Nike Inc and performance apparel firm Under Armour are continuing to gain massive traction in the rapidly growing, high margin activewear segment - but at the expense of Adidas and smaller brands, according to a new survey.

The 'Activewear Survey-Dominant Players Gain Ground in Shopper Preference' report by the Cowen Group revealed Nike's share of first choice preference in activewear increased to 42% in January from 38% a year earlier. Under Armour's share increased to 13% from 11% in January 2013, both for the total popluation.

Adidas, however, lost some ground while Reebok remained "stable", likely reflecting some benefit from the brand's affiliation with CrossFit, the report noted.

Amongst males, Nike share increased to 44% from 38%, with preference for the brand even stronger for younger consumers, especially men aged 18-34 where share increased to 56% from 47% in January a year earlier.

"This metric strikes us as extremely important as members of this cohort are likely among the most important purchasers of athletic apparel," report authors noted.

Under Armour has been gaining momentum among women, with its share of preference in this category increasing to 12% from 10%. Among women aged 18-34, preference increased dramatically year-on-year to 13% from 9% a year earlier. And this, considering the firm has not yet unveiled its new women's strategy.

Both Under Armour and Nike's strength, however, appears to be coming at the expense of major rival Adidas, Hanes and smaller brands including Faded Glory and Athleta, which all experienced erosion in preference in January.

The report showed preference for C9 by Champion remained "stable", which it said was "something of a victory in light of TGT's ongoing negative traffic trends", while Athleta appeared to have "very limited" traction.

Digging deeper, the number of respondents who chose beleaguered Canadian yoga wear brand Lululemon Athletica as their favorite athletic apparel brand was so small it raises "issues of statistical significance", the report noted.

Indeed, in January 2014, of the 2,500 respondents, only 14 women and three men chose Lululemon as their favorite athletic apparel brand.

"Lululemon spiked as a first choice brand last July, and has come in to fairly stable levels since then. [The report] indicates that both the spike and then decline to a plateau are more pronounced among the key constituency of women ages 18-34," the report stated.

Lululemon has been embroiled in complaints over the quality of its products for nearly a year, and in January lowered its fourth-quarter earnings and sales guidance due to declining traffic and revenue trends.