In Olympic marketing, smaller brands find restrictions tough

Long in place, the Olympic Charter's Rule 40 limits athletes, coaches and other participants from appearing in advertising and other marketing, including social media posts, without the IOC's permission.

IOC spokesman Benjamin Seeley said in an emailed statement that about 1,000 brands applied and were approved.

Under Armour and Gatorade, for instance, came out with ads featuring swimmer Michael Phelps and tennis champ Serena Williams , among others, even though neither is an official Olympic sponsor.

"At first the waiver process did seem like a viable option, but when we started going down that path, we realized ... it's hard to do that in a generic, approvable way," said Jesse Williams, senior global sports marketing manager at Brooks Running, which sponsors eight Olympic athletes around the world, including U.S. runner Desiree Linden and decathlete Jeremy Taiwo.

To protest the rule, Brooks created a guerrilla marketing campaign — anonymously at first, until The Wall Street Journal identified the company by tracing internet-registration records.

Another athletic apparel brand, Oiselle, got in trouble after it congratulated a runner it sponsors, Kate Grace, on becoming an Olympian and going to Rio on an Instagram post after a qualifying event.