Shares of Fitbit opened 52 percent above their IPO price on Thursday, putting it on track to rank among the top 10 stock market debuts of the year.
The stock opened on the New York Stock Exchange at $30.40.
(See what shares are doing now.)
More than 40 million shares of Fitbit had traded by early afternoon EDT, with shares at $29.93. For comparison, data storage firm Box traded 42.6 million shares in its first full day of trading on Jan. 23.
The fitness wearables maker had priced its initial public offering at $20 a share on Wednesday, a day after it raised its IPO price range to $17 to $19.
The company is currently valued at $4.1 billion, and many investors will be eyeing its IPO since it is actually profitable.
Read More How to lose 30 pounds and earn $120M on Fitbit
Still, Fitbit is competing in an increasingly crowded market, with rivals like Apple, Garmin and Jawbone competing for a piece of the lucrative space.
Fitbit CEO James Park told CNBC's "Squawk on the Street" ahead of the IPO that he believes his company can stay competitive even as Apple and other electronics makers ramp up marketing for all-purpose wearables like the Apple Watch.
"There's over $200 billion of consumer spending on health and fitness. This is a massive market. There's room for more than one dominant player," he said. "The brand Fitbit is really synonymous with health and fitness tracking, so we feel that we have really significant competitive differentiators in the market."
Park said Fitbit controls 85 percent of the wearable fitness tracking market, and the brand name is more widely searched on Google than Under Armour, Lululemon, Adidas and Garmin.
Investors should not be overly concerned that Fitbit will lose its first mover advantage in the next two years, said JMP Securities analyst Alex Gauna, noting that the Apple Watch had not "come out of the gates blazing."
"Apple is not in this market with comparable performance in terms of either price point, or integrated GPS, or battery life, so there's a lot of room for Fitbit to maneuver within the next couple of years," he said Thursday on CNBC's "Squawk on the Street."
Read More Fibit's future: Can it compete with Apple and Google?
Beyond the medium-term, Gauna said Fitbit faces significant challenges competing with the power that Apple can bring to bear in the battle over the Internet of Things, the emergent space for connected devices.
Fitbit is well-positioned because it integrates with both Apple's iOS and Google's Android mobile operating systems, but it must continue to innovate beyond its fairly narrow product range, Gauna added.
Read More Apple mines big profits from Watch band
Park said Fitbit cannot comment on details of its product pipeline, but he noted that research and development investment has doubled year over year, and the company will triple that spending to more than $150 million.
Fitbit has expanded into scales and electronics products that can be clipped to apparel. Park said services hold much potential.
"I think the next step is software, which really makes sense of the data to give you insights, coaching and guidance," Park said.
Jonathan Roosevelt, chairman of Roosevelt Capital and an early investor in Fitbit, told "Squawk Alley" he thinks of Fitbit not just as a health care company, but as a hardware and software firm in the mold of Apple.
Roosevelt conceded that Fitbit could indeed be disrupted, but he called Park "the best strategic mind I've ever met in technology."
"I'm confident he'll stay in front and continue to innovate and release new products," he said.
Fitbit has been held up as one of the rare tech companies to be profitable at the time of its IPO. In the first quarter of 2015, Fitbit generated net income of $48 million, a more than fivefold increase from a year earlier.
Read MoreTech profit? FitBit shows it's possible
However, the company's marketing costs are also rising. The company spent $112 million on marketing in fiscal year 2014, up from $27 million in the prior year.
"What Fitbit recognizes is that they have to continue to establish brand leadership, and they see marketing as an opportunity to stay in front," Roosevelt said.
Worldwide shipments of wearable devices are set to jump 173 percent to 72.1 million units this year, according to global markets intelligence firm IDC. By 2019, IDC forecasts shipments will grow to 155 million units.
As the segment expands, there is still plenty of room for players in the wearables space to pick up market share, said Ramon Llamas, IDC research manager for wearable and mobile phones.
"If you're Fitbit, your core competency and your goal is to evangelize health and fitness activity ... so it's very much a very core set of value propositions right there," he told "Squawk Alley." "Whereas if you're an Apple or an Android Wear or a Microsoft, you're looking to be a device for all people."
—CNBC's Kayla Tausche and Ari Levy contributed to this report.