1. A method comprising, by one or more computing devices: accessing an athletic-performance model of a first user, wherein the athletic-performance model is based on a plurality of sets of action-parameter values of action parameters of the first user, the plurality of sets of action-parameter values being determined based on biomechanical data of the first user performing a plurality of actions of a first action-type and outcome data of a plurality of outcomes corresponding to the respective plurality of actions; determining a current skill level of the first user based on the athletic-performance model of the first user, wherein the current skill level is determined based on a measure of one or more variances associated with one or more action parameters of the first action-type; calculating one or more target ranges of action-parameter values for one or more action parameters based on the athletic-performance model, wherein each target range is based on a measure of probability with respect to the particular action parameters and the outcome data; and generating a report of athletic-performance feedback, the report comprising information related to the current skill level of the first user and the one or more target ranges of action-parameter values.