Force' of tai chi master

Tai chi master Chen Xiang performs tai chi movements while a motion analysis test is being
conducted at the Motion and Gait Analysis Laboratory in Palo Alto on April 30, 2007.


Stanford researchers record 'optimal
force' of tai chi master

Jessica Rose, an orthopedic surgery professor at Stanford, could not believe
her eyes. Tai chi master Chen Xiang, sensor balls taped to key body joints, was
demonstrating palm, elbow and fist strikes so fast - and with such force - that
the sensors kept flying off his body. And then she glanced at her computer screen, where Chen's movements were mirrored by an animated stick figure.

Like a light-footed dancing skeleton, the figure's grace was undeniable. And
frightening. The explosive power of the strikes was stunning - 400 pounds of
force generated by Chen's body accelerating from 0 mph to 60 mph in 2.8
seconds - faster than any Lamborghini out on the street. This level of power
was a first for her lab. It's also just plain unusual. In its mainstream form,
practiced by millions looking to boost their health, tai chi moves typically are
performed in slow motion.

What Rose recorded in her lab this week, for the first time ever, she believes,
was a biomechanical document of optimal force generation. (Some might call it
pure chi - a.k.a. energy. Think "Star Wars": "May the force be with you.")
Chen's demonstration, conducted at the Motion and Gait Analysis Laboratory at
Lucile Salter Packard Children's Hospital, will serve as another example of a
human performing at its peak and it will be used by Rose and her colleagues
to paint a more detailed picture about how the body moves, and why.

Chen, one of China's best martial artists and a revered master in the tai chi
style he practices, was in Rose's lab purely by happenstance. A friend of
Rose's also happens to know the man organizing Chen's weeklong Bay Area
visit, and he knew immediately that Rose would be eager to bring Chen in.
Not only did Chen oblige, but he also showed charming modesty and humor
about the experiment, laughing when those sensor balls went flying and
gamely dressing in non-traditional tai chi garb: red lycra leggings and a red
cotton T-shirt lettered with the name of the tai chi academy in Beijing where he
teaches.
In-depth view
Although Chen's performance awed his impromptu audience at Stanford, Rose
said, what the recording devices divine will be far more important. Chen's
lightning-fast movements will be compared to a computer's projections of a
human's ideal biomechanical movement, as well as those of a tai chi novice,
potentially revealing detailed and nuanced information about the heights that
the very controlled thought behind tai chi can propel the body to achieve.
Tai chi is a martial art that begins with cultivation of the mind, learning to
discard everything except the thought of moving energy within the body, to
nourish it and bring it to full health and, if necessary, to defend it. Various
schools of tai chi have developed their own ways of training the body, but the
aim is always to keep the joints relaxed to allow a free flow of chi.
What Chen offers, Rose said, is "an example of a highly refined movement
which may be as close as we can get to biomechanically optimal movement
patterns."
He is also, she added, demonstrating a basic law of motion: force equals
mass times acceleration. "No one turns mass into force as well as tai chi
masters," she said. Chen has perfected the art of putting the entire mass of his
body into the impact, accelerating at a rate that makes that force even more
extreme