Steep trail > trail > roadrunning > cycling. Cycling CAN be very good, but very difficult to sustain it as there are too many downhill sections that let you rest.

Pull ups, lats/abs workout

Now, one only needs to do the trail or steep trail occasionally to keep those muscles in shape for balance and brain training on WHERE to place your feet so one doesn't turn your ankles, sprain your knees, and fall on your face, the rest can be roadrunning, cycling, basketball, swimming(fins), raquetball.

I have it easy. I have 10 acres with a 100 foot deep ravine in it. I have a 1/3 mile loop, 1/2 mile loop and trails abutting our property taking me to the top of Grand Ridge and Tiger Mountain. It used to have awesome single track mountain biking until the housing went in, now the trails are just ok for that. Those living near the Issaquah "alps" have it easy like I do.

Everyone else? Stair Stepper