gradient analysis along a route

[Jonathan_D]

I am considering a potential new cycle route and I want to be able to do some analysis of the slope/gradients along the route.

I've produced the profile graph below, but now want to be able to highlight (on the same graph if possible), for example, where the route is over 4% gradient for 50m along the route.

Can anyone explain how to do this? I've tried with a few of the spatial analyst and slope tools but havent been able to get anything from them. I haven't got much GIS expereince though, so any pointers will be very appreicated. Thank you.