After a long period of benign conditions, rumblings of discontent are beginning to be felt in the U.S. bond market, according to an article published today by Standard & Poor’s Ratings Services.

“Many of the factors that contributed to the bullishness in prior years–such as low inflation, surging corporate profitability, and an accommodative monetary policy–are now poised to weaken from previous levels,” notes head of Standard & Poor’s Global Fixed Income Research Group Diane Vazza.

“Continued volatility in the bond market could create pressure points for distressed credits, which have substantially benefited from benign financing conditions,” she adds. The article says volatility in the U.S. speculative-grade market intensified in April and May, but appears to be retreating in June.

A rising distressed ratio would signal increased urgent need for capital by those most in need and potentially act as a precursor to higher defaults – if accompanied by a credit crunch, S&P notes. Over the long term, it adds, movements in the distressed ratio correspond well with trends in the speculative-grade default rate, with a peak in the distressed ratio generally signaling a peak in default rates a year later.