Robert Goodman wroteWhose momentum: the defender's or the kicker's? If the contact is caused in part by the kicker's own motion, no foul in Fed.
NFHS 9-4-5 is VERY specific "A defensive player SHALL NEITHER" run into nor rough a kicker, which places the responsibility on the defensive player to avoid contact. The rule further provides 4 general categories of exceptions to that responsibility:
a. Contact is UNAVOIDABLE because it is not reasonably certain that a kick will be made.
b. The defense touches the kick near the kicker and contact is UNAVOIDABLE
c. Contact is slight and is partially caused by the movement of the kicker.
d. Contact is caused by R being blocked into the kicker or holder by K.
The defense is forewarned and will be held responsible for contact with the kicker (exceptions included) and will suffer the consequences of doing so. The judgment of whether, OR NOT, any contact with the kicker is excused by the rule exceptions rests EXCLUSIVELY with the covering official on EACH INDIVIDUAL kicking situation. There is NO "One size fits all" application