Damn, I just did some forced negatives yesterday when I was training my arms, all I can say is wow. I never been this sore for a very long time, which by the way being sore is a good indicator of muscle growth. Also, this is a great way to bring up the intensity of you workouts.
What Are Forced Negative Reps:
Forced negative repetitions are basically when you or your training partner push down on the weight as hard as they can while you try to not let them push you down. Doing forced negative reps forces you to cope with greater resistance, which means more muscle tears, which means more muscle growth for you. Forced negative repetitions should always be done with machines or cables rather then with free weights since it is very dangerous to do it with free weights.
Next time your in the gym try it out and I guarantee you that you will be very sore the next day. If you can handle the pain the following day then you will be a champion in my book, since you will grow some muscles!