I was reading on T Nation an article about deadlifts... it suggested trying to do 20reps at 60% of your 1rm in 10 minutes (in sets of whatever you can handle etc)
doesn't sound too hard but I tried it last night... warmed up on 60kg, did a couple of sets at 80kg, then went to 100kg to do 20 in 10min (I've never tried a 1rm so I just guessed at the weight)... did sets of 5, 5, 3, 3, 2, 2
....... and was thoroughly farked by the end of it... had trouble with all my lifts for the rest of the session except for lifts where I was lying on my back (which I don't do much of as I prefer to stand to do most exercises)
just goes to show how important your core is to 90% of stuff you do in the gym