interesting question, given I need to look this up as someone I know has neural tension.  Not that my knowledge would be up to date now, but given my original training was physio, neural tension use to be based upon symptoms experienced at various degrees of slump, knee extension plus adding in neck flexion.  Ask your local physio department at the university you are at, they should know about normal values, I am not sure

Dear Deborah,

Thanks, I already asked several but there is very little information. It would be interesting though to compare values and to measure change.

Hope these might be of your interest

http://libres.uncg.edu/ir/uncg/f/d_perrin_comparisonofnonballistic_1997.pdf

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2565640/

Dear Vasanth Kumar,

Thank you very much. Interesting material I have to say!