Tyler Cameron is living proof that no matter how in shape you might be ... a marathon can still kick your ass.
Gigi Hadid and Hannah Brown's ex-lover was among 50,000 people or so to run the New York City Marathon Sunday -- and probably among half who cramped up along the way. TMZ got this video of the model limping his way to one of the barricades in clear pain.
We're told this was shot about midway through the 26.2-mile trek throughout the city. Looks like Tyler's leg might've given out on him .