The cumulative effect of sub-concussive impacts has a serious impact on the brain's ability to tolerate further impacts.

The skeet shooting would have the greatest impact on the brain since the repeated shock waves from the shooting, both the sound shock waves and the recoil have a possibility to effect the brain.

Another way the brain can be compromised is by high fever or high intoxication. Strong hits to the body in sports can also contribute.

But, trying to assign rhyme or reason to PCS symptoms is difficult.