a) Cov ntaub qhwv ntsej muag dav dav kom tau raws li qhov xav tau ntawm kev cob qhia ntawm ntau pawg.
b) Nrog lub zog siab engineering yas barbell raj tiv thaiv npog.
c) Nrog limiting mechanism kom muaj kev nyab xeeb ntawm tus kws qhia.
d) Qhov dav ntawm qhov kev hloov pauv yog qhov dav ntawm tus neeg siv lub duav sib koom ua ke, muab rau tus neeg siv kev paub zoo dua thiab meej stimulation ntawm cov leeg nqaij.
e) Kev sib txuas ruaj khov tuaj yeem ua kom zoo rau cov neeg siv kev cob qhia.