Run, Sébastien, run!  During his Major League Soccer career, Sébastien Le Toux built his reputation on relentless endurance, routinely covering more ground than younger teammates and opponents. “I was not strong, I’m pretty skinny, and I don’t really like physical contact, but running was something that I could do for an entire game,” the former Philadelphia Union player, 42, told The Post. “By the end, everyone was tired, but I was still able to run .”  Sébastien Le Toux is a French retired professional soccer player. Icon Sportswire via Getty Images That stamina wasn’t forged solely on the pitch. Instead, Le Toux credits an unlikely training ground for his edge on the field — the pool. “I’m not a good swimmer, but swim apnea is a great tool to develop your aerobic [capacity],” said the Frenchman, who retired from professional soccer in 2018. Also known as dynamic apnea training, the unique exercise is widely used by freedivers to improve breath control and underwater endurance.…