You may already be doing this, so my comments may not help at all (sorry if so)
First, I would suggest upping the amount of alternative types of photography you do, particularly around the time of running events, maybe even try some sort of photography genre you do not find appealing at first glance.
I have lately come across a couple of YouTube posters who film themselves going out and doing landscape photography. I am not a particular fan of landscape photography, for example I would never buy a calendar of landscape views. However being a bit bored I thought why not go out and try it for an afternoon, nothing to loose. So off I went. It was actually (for me, maybe not for others) hard to get well framed / composed images. In fact I have gone out a few times now (local micro views not mountains) just because I find it more challenging than I expected and trying to improve is interesting and challenging - even though I do not love this area of photography for itself. I will never be a committed 'Landscape Photographer' as frankly I dont care enough, but I am enjoying doing something different and it is challenging my skill set and improving it, and I can apply some of that learning to other areas of photography.
Other possible challenges worth a try are macro photography, photographing anything as if you are trying to sell it etc. There does not have to be personal appeal in a subject, just something very different to your usual or something that needs a different skill set. Then do your photography/post processing mixed in with the time you spend doing the running stuff, so that you can add in variety.
The other thing I would do is sit somewhere nice (garden, pub) and make a playful list of stuff, something like
Higher, lower, diagonal, curving, light against dark, abstract, crowd, small detail, fast shutter, slow shutter, feet etc
Then in moments when not doing your standard running shots, try to get in ones that incorporate stuff from your playful list.