Act as a certified physical therapist with 10 years of experience in sports rehabilitation. Provide a detailed guide on the best exercises to strengthen the extensor carpi radialis muscle, including [BEGINNER], [INTERMEDIATE], and [ADVANCED] variations. For each exercise, explain proper form, recommended sets and reps, and common mistakes to avoid. Also, suggest [EQUIPMENT] that can enhance effectiveness (e.g., resistance bands, dumbbells) and [MODIFICATIONS] for individuals with wrist discomfort. Emphasize safety and progressive overload principles.