Any research on the affect of starting blocks on sprint performance?

I think you're on the right track. But I don't think their usefullness is directly correlated with speed. I think it's more correlated with technique, with the caveat that someone who has good starting technique is much more likely to have a decent time/speed, simply because they're much more experienced.

For example, a young female runner may run 12 mids and that could be an absolutely fantastic time. The blocks could be extremely useful for them. They're just not that fast yet as they haven't developed.

Yep, you're almost spot on. I don't know if any research has been done, but I've timed a lot of short sprints (10m, 20m, 30m...) with high school kids using a few different timing systems (Freelap etc) and the only kids I've seen beat their standing start times from blocks were really fast boys, like sub 11.0 FAT for the 100m type boys. The really interesting tests were flying 10m runs with say 10m of acceleration from blocks or standing start, and the standing start almost always produces the faster time, meaning even after 10m of acceleration the standing start produces the faster time compared to starting from blocks. I've had some pretty fast boys and girls over the years and I'm skeptical that any women short of the elites benefit from blocks. This knowledge has changed the way I teach block starts now, for most kids I have them come up much higher in the set position so they don't have to dig themselves out of such a deep hole at the beginning of the race.

That’s interesting. Are you still having them start out of the blocks because block starts are required for the races?

I notice with youth athletes that I coach, we are always way ahead after 10-20m or so before being caught by faster runners out of blocks. Teams are putting 14s runners in blocks and it just makes no sense to me.

I dare you to go tell this to the coaches of female athletes at the Texas state meet. This is rubbish.

I don’t disagree, but where’s the cutoff? I’d love to see the data that reinforces who should, and should not, use blocks. As in “we tested 100 runners and not a single one was faster in blocks unless they were sub 24, regardless of technique or measures of strength”. That would be valuable coaching info.

I imagine the blocks feel pleased they are serving their purpose. I wonder what effect it has on them when they aren't being used.

Heres the thing. Are you not going to teach blocks til their fast? Professionals struggle with block starts being consistent at times. They need those reps from years of doing it. I do youth track in the summer and younger kids are basically the only group where I dont take the blocks out.

This is the right answer. You asked the question and I gave my experience but in the end I have yet to go to a high school meet and see anyone starting in the 100 or 200 from a standing start. So with long term development in mind you would be doing your youth athletes a disservice to not teach them to use blocks.

“Affect” matters. As they say, fake it till you make it.

Yes there is research and yes they help sprinters more than anybody else.