It turns out that it's basically the same as normal exercise, except that the vibrations make it a bit harder. That's why the class is so short; it's just 15 minutes, including rest breaks. There are three settings on the machine: vibration speed (rpm), duration (seconds), and strength (high/low). The duration would typically be 30/45/60 seconds (they may in fact be the only possible settings), so this system really is designed for short bursts. Most of the exercises were cardio (rather than resistance), and they reminded me of aerobics. For instance, we started out by stepping up onto the machine and back down to the ground (like step aerobics). The trainer told us to go faster, so I did, but he then told me to save some energy for later on!
The next exercise was similar, except that we kept one foot on the plate, and swung the other leg back and forth, bringing the knee up high and then stretching the leg out behind. (We did a minute on one leg, then had a rest and did a minute on the other leg.) This involved a certain amount of balance, which is a bit more tricky while the ground is shaking. However, this is a situation where I'm seeing the benefit of losing weight: it's now actually possible for me to lift my knee above my waist. I've also found that some of my old clothes fit again, e.g. gym shorts and swimsuit, and it's nice not to feel that I'm fighting against my own clothing when I move.
After that, we had to spring from side to side. The idea was to stand with my left foot on the ground (next to the machine) and my right foot on the left hand side of the plate, while holding the handles of the machine with both hands. I would then jump up and land with my left foot on the right hand side of the plate and my right foot on the ground. We went back and forth like this for a minute: I was a bit worried that I'd sweep my own foot out from underneath me, but I managed not to trip myself up.
Next was press-ups, with feet on the floor and hands on the plate. We had to do press-ups for 20 seconds, then hold our position (chest just above the plate) for 10 seconds. There's a countdown timer on the machine, and it felt a bit like the bomb clocks you see in films that take ages to tick through the final few seconds. The bigger problem was that I only managed to do one proper press-up, then I had to rest my knees on the ground instead. (The trainer advised me to lift my feet up and cross them over, to make it slightly harder.) So, I need to practice press-ups at home; I already knew that, but if I can't do them on the floor then I won't be able to do them on the plate.
We then did something that's similar to press-ups, but rotating around a different axis. We rested both forearms (elbow to hand) on the plate, then tilted so that the left arm and leg were up in the air. Again, we repeated this for 20 seconds and held the position for 10 seconds, then repeated it for the right side.
After that we were all basically slumped on the floor, so the trainer ended the class. Still, I think it all went fairly well, and now that I know how the machines work I can use them on my own (outside a class).
After that, I went along to Pizza Hut for lunch, since they have Happy Hour between 14:00 and 18:00. This costs £4, so it's cheaper than a buffet (I'd usually pay £6.49 + extra for a drink). The trade-off is that you get smaller portions, but it actually worked out quite well. When I go to an "all you can eat" buffet, I feel that I need to refill my plate a couple of times in order to get value for money, and I usually wind up feeling a bit ill afterwards. After today's meal, I didn't feel hungry, and I was happy to walk home afterwards (about a mile). So, that all worked out nicely.