Jason Kelce's competitiveness hasn't lost a step in retirement ... 'cause the future Hall of Famer challenged several Navy SEALs to a push-up contest on Veteran's Day!!
The big showdown happened during "Monday Night Countdown" at SoFi Stadium in Los Angeles ... with the action starting well before the Rams and Dolphins kicked off their primetime matchup.
Kelce rocked a tight tank top for the contest ... and he explained he knew he was in for a tough task ahead -- but that didn't prevent him from going through with it.