Fitbit sales were almost three times as high in the quarter to 30 September 2015 than they were in the same period last year. Up from around $152.9m sales in the third quarter of 2014, the three months this year brought a $409.3m top line for Fitbit.

The San-Francisco based business showed investors its main product is still performing well, in a better than expected third quarter. The company's net income was down around 32% to $45.8m (£29.68m, €41.56m), mainly attributed to high operating expenses, which quadrupled in the three months. In its second results since Fitbit's IPO in June, Fitbit announced it more than doubled its sales volume, as health and activity tracking wearable technology proves to be increasingly popular.

"Revenue of $409 million increased 168% year-over-year, exceeding the high end of our guidance, and adjusted EBITDA nearly doubled," co-founder and chief executive James Park told investors. "Fitbit's third quarter results demonstrated the continued rapid growth of the Fitbit platform and our team's ability to execute on the tremendous opportunity we see globally, as we help people reach their health and fitness goals."

Fitbit says it is expecting a surge in sales in the last quarter, which will include Black Friday, Cyber Monday and Christmas, aiming at a $635m revenue. Full year sales are expected to be around $1.78bn.

Just hours after its floatation on 18 June, Fitbit shares soared by almost 50%, making it one of the most successful flotations of 2015 so far. It offered 36.6 million shares at $20 on the first day, raising a total of $732m. Shares had jumped to $29.68 by the day's close on the New York Stock Exchange.

The success of the flotation was especially impressive against the backdrop of Apple's recent launch of the Apple Watch, which contains many health-tracking capabilities.