The Finish Line Inc. will partner with a private equity firm in hopes of building a dominant position in specialty running that includes a new website called Run.com, the Indianapolis-based retailer announced Friday.

The company also reported strong fourth-quarter earnings boosted by brisk sales of running shoes, but its outlook for a lower first-quarter profit sent shares tumbling.

Denver-based Gart Capital Partners has agreed to invest $10 million in Finish Line's Running Specialty Group, which operates The Running Company chain of 19 stores, and will take over day-to-day operations from its Colorado headquarters. Finish Line acquired the chain last summer.

Finish Line will retain majority ownership of the running endeavor, which hopes to capitalize on the $1 billion specialty running market by acquiring other operators and building a Web experience that combines running advice and a sense of community with shoe and apparel sales. The website is scheduled to launch in the spring.

Finish Line chose to partner with Gart because of the firm's experience quickly rolling up previously independent retail shops, including a joint venture with Vail Resorts Inc. that owns 150 ski shops, Finish Line CEO Glenn Lyon told Wall Street analysts on a conference call.

"Others will join and others will play, but we think we're out there first," Lyon said of the move to acquire running-focused retail shops. "We want to be most aggressive, and it gives me the most confidence knowing I have strong partners who know the business, know the game, are highly motivated to grow rapidly."

Also Friday, Finish Line released fourth-quarter and fiscal year earnings that exceeded Wall Street expectations. But the firm's guidance proved unnerving to investors, who bid the shares down more than 13 percent in trading midday Friday.

For the quarter ended March 3, Finish Line reported earnings of $41.9 million, or 80 cents a share, compared with $34.3 million, or 63 cents per share, in the same period a year earlier.

The chain reported quarterly revenue of $456.3 million, an 18.6-percent jump from the same period last year. Same-store sales rose an impressive 10.8 percent, the 10th consecutive quarter the chain reported a gain in the key metric. Running shoes were strong performers again, along with Nike Elite socks. Online sales jumped 38.3 percent and now make up 11 percent of the chain's total.

But the company's first-quarter guidance gave investors pause. Finish Line said it expects earnings per share to drop about 30 percent below last year's 65 cents per share thanks to lower margins from an upcoming sale and planned investments to update the chain's in-store technology and add a social media operation.

Finish Line also plans to add 25 new stores this year and refresh dozens more, while closing between 10 and 20 underperforming locations. Between May and November, the chain plans to roll out new point-of-sale systems that include hand-held tablets in its 635 stores, Finish Line executives noted on the call with analysts.

The company expects to spend about $85 million for the capital expenditures, well above last year's $29 million total.

Lyon said investments in technology are essential for Finish Line to remain competitive and continue to build market share.

"Retail is changed forever," he noted. "We must align all of the different components of our business to deliver a consistent, seamless brand experience for our customers across all channels and in all touch points, brick-and-mortar stores, digital, mobile, social, e-mail and catalogues."

Investors were spooked, though. Finish Line shares fell more than 13 percent, to $21.99, in trading Friday.

For the fiscal year ended March 3, Finish Line had no interest-bearing debt and $307.5 million in cash and cash equivalents. In the fourth quarter, the company repurchased 300,000 of its shares for $5.9 million, and it still has 3.8 million shares remaining on a buyback plan to retire 5 million shares.