Based on the context provided, "WOD" most likely refers to "Workout of the Day," which is a common term used in CrossFit to designate the specific workout that participants are expected to complete for that day. Therefore, it can be inferred that Bruno enjoys doing the workout of the day.
While he may enjoy other aspects of CrossFit, such as tracking his performance with a wearable device, following a diet, or seeing his name on a wall of dedication, the phrase "he especially enjoys the WOD" specifically indicates his enjoyment of the workout itself.