Discussion: Blocks.

Up to what distance do they use starting blocks? And what's the time/percentage gain of using them vs. not? (say, both at your level and Usain Bolts)

I don't know the answer to either question. I'm not using blocks tomorrow but only because I haven't had enough time to practice with them recently.

Blocks are used up to 800m, though only fairly serious runners would get much benefit at that distance. I seem to recall from my middle school coaching days that blocks were worth a couple tenths for kids in the 12-15 second range. I've obviously never worked with sub-10s sprinters but I am quite sure that's not even possible without blocks.

Noticed a few of the 400m runners at the state high school meet chose to use a standing start instead of the blocks. At that masters champs in Olathe (2 years ago?) noticed a lot of the older runners did not use blocks in the 200 (i.e, the 65+ age categories). At some point it's a trade-off between getting hurt versus a faster start.