Two American athletes who recently staged protests on the medal stand at the Pan American Games were given 12 months of probation, with the head of the U.S. Olympic and Paralympic Committee warning of harsher punishments in the future to any athletes who might stage similar demonstrations.

“It is also important for me to point out that, going forward, issuing a reprimand to other athletes in a similar instance is insufficient,” USOPC CEO Sarah Hirshland wrote to fencer Race Imboden and hammer thrower Gwen Berry in letters sent Tuesday, copies of which were obtained by The Associated Press.

Imboden took a knee on the podium in Lima, Peru, after helping the U.S. men’s foil team win gold. Following her individual win Berry raised a fist and bowed her head as a rendition of “The Star-Spangled Banner” neared its close.

To compete at the Pan Am Games, athletes had to agree to rules forbidding political demonstrations, and the International Olympic Committee has similar ones in place. Imboden and Berry will be allowed to potentially compete at the 2020 Olympics in Tokyo, but Hirshland signaled in her letter that she wants to head off athlete protests on what would be a vastly bigger stage.

In a Twitter post the day of his protest, Imboden said that while he was “honored to represent Team USA at the Pan Am Games,” he felt compelled to present a “call for change.”

“My pride ... has been cut short by the multiple shortcomings of the country I hold so dear to my heart,” the 26-year-old wrote. Among the issues Imboden said he was protesting: “Racism, Gun Control, mistreatment of immigrants, and a president who spreads hate.”

Berry, 30, said her raised fist was “just a testament to everything I’ve been through in the past year, and everything the country has been through this past year.”

“A lot of things need to be done and said and changed. I’m not trying to start a political war, or act like I’m Miss Know-it-all or anything like that,” she added. “I just know America can do better.”