From the College of Physical Education, Shandong Normal University, Jinan, China.
All correspondence and requests for reprints should be addressed to: Meng Ding, PhD, College of Physical Education, Shandong Normal University, Wenhuadong Rd 88, Jinan 250014, China.
Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the author or by any individuals in control of the content of this article.
