A method of estimating the maximal oxygen uptake of an individual on the basis of heart rate data, biometric data, biomechanical data, and geophysical data is described. These data can be collected as the individual engages in activities requiring various levels of exertion, without modifying those activities from the ordinary manner in which they are performed. In particular, in some embodiments the method described here obviates the conventional need for a laboratory setting when estimating maximal oxygen uptake and the method can be applied to estimate maximal oxygen uptake under more natural conditions than conventional testing protocols requiring treadmills or stationary ergometers typically permit. Furthermore, it is described how such estimates of maximal oxygen uptake can be used to estimate other quantities of interest, including fat and carbohydrate metabolism, lactate production, and water and electrolyte loss during exercise.
