Lifting weights in the gym at 10 reps progressing to 1 Repetition Maximum (the maximum weight you can lift once) is ‘intense’ exercise. Going to a circuit class, Zumba class, or step class is a ‘high density’ exercise because a large volume of exercise is completed in a relatively short period of time.
In general, too much exposure to ‘high intensity’ lifting commonly leads to connective tissue injuries, such as joint capsule strains, ligament strain, and connective tissue strain. Too much ‘density’ (volume of weight lifting usually at 10 RM – 30 RM or aerobic intensities) of exercise most commonly causes muscular challenges, such as painful trigger points, soreness from waste accumulation, muscle imbalances, and progressively slower recovery times between workouts.
For ski conditioning we want to focus on intensity, only focusing on density in the power/endurance phase (Phase 5 of the Ski Fitness programme).