Sportswear brand Under Armour is being sued by footwear brand Gravity Defyer over its use of the G Defy name on its footwear.

Gravity Defyer is challenging Under Armour's use of the G Defy name being used for "speciality shoes with soles of thin, lightweight, full-length, Micro G foam that turns cushioned landings into explosive takeoffs".

The lawsuit, filed in the Central District of California, accuses Under Armour of inappropriately trading on Gravity Defyer's trademark to draw attention to its product.

Meanwhile, in February, Under Armour filed a lawsuit claiming that Nike was infringing its I Will trademark.

The lawsuit, which was filed in the district court of Maryland in Baltimore, said Nike launched an advertising campaign for its performance apparel, footwear, accessories and sporting goods last year, which repeatedly uses the phrase "I Will". 

Yet Under Armour claims Nike's use of the phrase imitates its "I Will" trademark, which is used for the same types of products.