You can actually trade your coins for USDT at Bittrex. It is a token supposed backed by 1 USD.
1 Tether (USDT) is worth 1 dollar, so you can for example, sell 1 BTC for 4350 USDT and rebuy when the price goes down without needing to transfer money between your bank account and the exchange.
But I would be careful, they seem to be shady at the moment. Check the links: