The body has an internal program that automatically evaluates and responds to the conditions it is working in, but it doesn’t have any way to know on its own what sort of oxygen load it is going to need in the future. It responds to the workload of the moment. When a sudden spike in heavy exertion happens, the body has to play catch-up. When you don’t plan for breathing in a workout, it’s easy to end up with an oxygen deficit.
