I started going to a gym two months ago, planning to start biking soon. I decided to try a spinning class, in part out of curiosity. The instructor was a cyclist, the bikes Lemonds with SPD pedals. I found I worked harder than I would have on the fancy trainer bikes (virtual tours on screen) and that the routine had sufficient changes to keep it interesting. My first spinning class occurred before I started riding my 35 year-old bike. The gym and spinning classes definitely made it easier to start biking (30 miles week 1, 60 miles week 2, 38 & 23 mile rides to start week 3). This is faster than I could have ramped up without the classes. I am still taking the classes once a week, although twice I've had to bail before the end of the hour.

I have not been taking any rides over 5 miles on the three days I do gym (I work very near my limit) or a fourth day when I do the spinning class. I am not sure I could do the weights right after the spinning class - maybe I will test this one of these weeks if it rains on the spin class day.

Big picture (for me) is the spinning class can be very hard-core training and something that would be hard to duplicate on the road.