Every Tuesday, this site takes a look at a training or technology concept that shapes how tennis is played. This week’s follow-on comes from the same behind-the-scenes sequence at the Mutua Madrid Open introduced last week. Jannik Sinner continues to work through a progression of pre-match muscle activation drills using a small yellow weighted ball. If last Tuesday’s takeaway was that I am becoming obsessed with this training tool, this week does nothing to reverse that trend.
The next movement in Sinner’s sequence is what I would describe as a reverse curtsy paired with a groundstroke loading pattern. It is a controlled, deliberate movement that emphasizes the preparation phase of the stroke rather than the follow-through. Given that this appears immediately after a series of weighted ball groundstrokes, that sequencing makes sense. The follow-through has already been trained. This movement isolates what comes before it.
The execution is subtle but purposeful. Holding the small weighted ball in one hand, Sinner begins by pulling the ball back as if initiating a groundstroke backswing. At the same time, he crosses the front foot in front of the back foot, stepping into a loaded position that resembles a closed or semi-closed stance. This “reverse curtsy” position forces engagement of the lower body, particularly the glutes and hips, while maintaining balance through the movement.
From there, he returns to a neutral standing position by returning the front foot back to the side. As he does that, he transfers the ball to the opposite hand with a short, controlled toss to reset the drill and maintain rhythm. The emphasis remains on the loading phase, the coordination between upper and lower body, and the controlled return to the ready position.
The movement is then mirrored on the backhand side. In that variation, Sinner holds the ball in his left hand while his right hand tracks along with it as he rotates into the loaded position. The mechanics reflect a two-handed backhand preparation, reinforcing the shoulder turn, hip loading, and alignment without the need to actually strike a ball.
There are several reasons this is a smart pre-match activation exercise. First, it reinforces proper loading mechanics. Tennis strokes begin well before contact, and efficient preparation is critical for both power and consistency. By isolating the backswing and lower-body positioning, this drill trains the foundation of the stroke without introducing the complexity of timing a live ball.
Second, it promotes balance and stability. The crossing step creates a slightly unstable position that the body must control. That mirrors the reality of tennis, where players are often required to load and hit from less-than-perfect stances. Training that control in a slow, deliberate way builds confidence when the same situation arises at full speed.
Finally, it activates the kinetic chain in a controlled sequence, loading through the legs, engaging the core, and coordinating upper-body rotation, all without rushing through the movement. It is exactly the kind of sequencing players want to feel before stepping onto the court.
As a bonus, it also fits neatly into a broader warm-up progression. After performing more dynamic, full-motion drills like weighted-ball groundstrokes, this movement serves as a reset, reinforcing positioning and control. It slows things down just enough to remind the body what “correct” feels like.
There is also a practical advantage to using the small weighted ball for this drill. Its compact size makes it easy to handle during transitions, and the added weight provides just enough resistance to engage the muscles without creating fatigue. It is a tool that supports both activation and refinement.
This same small yellow weighted ball keeps appearing across multiple exercises, players, and training contexts. That is not a random coincidence. It is safe to say that I am still obsessed with the small yellow weighted ball.
Yellow Weighted Exercise Ball (<- Sponsored Link)
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