| 摘要 |
<p>A tubular piston element 16 is displaceable within a tubular cylinder element 12 by gripping the respective handles 20 and 14. Apertures 18 provide for controlled displacement of water into and out of the chamber defined between the tubular elements 12 and 16. The resistance to movement by the user is variable according to the number of apertures 18 which are closed. <IMAGE></p> |
