The doctor is in

Marc Rowe sent this to me from the British Journal of Sports Medicine. If you can translate the medical-ese it says the tai chi master didn't lean forward or back, he kept his center. What do you know?

Br J Sports Med 2003;37:339-344 doi:10.1136/bjsm.37.4.339


Original article
Kinematic and electromyographic analysis of the push movement in tai chi

+ Author Affiliations
Department of Sports Science and Physical Education, The Chinese University of Hong Kong, Hong Kong

Correspondence to:
 Ms Chan, Department of Sports Science and Physical Education, Kwok Sports Building, The Chinese University of Hong Kong, Shatin, NT, Hong Kong;chan_suk_ping@alumni.cuhk.net

Accepted 16 September 2002

Abstract

Background: Tai chi is a form of exercise derived from the martial art folk traditions of China. The force used in tai chi includes different principles of mechanical advantage. No studies on the kinematic features of tai chi exercise have been published.
Objective: To analyse the kinematics and electromyographic characteristics of tai chi.
Methods: An experienced tai chi master was asked to perform a sequence of basic movements: ward off, roll back, press, and push. The movements were videotaped and digitised using a motion analysis system. Electromyographic activities of the lumbar erector spinae, rectus femoris, medial hamstrings, and medial head of gastrocnemius were recorded by surface electrodes. The push movement data were analysed.
Results: The medial hamstrings and medial head of gastrocnemius muscle groups maintained low activity, with higher electromyographic values in the lumbar erector spinae and substantially higher ones in the rectus femoris during the push movement. Both concentric and eccentric contractions occurred in muscles of the lower limbs, with eccentric contraction occurring mainly in the anti-gravity muscles such as the rectus femoris and the medial head of gastrocnemius. The forward and backward shifts in centre of gravity (CG) were mainly accomplished by increasing and decreasing respectively the joint angles of the bilateral lower limbs rather than by adopting a forward or backward postural lean. The path of the CG in the anteroposterior and mediolateral component was unique, and the sway or deviation from the path was small. The master maintained an upright posture and maintained a low CG (hips, knees, and ankles bent) while travelling slowly and steadily from one position to another.
Conclusion: The eccentric muscle contraction of the lower limbs in the push movement of tai chi may help to strengthen the muscles.