Arty,

This study is inconclusive. "While the concussed athletes showed a different response to breath holding than the control participants these differences were not significant between groups."

They fail to ask some of the obvious questions: Why is there a difference in blood flow and heart rate variability ?

Did you realize you double quoted the three paragraphs ? This may have been from the original source due to slight editing differences but it confuses the issue.

There is a lot of research done that appears to be without much purpose or useful result. The researchers are often like statistics gatherers with little input as to why the variation in the data sets. Graduate schools often require research projects with form (collecting data sets) more important than function (cause and effect).

This can cause anxiety where no anxiety is justified. In other words, a waste of precious brain energy.