Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to train for cross country running [title] Try interval training. [step] Interval training involves alternating between periods (known as intervals) of high-intensity exercise with low-intensity exercise. Switch between sprinting and walking in 2 to 3 minute intervals.

Ending1: Your run can last anywhere from thirty minutes to an hour, depending on the distance you choose. During the high-intensity interval, give the workout as much energy as you can to increase your strength. Ending2: Sprint hard for 3 to 6 minutes every day. Then switch to walking at a safe distance in between your intervals. Ending3: You can run a variety of styles between practice sessions. [substeps] For example, you could alternate sprinting and walking in a 1 to 2 minute pattern. Ending4: Intervals vary in intensity from 10 minutes to 20 minutes for aerobic, half-marathon, or endurance workouts. Between intervals, lengthen distances and complete sprints to lower your chances of injury.

Answer format: ending1/ending2/ending3/ending4