Develop a Customized Workout Plan for a Fitness Enthusiast

Given a user's fitness level, age, and goals (e.g., weight loss, muscle gain, endurance), develop a customized workout plan that includes a combination of cardio and strength training exercises. Incorporate the user's preferred exercise routine, including any specific preferences for equipment or exercises. Consider factors such as injury history, body composition, and overall health to design a safe and effective workout plan. As of 2026-05-20, provide a 12-week workout plan with a mix of high-intensity interval training (HIIT), strength training, and flexibility exercises. Include a sample workout schedule with specific exercises, sets, reps, and rest times.