May 6, 2008 - By Krista Conger
Master Chen Xiang, an 18th-level tai chi master, can generate a force 14 times his body weight when making a strike. His movements were studied by researchers.
Tai chi is an ancient Chinese martial arts form, often seen in this country when groups of people in outdoor parks perform graceful arm-and-body movements in unison. So what was a tai chi master doing last month in a lab at Lucile Packard Children's Hospital?
He was the object of attention at the Motion & Gait Analysis Laboratory, a service within the hospital's Johnson Center for Pregnancy and Newborn Services that specializes in helping children who have cerebral palsy and other movement disorders.
'Tai chi represents optimal body movement, honed over centuries,' said laboratory director Jessica Rose, PhD. 'We're always interested in getting baseline biomechanical measurements from people who are highly skilled in particular types of movement. Although many people don't realize it, every one of those slow moves you see in the park can be transformed into really fast strikes.'
Rose, assistant professor of orthopedic surgery, together with orthopedic surgeon Amy Ladd, MD, teaches a class at the School of Medicine on the 'Anatomy of Movement.' She became interested in studying tai chi movements in the gait lab after several of her students brought up the idea.
Understanding both the slow and the fast movements of tai chi can advance the lab's primary mission, which is to diagnose the underlying causes of walking problems in children. The tai chi master was just the latest person to have reflective markers fastened to his legs and joints to record precise movements at the lab. Measurements of muscle activity, balance, joint movement, forces acting on the joints and energy expended during walking create a complete picture of a patient's gait or, in this case, a master's 'strike.'
During his first visit from Beijing last year, Master Chen Xiang, an 18th-level tai chi master, astonished Rose and her students by the amount of force that can be generated by a highly trained tai chi master during a strike. She and her colleagues calculated that the full-strength blow delivered a floor reaction torque of more than 14 times his body weight while accelerating his striking arm from 0 to 60 mph in less than three seconds.
'It seems to be an almost perfect example of translating the angular momentum of his body into the linear momentum of the strike,' said Rose. 'The power begins first in the trailing foot and is then rotated through the body in a super-fast pivot, then transferred to the striking arm.'
These calculations and observations attracted the attention of robotics specialist Oussama Khatib, PhD, professor of computer science, who heads Stanford's artificial intelligence lab. They seemed to confirm his theory that these types of spiral movements may be a particularly efficient way to generate force in a small sphere of space.
Lab staff fasten reflective markers to measure movement of the master's legs.
In addition to continuing their study of tai chi strikes, the researchers expanded the scope of their inquiries based on some preliminary studies performed on Stanford's own resident tai chi master, Shu Dong Li. Together with Dennis Grahn, PhD, senior research scientist in biology, and two professors of radiology, Scott Atlas, MD, and Gary Glover, PhD, they used thermography and functional magnetic resonance imaging to measure biophysical changes that occur during the process of 'focusing the chi.' In Chinese martial arts and Eastern medicine, chi, or qi, represents a life force or energy that can be focused through meditative concentration.
'It was fascinating,' said Blase Iuliano, a research associate on the study. 'We could see Master Li's hands just light up in the infrared image.' But that wasn't all. While the researchers were remarking about Li's ability to warm the skin of his hands by about two degrees, he volunteered to cool them as well. 'And in a matter of moments, he reduced the temperature by about six degrees,' said Iuliano. Furthermore, focusing the chi in this way corresponded with the activation of specific areas of the brain associated with movement and feeling in the hands.
This type of voluntary control over the peripheral vascular system is rare. It's possible that teaching children how to harness this ability could help them control chronic pain, manage disease and reduce stress. Recent studies from other institutions have suggested tai chi training can promote calmness and relaxation in middle school children and improve pulmonary function in children with asthma.
It's not just kids who can benefit from tai chi. Other studies at Stanford and elsewhere have shown that adult practitioners gain balance, musculoskeletal, cardiovascular and immune benefits.
In April, a multidisciplinary team of researchers from Packard Children's and the medical school orthopedics, radiology, biology and computer sciences departments collaborated to conduct similar tests on Chen, which he agreed to undergo.
'He is curious to see if we can define 'chi,'' said Rose, 'and we are intrigued by his agility and the immense force he generates, the unusual thermal regulation and brain activity. Increasing our understanding of the way he moves can add to our understanding of motor deficits, robotics and rehabilitation-device design for children for whom just walking across the floor is a struggle.'
Stanford Medicine integrates research, medical education and health care at its three institutions - Stanford School of Medicine, Stanford Health Care, and Stanford Children's Health. For more information, please visit the Office of Communications website at http://mednews.stanford.edu.