Most table tennis players label topspin shots into several categories such as: loop, block or smash. However, modern attacking players have developed an offensive block called an active block. Active blocking is a combination between a block, loop and counter loop. It is best used off-the-bounce against a slow to medium speed loop.
Watch in this http://www.youtube.com/watch?v=kwbcgOPxx8w&feature=fvsr as Kenta effectively uses active blocking to stop his opponents’ attack and take control of the table.
Kenta wants to make the opening attack, but often his opponent attacks first. By using active blocking, he is able to keep the pressure on. Once his opponent hits a softer loop, Kenta moves in for his hardest attack.
Steps to Learning Active Blocking

1. Start by first developing a controlled forehand block without any backswing
2. Slowly add more follow-though crosscourt, still without any backswing
3. Add some topspin by brushing over the top of the ball while keeping the ball in front of your body
4. Focus on adding 10% spin and 5% speed to the oncoming ball