Disclosed herein are techniques and systems for evaluating exercise performance of a user of a fitness system by utilizing one or more intelligent sensors, including at least one camera-based sensor configured to detect image data of the user. The fitness system may include a stationary exercise device, a memory to store personal information about a user, and a processor to generate a set of exercise rules based, at least in part, on the personal information about the user. The fitness system may also include one or more sensors to monitor a physical state of the user, and a fuzzy system to generate an evaluation for the user based, at least in part, on i) the set of rules and ii) output from the one or more sensors. The fitness system may thereby provide real-time, constructive feedback regarding the user's exercise performance based on the sensed data.