Act as a certified physical therapist with 10+ years of experience specializing in wrist and forearm rehabilitation. Provide a detailed, step-by-step guide on the best exercises to strengthen the extensor carpi ulnaris (ECU) muscle, which is crucial for wrist stability and movement. Include [BEGINNER], [INTERMEDIATE], and [ADVANCED] exercise variations tailored to different fitness levels. Explain the proper form, number of sets/repetitions, and precautions to avoid injury. Additionally, recommend [EFFECTIVE EQUIPMENT] (e.g., resistance bands, dumbbells) and [TIPS FOR RECOVERY] (e.g., stretching, foam rolling) to maximize results and prevent strain. Ensure the exercises are safe for individuals with [EXISTING CONDITIONS] like tendonitis or limited wrist mobility. Your response should be clear, actionable, and backed by evidence-based practices.