Chair, and lower-limb exercise system

Abstract

A chair includes: two coxal bone support balloons that support two coxal bones respectively; and a sacral bone support balloon that supports one of a sacral bone and a coccygeal bone. The two coxal bone support balloons are configured to be able to rock relative to the sacral bone support balloon. In this configuration, the movability of a sacroiliac joint between the two coxal bones and the sacral bone is improved, and therefore, the mechanical stress on a lumbar region joint, on which a load increases in compensation for an insufficient movability of the sacroiliac joint, is curbed, so that a low back pain is relieved.

What is claimed is: 
     
         1 . A chair comprising:
 two first support portions that support two coxal bones respectively; and   a second support portion that supports one of a sacral bone and a coccygeal bone, wherein   the two first support portions are configured to be able to rock relative to the second support portion.   
     
     
         2 . The chair according to  claim 1 , wherein the two first support portions are configured to be able to rock relative to each other. 
     
     
         3 . The chair according to  claim 1 , further comprising:
 a chair body; and   two elastic coupling portions that couple the two first support portions to the chair body respectively, wherein   the two first support portions are configured to be able to rock in a pitch direction and a roll direction due to elastic deformation of the two elastic coupling portions.   
     
     
         4 . The chair according to  claim 1 , wherein at least one of the two first support portions and the second support portion is configured such that a position of the at least one of the two first support portions and the second support portion is able to be adjusted depending on a physical constitution of a user. 
     
     
         5 . A lower-limb exercise system comprising:
 the chair according to  claim 1 ; and   a lower-limb exercise apparatus with which a user performs a lower-limb exercise in a state where the user is sitting in the chair.