"Got it in with @gunnarfitness," Kardashian captioned the pic.
It seems the new dad has been on a health kick lately, sharing a pic of his new diet earlier in the day.
"Green juice time ?????☘️☘️?? woohoo.... and this weather is perfect ??? greeeeeeen (kale, spinach, romaine, parsley, cucumber, celery, apple, lemon, ginger) movieeeee," he wrote alongside a shot of his green juice.
While Kardashian looks to be getting in shape, it won't be for the cameras. A source revealed to ET on Wednesday that the sock designer and his former fiancee, Blac Chyna, had called it quits again, and therefore would not be filming a second season of their E! reality show, Rob & Chyna.