Watch Harper's eye-popping squat workout

PHILADELPHIA -- Consider this fair warning to all National League pitchers: Phillies slugger Bryce Harper is using the extra downtime to bulk up even more.

The 2015 NL MVP posted Instagram photos and a video of himself lifting a substantial amount of weight while doing a front squat, with the caption:

"I rather be lifting one into the second deck for a '3' run shot, but this will have to do for now. Philadelphia I miss you!"

Harper hit 35 homers in his debut season with the Phillies last year, while also racking up a career-high 114 RBIs. For the record, seven of No. 3's 35 homers last year were "three-run shots."