Learn the backhand topspin: drive from legs and trunk, forearm and wrist in front of the body. With a staged plan against counter-hits and backspin.
The honest answer: the backhand topspin is the attacking stroke on your backhand side. You brush the ball in its upper half forward-up, it gets forward spin [1], and you play all of this in front of the body from forearm and wrist, with drive from legs and trunk. It turns your backhand, which so far only defended, into a point-scoring stroke.
Why does it pay off? In 30 simulated matches of national-level players, topspin was the second most frequent backhand stroke after the push at 31.9 % [2]. And modern top players use it deliberately: a study with 15 elite men examined backhand loops against backspin because they are increasingly seen as an important scoring stroke in the modern game [3].
How hard is it really? For many players the backhand topspin is easier to learn than the forehand topspin because the racket stays in front of the body (experience value). In return it has less reach and needs good timing. Expect weeks to months until it sits against backspin.
Stand a little further from the table than for the counter-hit so you have room to take the racket back (practice). Feet shoulder-width, knees slightly bent, weight slightly forward. The racket is in front of your belly, the elbow loose in front of the body.
Let the racket sink down-back in front of your hip, the blade is slightly closed. The elbow stays forward and acts as a pivot. The upper body turns a small amount towards the playing side. In backhand topspin strokes, racket speed was linked to arm abduction and the rotation of the shoulder girdle towards the playing side [4].
Extend the legs, the trunk rotates slightly, then the forearm shoots forward-up and the wrist accelerates at the end. In 15 elite men, the fast backhand loop emphasised hip-extension torque, the slow one knee-extension torque [3]. In the backhand stroke, shakehand players also rotated the forearm into supination (palm turning up) faster than with the penhold grip [5]. That means: the forearm turns along with the stroke.
Hit the ball in front of the body at its highest point or on the slightly rising part and brush it forward-up. Against backspin you open the blade a bit and hit more upward (practice). Target first: diagonally into the middle of the table, then parallel. Changes of direction depended on early elbow flexion and trunk rotation: cross-court loops needed more trunk rotation than long-line [3].
The racket ends in front of the forehead or the opposite shoulder. Do not brake the swing abruptly, let it run out and then go back into ready position.
Stage 1: 10 out of 10 against slow counter-hits to the backhand. Stage 2: 7 out of 10 against pushes. Stage 3: alternating push and backhand topspin, 10 rallies. If you manage stage 3, you close the chain. These numbers are practice standards.
The backhand topspin loads shoulder, elbow, wrist and the legs. Table tennis is considered low-risk, but tendon sheath inflammation, strains and sprains are among the most common findings [6]. In a study with elite players, fast loops and cross-court strokes loaded the leg on the playing side more in the follow-through phase; the authors see an injury risk there if the braking load gets too high [3]. For you that means: build leg strength, increase the number of strokes slowly and take breaks. This guide explains and motivates, it does not replace supervised training.
Switch deliberately between slow and fast topspin. In the fast loop, hip-extension torque was emphasised, in the slow one knee-extension torque [3]. Play ten slow loops with lots of spin and then ten fast ones. That way you learn both gears. Against real opponents you need both: the slow loop starts the rally, the fast one ends it.
The backhand topspin comes from forearm and wrist in front of the body, the forehand topspin from a large trunk rotation. The backhand has less reach but short paths (practice). Both brush the ball forward-up [1]. If you master both sides, you no longer have to run around the ball and save energy.
Very. In simulated matches of national-level players it made up 31.9 % of all backhand strokes, only the push was more frequent [2]. If you only use the backhand for blocking and pushing, you leave a big part of your attacking options unused.
Both. In a small study (six men and six women), the authors suggest that women can attack backspin with both sides, men rather with the forehand [7]. As a beginner you first need the basics on both sides. If you specialise later, it is about your playing style, not a fixed rule.
Usually the blade is too closed or you hit the ball too late and too low. Open the blade a bit against backspin and hit more upward. Looking at a target instead of at your hand improved backhand accuracy in a study with lower-skilled players [8].
Backhand Serve in Table Tennis: How to Vary Your Service