My DD has been triggering a vagus nerve response while doing some of her tumbling passes and vault. It is especially bad punching out of front layouts. She says it is really scary because she starts to feel like its hard to breathe then her heart starts beating hard and her throat gets tight. Her doctor originally thought it was exercise induced asthma, but an inhailer didn't help. He now thinks it is the vagus nerve response to her holding her breath and keeping her core tight. I have read somewhere that this is common in upper level gymnastics. Have any of you had experience with this?