A method of measuring expended energy of a moving body, including providing a first sensor for measuring data of a first part of the moving body; providing a second sensor for measuring data of a second part of the moving body, wherein the second part is moveable relative to the first part and connected to the first part by a first resistive deformable element that is external to the moving body; using the first sensor to make a first measurement and subsequently calculating a global expended energy of the first part relative to a reference frame; using the second sensor to make a second measurement and subsequently calculating a relative expended energy of the second part relative to the first part; and calculating the total expended energy of the moving body by summing the global expended energy with the relative expended energy.