VIX-linked exchange traded funds have been moving higher along with stocks all week, so something probably had to give.

The usual relationship between Wall Street’s “fear gauge” and stocks was back in place on Friday with the S&P 500 set for a lower open as the Greek drama drags on.

In volatility ETFs, iPath S&P 500 VIX Short-Term Futures ETN (NYSEArca: VXX) rose 4% in premarket trading. It’s important to remember that volatility-linked products follow VIX futures contracts, rather than the spot price. This difference can impact long-term performance based on whether futures traders are pricing in higher or lower market volatility down the road.

The VIX futures ETN was set to rise for the fourth day after climbing nearly 5% on Thursday despite gains in the major U.S. stock indices. The VIX rises when investors are seeking protection in the options market.

A leveraged version, VelocityShares Daily 2X VIX Short Term ETN (NYSEArca: TVIX), has seen trading volume spike in February, suggesting some investors are hedging or speculating on an equity pullback after the strong run from the October low. The S&P 500 is nearing its 2011 highs.

Paul Weisbruch, head of ETF/options sales and trading at Street One Financial, said higher trading in VIX-linked funds and downside protective put buying in major stock ETFs are “likely a reflection of some institutional ‘caution’ regarding this 2012 rally, and also managers taking advantage of benign levels in the VIX and establishing portfolio protection at attractive levels.” [ETF Portfolio Shifts Reflect Risk-On Trade]