Learn the block: return topspin in a controlled way with a closed blade and a short movement. With step sequence, milestones and the most common mistakes.
The honest answer: the block is a holding stroke with little or no backswing in which you use your opponent's pace to control the ball. That is how English federation coaches define it [1]. The Swiss Federal Office of Sport lists it with the counter-hit and the finishing stroke among the strokes without spin [2]. You do not hit, you hold the racket out.
Why is it so difficult? Because against topspin you have hardly any time. In a study with six young players and one coach (supplemented by launching-machine measurements), a ball with topspin of at least 110 revolutions per second reached a point 1 m past the end line about 27 milliseconds earlier than a ball with at most 80 revolutions at the same initial speed. The players' average was 117 revolutions per second [3]. 27 milliseconds is tiny, a fraction of a blink, but for the block it is the difference between control and error.
The block is rated as a beginner stroke but has a hurdle: you need a partner who can play slow topspin. Without one, you keep practising counter-hits on the side.
To put speed in context: in novices, hitting performance dropped sharply from 11.5 m/s (about 41 km/h), and also with higher ball frequency and changing landing points [4]. So ask your partner for a speed at which you can still control the ball.
Stand close to the table, about a forearm's length away, knees slightly bent. That way you have less distance to the ball (practice). The racket is in front of your body, the elbow slightly bent.
Tilt the blade slightly forward-down, it is closed. Against more topspin you need a more closed blade (practice). If the ball hits your open blade, it jumps high and long.
The racket does not go back. It stays in front of the body in the starting position [1] and meets the ball early, shortly after the bounce (practice). The movement is a short counter-hold or holding out. The wrist stays firm, the energy comes from the opponent. Imagine the racket is a door you are holding shut: you do not have to hit against it, you only have to hold it at the right angle. The faster the ball comes, the less you have to do yourself (practice).
You set the trajectory with small things: closing the blade a bit more brings the ball lower, a small push forward gives a bit more speed (practice). Goal for the start: ball diagonally into the middle of the table.
Your partner plays 10 slow topspins: if you manage 8 out of 10 blocks onto the table, you raise the speed slightly. Then 20 blocks in a row, first backhand, then forehand. If you manage both, move on to the forehand topspin. These numbers are practice standards.
The block puts little load on the body. Still, table tennis is not injury-free. Tendon sheath inflammation, strains and sprains are among the most common findings [6]. The evidence is thin. Take breaks when wrist or forearm pull, and have persistent pain checked. This guide explains and motivates, it does not replace supervised training.
Make the racket a wall. Hold it motionless in front of your body and have ten slow topspins played to you without moving. Count how many land on the other side. At first this feels like doing nothing, but it trains exactly the most important thing about the block: setting the racket angle and letting the ball do the rest. Only then do you add a tiny push forward.
The block is a holding stroke with no or very little backswing in which you use the pace of the opponent's ball to control it [1]. It is usually played with a closed blade and is the standard answer to topspin. You hold, you do not hit: the opponent supplies the energy, you supply the angle.
With the counter-hit you actively hit a ball with little spin forward. With the block you use the pace of the opponent's topspin and hardly move [1][2]. The block is more passive and shorter. Because both strokes are classified as spinless, they feel similar. The difference lies in the backswing and in the feed.
Usually the blade is too open or you take a backswing. Close the blade more, hold the racket forward and hit the ball early. Against heavy topspin the blade needs more closing than against light topspin. Test it with ten balls: if the ball gets shorter when you close the blade a bit more, you have found the lever.
Yes, for example the active block with a little more forward movement and the chop block. You learn those once the basic block sits, with 20 balls in a row on both sides. Before that they only add sources of error, without your feel for the angle being good enough.
Forehand Topspin: The Most Important Attacking Stroke in Table Tennis