Under Armour (NYSE: UAA) shares tumbled 5.57% in pre-market trading on Friday following the release of its first-quarter earnings report. The sportswear giant's stock took a hit as the company's sales figures fell short of analyst expectations, overshadowing an improvement in earnings per share.

According to the earnings report, Under Armour posted quarterly earnings of $0.02 per share, doubling the $0.01 per share reported in the same period last year. However, the company's quarterly sales came in at $1.134 billion, missing the analyst consensus estimate of $1.154 billion by 1.77%. This represents a 4.22% decrease compared to sales of $1.184 billion in the same quarter of the previous year.

The disappointing sales figures highlight ongoing challenges for Under Armour in a competitive sportswear market. While the company has managed to improve its profitability, as evidenced by the increase in earnings per share, the decline in revenue suggests potential difficulties in maintaining market share or expanding its customer base. Investors will likely be watching closely to see how Under Armour plans to address these sales challenges in the coming quarters.