Done = Force * displacement in the direction of the force.
Well, your legs aren't lifting the bag so the arms are exerting an upward force on the bag. So when you are walking the forces exerted by the leg is perpendicular to the force on the bag, so no...
Homework Statement
Given f(x) = e^{-ax^2/2} with a > 0 then show that \^{f} = \int_{-\infty}^{\infty} e^{-i \xi x - ax^2/2} \, \mathrm{d}x = \surd\frac{2}{a} = e^{-\xi^2/2a} by completing the square in the exponent, using Cauchy's theorem to shift the path of integration from the real axis...