While the fraction of total tau protein was shown to have increased in control athletes and athletes after concussion and TBI in several studies,25,26 we provide direct evidence that tau protein levels increased in the blood as a consequence of physical training, which is consistent with our previous observations.27 However, the significant increase in the level of p-tau181 relative to total tau in the plasma after regular physical soccer training and nonconcussive repetitive heading of the ball was unexpected, and to our knowledge is being reported for the first time. The gene discussed is MAPT; the disease is brain injury.