Non-Dominant Arm Mechanics in the Serve

Q: What are some of the important considerations for the non-
dominant arm during tennis?

A: This is a topic that comes up frequently during biomechanics
discussions in all sports. In tennis, the role of the non-dominant
arm/hand is more important than one might think. Here’s one great
example illustrated in an email I just sent to London:
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July 2, 2010 (Nadal/Murray Wimbledon Semifinals)

To: Miles Maclagan, Head Coach Andy Murray
C/O Lawn Tennis Association
National Tennis Centre
100 Priory Lane
Roehampton, London SW15 5JQ

Dear Mr. Miles Maclagan & Other Coaches:

Andy Murray is one of the only elite players I’ve ever seen
who throws the tossing arm away and back during the follow
through of his serve and I can prove, in mechanical terms, that
it is a significant disadvantage.

In the vast majority of sports movements leading to asymmetric
impact or acceleration of one body part, the concept of “breaking”
is universally employed. What is “breaking”?

Breaking is easy to notice. In place kicking the non kicking foot plants
abruptly so it can pass its momentum to the kicking leg. In loose or wet
turf, that is why kicks cannot go as far.

In throwing, the kinetic chain passes momentum all the way up the
body starting from the ground. For a one armed throwing motion and
tennis serve, the kinetic chain transfers momentum from the ground,
through the legs, to the torso, then into the arm, hand, and racket.
Each passing its momentum, like a whip, in a snapping acceleration
toward the hand. To pass its full momentum onward, each segment
stops, like a billiard ball hitting a row of others which are touching.

In most serves, and right handed throws, the left arm comes across
the torso to help counter or stop the trunk rotation, thereby sending
more momentum into the arm.

Murray’s left arm does not. It goes away and behind without helping
to stop the trunk rotation. It does not supply any “breaking”, or opposing
motion, to the torso. Mechanically, less momentum passes into the arm.

Andy Murray’s serve is certainly a great one. But at this level of expertise
in any sport, one percent improvement can make a huge difference!

Good luck with all your players.

Sincerely,
TennisDr

Jonathan Bailin, Ph.D., USPTA
Exercise Physiology~Biomechanics~Ergonomics
Sports Medicine & Ergonomics Associates