IF you have the nerves to capitalize on the downward market, buy TVIX and set a trailing stop loss. It was up over 100% last week until the last positive minute run on Friday that pared it's appreciation to just over 65% end of trading day. Trailing stop loss is key here...you need capitalize on profits and as this is not a long term investment...because once the market heads up, TVIX goes the opposite way.
I've always played it against TQQQ...which is opposite to TVIX. TQQQ is an extraordinary play if the market is going up, which it has been until the past two weeks. Like TVIX, set a trailing stop loss for when the market heads down.
If your trading platform allows you to set up trailing stop losses, or you know how to make use of API's, this is a really good "side" play to capture profit on the way down and the way up.
*BTW, I am not a professional (I just play one on messageboards), so take this suggestion as information only...I can't have anyone's wife (or husband) coming after me because one of you put your kids college fund on the line.