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 rehabilitative health-care services provide HealthSouth (NYSE: HLS) jumped more than 12% in intraday trading on news that the company had raised its fourth-quarter earnings outlook.

So what: As we dive headfirst into fourth-quarter earnings season, we're going to see not only a barrage of earnings reports, but also companies adjusting previous guidance before they deliver full results. It was the latter that put rocket boosters under HealthSouth's shares today after the company made a relatively quiet announcement on Friday that it is boosting its fourth-quarter outlook for earnings per share from $1.57 to $1.62 to a range of $1.67 to $1.70. The move elicited some positive coverage from Wall Street analysts, including a higher price target from Jefferies.

Now what: A key theme for HealthSouth has been reducing leverage and getting the company back on more sound financial footing. Management has been doing a commendable job with that thus far, and improvement in the company's operating results will only aid in those efforts. Investors will get a closer look at how well the company has been doing when it reports full results in mid-February.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his Motley Fool CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.