There are many types of fitness and each have different training demands. It sounds like you body is used to low sets, medium to high reps. Someone further up this thread suggested more sets and higher weights. I second that. Also try more metabolic conditioning stuff. Mix it up and get out of your comfort zone. That's the only way to grow. Above all, jack up the intensity. Intensity is more sets, more weight, less rest, more frequency, etc. You might want to try some Crossfit type workouts.