Who speaking of head trauma , there is n't many fighters who have suffered more of it in the past 4 years than Jens Pulver .
Who has retired and unretired no less than 16 times in that span .
Speaking of head trauma , there are n't many fighters who have suffered more of it in the past 4 years than Jens Pulver , who has retired and unretired no less than 16 times in that span .