Here is a curved treadmill that takes your HIIT to the next level. The Signature Fitness SF-S2 Sprint Demon Curved Treadmill is ideal for high intensity walking and running. It is motorless but helps you burn 30% more calories than a motorized treadmill. It has 7 levels of resistance and multiple hand grips. Its digital display shows your calories, heart rate, and speed.
This treadmill has flexible slats and goes easier on your joints as your exercise.