4To WWK, Wong MWN. Factors associated with pain back pain symptoms in pregnancy and the persistence of pain 2 years after pregnancy. Acta Obstet Gynecol Scand ,2003,82 : 1086-1091.
9The North American spine society's adhoc committce on diagnostic and therapeutic procedures.common diagnostic and therapelltic Procedures of the lumbosacral spine.Spine,1991,16:1161.
10Kan Raan Paa M,Laaksomen D,Taimela S,et al.Age,sex and body mass in dex as determinants of back and hip extensor fatigue in the isometric Sorensen back endurance test.Arch Phys Med Rehabil,1998,9:1069-1075.
