The effect of a single continuous IV on within subjects change

Could someone please suggest the most appropriate method of analysis to examine the effect of a continuous IV on a within subject (repeated measures) DV with 2 levels (pre-post)?

I have a leadership intervention where we measured "leadership style" (DV) before the program and again after the intervention. I want to know whether characteristics of the leader had an effect on the amount of change from pre-to post. Do certain leaders benefit more from the intervention? e.g Do we see improved outcomes amongst leaders who are more experienced, more motivated at work, or are male etc?

For IV that are nominal (e.g gender) I used 2-way mixed ANOVAs whereby the sample was split into two between subjects factors

Male Pre Post
Female Pre Post

I'm not sure how to analyse the effect for IV that are continuous- such as age, years of experience, motivation etc. I initially did a median split and continued to use the 2way mixed ANOVA but feel that there is probably a more appropriate way to do it.

Please help.