The difference between gym running and outdoor running lies in the different running slopes. Treadmills can provide stable slopes, but the slopes of ordinary roads are not exactly the same. Treadmill can run for a long time but not on ordinary roads, because the outdoor running posture is not strictly controlled, and the air time is longer without propulsion. The air time comes from the vertical jumping force, and the propulsion force comes from the back swing and back pedal made by the lower limbs.

Running on an ordinary treadmill, because the conveyor belt will automatically run, the runner's body relies more on the strength of jumping up when exerting its strength, and the forward strength is less than that of outdoor running. This is also the main reason why people who have been running on the treadmill for a long time will feel a little uncomfortable and tired when they first start running. Long-term road running, people who don't run on the treadmill, have a short adaptation period when they first start running on the treadmill.

Running on a treadmill and adjusting the slope to 1-3 degrees can basically simulate road running. There are different opinions on how much the treadmill slope can be raised to simulate road running to the greatest extent. I think you can choose according to your personal situation. For runners with poor physical strength, 1-2 degrees can be increased, and for runners with good physical strength, it can be increased by 2-3 degrees. When the slope is low, the speed can be increased by about 15% to simulate road driving.