Do they mean the same? I mean "cycling uphill" and "cycling up hills"?
Native speaker’s answer
Rebecca
Yes, they basically mean the same thing here! "Uphill" refers to going in an ascending direction up a hill or slope, whereas "up hills" is meant literally - to ascend a hill. Thus, in this context they are interchangeable. Ex: I don't like walking uphill because it makes me sweat. = I don't like walking up hills because it makes me sweat.