See how Nordic Track machines work in this video.

[patrickcorliss]

40 percent or 40 degrees ?

[MikeDunn]

@patrickcorliss It's 40%.  If you're into math, you take the inverse tan to find the angle. So take the inverse tan of 40% (or .40), and the angle is 21.8 degrees.

[patrickcorliss]

@MikeDunn

Thank you for the math - that's interesting.

I know 45 degrees is half a right angle and that's easy to visualise. The slope of the machine looks close to that 45 degree angle. Hence my question.

Would you agree that the angle looks bigger than 21.8 degrees?

[MikeDunn]

@patrickcorliss Haha, yes, it does look bigger than 21.8 degrees. I was thinking about this, and I suspect it's just an optical illusion. If you check the beginning of the video, it does say 40%. I think this is how the grade or steepness of a hill is usually measured.

Again, if you're into math, the percentage is actually a ratio of how far "up" you're walking compared to how far forward. So a 40% grade (or .40) means you're walking up 0.4 meters for every meter you walk forward.