new ways to use a bike for exercise...
http://68.media.tumblr.com/aa344dc0e070df5bb9db2b92dede3da5/tumblr_o0eye29f3u1t8ivmgo1_500.gif
http://68.media.tumblr.com/9be61c6b41cce6be20990d003eba031e/tumblr_o0eye29f3u1t8ivmgo3_500.gif
thtp://68.media.tumblr.com/30d8fac1b10d0266302873a43f891489/tumblr_o0eye29f3u1t8ivmgo6_500.gif
http://68.media.tumblr.com/392cc147dc74f35ebefaff62e0fbc157/tumblr_o0eye29f3u1t8ivmgo8_500.gif