Through the use of partial derivatives it is possible to determine a rate-of-change with consideration to height and weight as dependent variables in the body surface area function of Du Bois. This is useful in medical environments where health is in question and when utilized amid engineering practices, efficiency of the heart as a pump and kidneys as a filter can be directly related to body size. This is achieved by the process of: partially deriving, substituting into the appropriate formulas, and comparing initial values with final values.

Research here supports the assertion that there is a direct link between body size and organ efficiency in individuals rather than having to draw upon further connections from: body size to health risks, health risks to organ impact and thus organ efficiency. This narrows the parameters needed to estimate health and therefore gives a valuable foundation for improving the overall wellbeing of an individual.