Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of power transmission products maker Altra Holdings (NASDAQ:AIMC) plummeted 17% today after its quarterly results and outlook disappointed Wall Street. 

So what: The stock has soared over the past year on solid earnings growth, but today's second-quarter results -- adjusted EPS stayed flat on a 3.6% drop in revenue -- coupled with downbeat guidance for the full year is forcing Mr. Market to sober up. On a positive note, gross margin actually expanded 20 basis points despite the slump in sales as management did a good job to reduce costs in the quarter.

Now what: Management now sees full-year EPS of $1.52-$1.64 on revenue of $715 million-$730 million, down from its prior view of $1.75-$1.85 on revenue of $740 million-$750 million. "[W]e expect that the second half of the year will be in line with the comparable period a year ago," said CEO Carl Christenson. "Given the lower-than-expected results in the first half of the year and the lack of any apparent catalyst for significant economic growth in the second half, we are revising our guidance for the full year." When you couple that demand uncertainty with Altra's not-so-cheapish P/E of 25, Fools might want to wait for more of a pullback before jumping in.

Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.