OMG i think you would LOVE bodypump! It's a Les Mills, just google "Bodypump Les Mills" and the website with the class intros and stuff will come up.

The class i do is 60 mins (there is an express for 45 mins i believe too but our gym only does the longer class). It's all done to music with a bar and different weight plates and a step/bench. Each new number indicates a new routine and new music. The class is always laid out the same: warm-up, squats, chest, back, triceps, biceps, shoulders, abs and each area has a new track. The emphasis is on lower weight and lots of reps, rather than heavy weights/low reps. Of each release i'd say 2 or 3 tracks are really hard, and the rest aren't too bad and the emphasis shifts with each new release. The current squats (am trying to remember it all so someone correct me if i'm wrong) is (with the bar resting across the squishy part of the top of your back/shoulders you squat down trying to get the thigh and shin to make a 90degree angle (but no lower, many don't manage that far for the whole track) without letting your knee travel forwards too much - like you're going to sit down on a chair):

*squat down for a count of 4 (mega slowly) and back up for count of 4* x2
*down for 3 up for 1* x4
*down for 2, up for 2* x2
*down for 2, up for 2 then 2 singles (down 1, up 1)* x4 or 6 i think
*singles* for 4
*down then only half way up, working the bottom half* x8
*down for 4, up for 4* x2

You repeat that routine 3 times during the track, once with feet hip distance apart, once with them a little wider and the final time you can choose yourself. It sounds relentless written out but the music keeps you going and you usually get a few seconds in between each set to shake off your legs and stretch your back.

All of the muscle groups are like that, with a routine within repeated 3 times, though sometimes they'll be different, like the triceps one just now you start off as i said above, lowering your bum off your bench with your hands on the edge of it and your elbows bending back so when your triceps are taking your weight, then you hold a plate up above your head, "glue" your upper arms to your ears, and lower and raise the plate behind your head, then you lie back on the bench and use the bar to lift either from arms straight up to bar just over the forehead (you keep the upper arm still and only move the elbow) or up and down with the elbows tucked in tight and grazing the ribs each time. So there are 3 different "things" but within each bit the lifts are the same - up4, down 4, up 3 down 1, singles etc.

It is so fun and there's something inspiring about being in a room of people all lifting weights simultaneously. I only do it for 1 hour a week but already in 4 months i am so much more toned and stronger. My running has improved and i feel stronger and more confident. I'd totally recommend you give it a go. A gym near you almost certainly offers it...

Bx