Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to switch from treadmill running to outdoor running [title] Increase your treadmill's incline. [step] Your treadmill is completely flat, while most outdoor running surfaces are not. To help prepare your body for the difference, you can practice by running on an incline on your treadmill.

Ending1: [substeps] The incline makes it easier to adjust your speed. You should be able to run comfortably for 8 to 12 minutes on an incline that is higher than your normal speed. Ending2: You'll need to adjust your position so that your body is making the degree difference, then gradually lower it a bit more. The goal is to allow your legs to be planted on the ground without raising your body into the air. Ending3: Elevation, like the elevation of a mountain, will vary depending on the type of exercise you're doing. [substeps] If you are running on gravel and rock surfaces, you should switch to a treadmill with higher incline. Ending4: [substeps] An incline of 1-2% closely simulates running outdoors. Program your treadmill so that it adjusts incline throughout your run, if the treadmill you use has this feature available.

Answer format: ending1/ending2/ending3/ending4