Interactive Forum March 2012: Sam Stosur's Kick Second Serve

[gzhpcu]

Rod Cross wrote a recent article on the physics of the kick serve with some interesting points: http://twu.tennis-warehouse.com/lear.../kickserve.php

[julian1]

The ratio

I'm not remotely an expert, but with Stosur's serve clocked at up to 120 mph, and typically 110-115 mph, I don't know what ratio you're seeking. Now "in tennis" is tough. Ryan Harrison has a lot of kick at 130 MPH, as just one example, but on the WTA I don't think anyone gets close to Stosur's kick. That's a primary reason WTA players do far worse defending their second serves than ATP players do IMHO i.e. it's extremely difficult to attack del Potro's second serve at 85 mph.

Stosur's downside seems to be predictability and variety.
.

The ratio is
the velocity of the ball divided by the number of rotations per sec

[jimlosaltos]

yeah ...

The ratio is
the velocity of the ball divided by the number of rotations per sec

Well, yes, but since she hits at up to 120 mph is he saying she should hit with higher velocity, which seems unjustifiable, or is he saying she should hit slower serves?

Or is he saying she doesn't get enough spin (since others say she has the most kick on the tour that doesn't make much sense to me either).

So, what is the criticism exactly?

[DougEng]

Rod Cross wrote a recent article on the physics of the kick serve with some interesting points: http://twu.tennis-warehouse.com/lear.../kickserve.php

Nice find! Great article! Rod does excellent work. However, Rod apparently made an error at the start by saying a kick serve needs to be 100 mph. For example, Stefan Edberg regularly served a kick on his first serve at 85-100 mph. Cross corrects himself at the end of the article saying it's possible to serve a kick at below 80 mph. I suspect a "fingerfehler."

An excellent point is the extra spin applied to the ball on a higher toss. Rod points out a toss 3 feet above contact allows a vertical velocity of 9.5 mph or 780 rpm more spin than a toss at the contact point. Howard Brody also used to argue for a higher toss to add spin. Vic Braden argued for a lower toss to allow accurate of contact point. My feeling is that few players mishit the ball on the 2-3 foot drop so it's better to go with Brody/Cross than Braden. In addition, loading must occur in a shorter time frame with a low toss. I don't think many players can generate significant ground force on a low toss, and would benefit from a higher toss. Hence, almost every touring pro tosses at least 12" higher than contact (average is maybe 18-24" above contact or that's the same as the ball drop).

[stroke]

Nice. I noticed in watching video of Dougherty's student Naomi Totka that she finishes even higher than opposite hip. And I do think her signature "sick kick" is powerful yet totally relaxed, spin-loaded and no depth with very sharp angle all on purpose. I saw Michael Llodra, another lefty, do the same thing with great effect in Winston-Salem.

I saw that video also. That girl does have a very nice motion under Pat's tutelage. She is using the technique he teaches in his "Serve MPH" video, which is his latest serve instruction video which kind of builds on, and offers some new ideas to his "Sonic Serve" video.