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 Under Armour (NYSE:UAA) flexed their muscles in a big way today, finishing the trading session with a 12% gain after Under Armour beat analyst expectations on both top and bottom lines, before the opening bell.

So what: The fitness-apparel company posted revenue of $454.5 million for its second quarter, a 23% year-over-year improvement that came in above Wall Street's $449-million consensus. Under Armour's earnings of $0.16 per share was also $0.02 better than the consensus. This momentum was good enough for Under Armour to raise its fiscal-year revenue projection to the $2.23 billion to $2.25 billion range, which now bests the Street's $2.24 consensus. Earlier projections in the $2.21 billion to $2.23 billion were not up to snuff in that regard.

Now what: Under Armour has certainly been a great competitor in many investors' portfolios, and shares are once again nudging toward all-time highs. However, the company is hardly cheap with a 60-plus P/E, and the growth of Under Armour's share price has, by now, far exceeded the growth of its earnings over the past five years (and over shorter time frames, as well). Investors should pause to consider whether or not the company can really muster enough earnings growth to catch up with its share price. If not, it could be time to put this stock on the bench.

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