Fitbit, the company known for wearable devices promoting healthy lifestyles, saw its shares surge Thursday following the biggest stock offering this year for the tech sector.

Shares in Fitbit vaulted up 51 percent in early trade to $30.26, after the initial public offering at $20 a share raised up to $732 million.

The market value for Fitbit was some $4 billion based on the IPO.

Fitbit was a pioneer of "wearable computing," where it faces longtime rivals such as Jawbone and new competition from Apple Watch and Android-powered smartwatches.

Fitbit said it has sold more than 20.8 million of its clip-on or wrist-worn devices, and claimed to have a leading position in the US fitness-focused activity tracker market last year.

Like other fitness trackers, wearable devices equipped with sensors feed information to smartphone applications that tap into the analytic power of computers in online data centers.

Fitbit had a profit of $131.8 million last year and just shy of $48 million in the first quarter of this year, according to documents filed for its IPO.