Your feet stretch, flex, and spread when you move. When you wear athletic shoes with traditional lacing systems, your feet are not allowed to fully articulate. Non-elastic laces force to your feet to conform to the shape of your shoes. That seems silly.
iBungee and other manufacturers have produced life-changing technology! I only use elastic laces in my athletic shoes, and they are game-changers. My shoes flex and stretch with my feet to allow my feet to fully articulate as I move. All of my athletic shoes feel more like socks, and I experience very little foot fatigue even with very high training volume.
My current source for elastic laces with race locks is ForzaSports via their eBay store. I use the iBungee brand. I use them in all of my athletic shoes...including the shoes that I run obstacle course races in.
Now you know.