Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to keep muscle mass [title] Modify your training routine. [step] Regardless of why you had to cut back or stop your training routine, there are still exercises you can do to help you maintain your strength. If time is an issue, consider doing a more complete circuit 1-2 times a week.

Ending1: [substeps] Jumping jacks may be particularly effective, but try to make sure you aren't straining yourself at all during the circuit or you might seriously injure yourself. Ultimately, exercise is about building muscle mass. Ending2: If you had to stop training because of an injury, keep working the uninjured areas of your body. A doctor or physical therapist may be able to help you figure out appropriate exercises to maintain muscle without aggravating your injury. Ending3: If you don't feel like you have what it takes to continue developing muscle while you workout, see your physician to rule out a medical issue. [substeps] For women, workouts that increase resistance or strength in the abs can help ensure you maintain more muscle mass. Ending4: After you have reached your target level, you may try exercising more, as well. [substeps] Try walking or running in place for 30 minutes every morning or two or three mornings throughout the day.

Answer format: ending1/ending2/ending3/ending4