Rob Kardashian Posts Exercise Motivation Photo

09/04/2013 09:26 am ET

Rob Kardashian took to Instagram Wednesday morning to post what he calls a "motivation time" picture.

Kardashian stepped out in May to debut his Arthur George sock line, and also his major weight loss. He credited his initial weight loss with a strict diet and two-a-day workouts.

On "Keeping Up With the Kardashians" last season, he said that he gained nearly 40 pounds while dating Rita Ora.

He also revealed his "little problem" as a result of weight gain: his supposedly shrinking penis. The upside? "Every time you lose 10 pounds you gain an inch on your penis."

Here's hoping some things are shrinking while others are growing.

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