Spin, Spin, Spin.

I goto spin classes 3X/week. On Sundays, I hit the dreadmill right after the class and do a 40 minute run.
Is it a brick? I sure as heck think so!

you'll get a range of answers.

my 2 copper coins of the realm:

Maybe.

I've been in spin classes where my heart rate wouldn't hit 120 with what the instructer says. One instructer I do like will have us climb for 50 minutes. HRM's blowing up. I back it off and keep it in at the bottom of my zone 4. I do a 30 min tempo run on the dreadmill at a 3.0 incline after that.

I spin once a week as 'speed work' on the bike. its helped me. your mileage may vary.

In my book, IT'S A BRICK!

Spinning is a great way to train in the winter months when it's too cold to ride outdoors.

I think spinning is a GREAT workout..I have gotten so into it I am planning on becming an instructor this summer! and heck yeah, that is definitely a BRICK!

Spinning not only can be a great workout, it often is more social and enjoyable that an outdoor ride. But the instructor is key. I also wear a heart monitor to make sure I'm in my target zone.

Also, I don't remember where I read it, but there was an article that stressed what to do and not do during spinning. (has anyone else seen this article?)Bascially only do techniques that you'd use in the real world. For example no running (quick cadence, low resistance climbing), no "hovering" (shifting weight back keeping your butt just off the seat), and avoid jumps. The risk of injury isn't worth the acrobatics. Try to have your spin session focus on skills that acutally translate into racing skills. So use common sense.

There is an article like that on the tri-newbies online website. I found it very helpful as the spinning instructors at my Y are not cyclists themselves.