Aerobic conditioning, anaerobic conditioning, strength, power, speed, mobility, structural balance, agility — among any other factor you can think of.
Periodization is the intelligent organization of your training phases so that you can guarantee everything you’re doing in the gym is logically and progressively transforming you into a better hockey player. The science behind periodization runs extremely deep, and the reality here is that full textbooks have been dedicated to this topic alone. Periodization is almost always how great coaches separate themselves from good coaches. Good coaches have their athletes do “hockey exercises” and “hockey workouts”, but they lack the big-picture viewpoint of structuring your training to meet a precise endpoint.