U.S. National Team alum and Central Florida linebacker Shaquem Griffin speaks with the media Saturday at the NFL Scouting Combine in Indianapolis (Photo by Adam Wire)

Shaquem Griffin's used to being doubted. He's dealt with it his whole life, let alone his football career.

Born without use of his left hand, Griffin had it amputated at age 4. Since then, he's been dominating on the football field, most recently at the University of Central Florida, where he helped the Knights go 13-0, was a two-time All-American Athletic Conference performer and the Peach Bowl MVP in UCF's 34-27 win over Auburn.

RELATED CONTENT: National Team alumni and identical twins Shaquill and Shaquem Griffin are making waves on their football teams

As the 2013 U.S. National Team alum entered this weekend's NFL Scouting Combine in Indianapolis, observers wondered how he would fare in the bench press without a left hand, or even if he would attempt it. 

Here's what happened.

Using a prosthetic on his left arm, @Shaquemgriffin just put up 20 reps on the bench press! 💪#NFLCombine @UCF_Football

📺: @nflnetwork pic.twitter.com/fHS0b4Eb0s

— NFL (@NFL) March 3, 2018

Impressive. But how did he do it, quite literally?

He used a prosthetic hand that attached to where his left arm ends. From there, Griffin explains it.

"Once I got (the prosthetic hand) fitted, there's a button I press, and it's like a suction cup," Griffin told the assembled media Saturday at the Combine. "I press the button, put it on, and it locks my hand, and then I have a clip that I put on the bar, lock it down and clip it."

RELATED CONTENT: U.S. National Team alumni audition for pro career at NFL Combine

Griffin said he'd never done more than 11 reps prior to Saturday at the standard 225-pound weight prospective draftees must lift at the Combine.

"I almost feel like I could curl 225 right now," Griffin said, referring to the adrenaline rush he's felt throughout the day. "Now it’s time for me to see if I can run fast (he's scheduled to do the 40-yard dash Sunday). I want to check off every single box about people saying what I can't do and what I can't accomplish."

NFL Network analyst Mike Mayock was as impressed with Griffin's bench press performance as anyone."I almost got choked up watching that today," Mayock said. "I couldn't believe he got the late invite here. He's really good on tape. This is a legitimate football player."

UPDATE: Sunday, Griffin again stole the show at the Combine, when he ran the 40-yard dash in 4.38 seconds, the fastest time for a linebacker since the Combine began keeping those records in 2003. 

WOW. WOW. WOW.

4.38u for @ShaquemGriffin!

The fastest 40 time for an LB since 2003.

📺: #NFLCombine LIVE on NFL Network pic.twitter.com/MkDdOHJ2XQ

— NFL Network (@nflnetwork) March 4, 2018

RELATED CONTENT: Watch these National Team alums at this weekend’s NFL Scouting Combine