This was last weekend, at the ITU WTS Triathlon in San Diego. These guys are running very fast. The reason? They don't let their feet spend much time on the ground. Even Huerta, who looks like he's about to heel-strike, isn't actually, as he quickly moves the foot more under his hips, from a supinated landing to toe-off.
Want to get faster at running? Perfect the foot-strike. Go on runs where all you do is pay attention to your foot-strike. When the heel contacts first, the foot can not get off the ground until the forefoot lands, and then it can toe-off. That takes time, a lot of time when you add it up over hundreds/thousands of foot-steps. If the forefoot to mid-foot lands first, that will reduce the time, so the athlete can spend more time propelling themselves. More propelling means faster.
Focus on perfecting your foot-strike to be more mid-foot to forefoot, and you'll be faster.