Sean Penn Shirtless With A Six Pack [PHOTOS]

There are certain things you need to do if you have a 26-year-old girlfriend and want to keep her. One of those things is getting in shape.

It looks like Sean Penn was doing just that. He’s got the start of a six pack going on there. the actor went for a jog yesterday (August 29), and was closely followed by 26-year-old Shannon Costello, who looked svelte in tight lycra leggings.

PHOTOS: A Shirtless Sean Penn Shows Off His Ripped Bod And New Lady

She and Penn first met in the autumn of 2009 and the pair became friends, with Costello starting work with J/P Haitian Relief Organization back in 2010. The couple began dating in July shortly after Penn’s split from Scarlett Johansson.

48 PHOTOS OF Sean Penn & Scarlett Johansson Attend Washington Correspondants Dinner

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