Aussie start-up Alta Group, which runs a mixed-martial-arts training app, has quietly gone public in the US listing on the NYSE American exchange, months after warning there was doubt it could continue as a going concern unless it raised further funds.

Alta Group Global, formerly known as Wimp 2 Warrior, raised $US6.5 million ($9.9 million) through its initial public offering priced at $US5 a share.