It can be done very long under certain conditions and with medical supervision http://www.abc.net.au/science/articles/2012/07/24/3549931.htm http://www.abc.net.

It can be done very long under certain conditions and with medical supervision http://www.abc.net.au/science/articles/2012/07/24/3549931.htm http://www.abc.net.au/science/articles/2012/07/24/3549931.ht...