Shares of Under Armour Inc. /zigman2/quotes/208967132/composite UA +1.37% /zigman2/quotes/204420722/composite UAA +1.60% slumped 2.6% in premarket trading Friday, despite a rally in the broader stock market, as the athletic apparel and gear maker suffered collateral damage from rival Nike Inc.'s /zigman2/quotes/203439053/composite NKE +1.29% a disappointing earnings report. Also getting hit, yoga apparel and gear maker Lululemon Athletica Inc.'s stock /zigman2/quotes/204011506/composite LULU +1.09% slid 2.6% ahead of the open. Meanwhile, futures /zigman2/quotes/209948968/delayed ES00 -0.44% for the S&P 500 /zigman2/quotes/210599714/realtime SPX -0.12% rallied 0.5%. Nike's stock tumbled 10.2% in the premarket, after the company reported late Thursday fiscal first-quarter profit and sales that topped expectations, but warned that gross margins would be hurt for the rest of the fiscal year as it cuts prices to shed excess inventory. Among shares of other Nike rivals, Adidas AG /zigman2/quotes/206448829/delayed XE:ADS +0.32% /zigman2/quotes/203671926/composite ADDYY -0.35% dropped 5.1% and Puma SE /zigman2/quotes/203655455/delayed XE:PUM +0.08% /zigman2/quotes/210450025/composite PUMSY -3.06% sank 5.6% in Germany, while Asics Corp. /zigman2/quotes/207993898/delayed JP:7936 +1.33% /zigman2/quotes/203940894/composite ASCCY -0.78% slumped 10.7% in Japan.