As best as I can understand things, it seems that Nigg does not view impact
forces as being a problem. He generally cites a paper of his published in
1997 in which he reports the results of a graduate thesis (from a student of
his?) that showed that neither peak impact force nor vertical loading rate
are linked with higher injury risk. He reported that higher loading rate was
actually associated with reduced injury risk. I have not read the thesis to
which the paper refers, so I don’t know much about it – trying to get a
copy, but interlibrary loan has not come through yet after several weeks of
waiting. My problem is that if it is not published in a peer reviewed
journal, it is difficult to come to firm conclusions about the reliability
of the study. My understanding is that it also only looked at short term
injury risk and did not differentiate between types of injury.

Although impact force may be smaller than active force, impact loading rate
is generally higher, and loading rate is what others have suggested is
linked to injury. So basically, there is a debate in the literature as to
whether loading rate is linked to injury risk. Nigg would say no, whereas
others (like Jay Dicharry did in his post) would say yes.

Pete