After 48-percent jump in debut, shares of Fitbit continue charging for a second day

Fitbit is sprinting for a second consecutive day, with shares of the fitness tracking device maker jumping 7 percent Friday after its strong debut as a public company.

The San Francisco company is the biggest seller of wearable fitness trackers, a new but fast-growing business.

Fitbit was founded in 2007 and started selling its products in 2009. It sold 10.9 million devices last year, eclipsing the combined sales from all previous years combined. Its revenue spiked by $474 million in just one year, to $745 million in 2015.

Fitbit's initial public offering raised $731.5 million. That made it the fourth-largest IPO in the U.S. this year, according to IPO ETF manager Renaissance Capital.

Investors have been hungry for IPOs this year and they're going to get a feast next week with 12 planned. Those companies could raise a combined $2 billion. Even energy companies, which are getting pummeled by low prices, are getting in on the action. There are three planning to list next week.

Wall Street responded enthusiastically to Fitbit's public debut. After saying it May that it expected to raise as much as $100 million with its IPO, it raised that projection twice.

The final $20 pricing Wednesday night was above even the company's most recent projections.

Fitbit Inc. stock jumped almost 50 percent Thursday and advanced $2.12 to $31.80 in afternoon trading Friday.