That's going to depend a lot on the design of the treadmill. Generally higher end models have some spring in them while the cheap stuff you can buy at Walmart i

That's going to depend a lot on the design of the treadmill. Generally higher end models have some spring in them while the cheap stuff you can buy at Walmart is hard as a rock. For myself, I rarely run on the treadmill, I speed walk at an incline. It takes longer to get as good of a workout as running would but I usually watch videos while on it anyway which is more difficult when running due to more noise.