What drives spin?

Ji-Soo Woo

Last updated on 23-Jan-2011 11:47:57 PM

Hi Alois

In answer to an earlier question of mine, you said that 70% of spin from a serve comes from the wrist and 30% from the arm.

That got me thinking about other shots...namely the forehand and backhand loop. I know giving precise percentages to these things is meaningless but roughly speaking, how would you break up where spin is generated in these strokes?

Forehand Loop

Elbow (i.e. speed with which you close the angle of the elbow as you make contact with the ball) A %

Shoulders (i.e. basically speed with which you move the whole arm up over the ball) B%

Waist (i.e. speed with which you turn your torso through the shot) C%

Backhand Loop

Wrist (i.e. the breaking of the wrist as you make contact with the ball) D%

Forearm/Elbow (i.e. the speed with which the forearm moves from the elbow join) E%

Shoulder (i.e. the speed with which the whole arm moves from the shoulder) F%

Thanks!

Ji-Soo

and Alois Rosario said...

Hi ji-Soo,

An interesting question as always.

I think we need to think about what generates spin. It is the brushing contact and the speed of the contact. So for the serve the wrist is moving fastest.

For the forehand topspin I think the forearm is probably moving the fastest with a little help from the wrist. This is because the wrist is moving more in a sideways direction to generate the spin and doesn't have as full a range of movement as for the serve. The backhand topspin is also interesting. It probably follows the forehand topspin model closely.

The shoulder and waist and alos upper arm all add to the speed that you are able to move the bat. They will all have their part in generating more speed of contact.

Table Tennis strokes are a summation of forces. As you said it is difficult to put percentages on it but here is my feeling.

Forehand and Backhand topspin Wrist 30%, Forearm 50%, Waist & shoulders 20%. These are just feelings and certainly not backed up by any data. Maybe someone out there has some data they can share.

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Comments on this question

Ji-Soo Woo commented...

on the 09-Oct-2008 07:55:52 PM

Thanks for your thoughts Alois

I just wanted to confirm, when you say forearm 50% you are referring to the acceleration from the elbow (since you referred to shoulders separately)?

Thanks, this makes sense to me because a very good player (who used to hit with Jeff in his Canberra days) once critiqued my forehand loop against backspin and commented I use too much shoulder and not enough elbow.

Ji-Soo Woo commented...

on the 10-Oct-2008 09:51:34 AM

I'm surprised to read that wrist is 30% for both forehand and backhand. I would have thought the wrist was critical for the backhand (the biggest factor) but minimally important for the forehand. You don't see people cocking their wrists right back on their forehand loops as they do preparing for a backhand.