Hi Viktoria! I'm sorry; we dropped the ball on emailing all the applicants who had previously submitted. In hindsight, this was an obvious first thing to do. We did post the extension on the EA Forum and LessWrong posts, and a host of Slack workplaces and Facebook groups, but we should also have sent that email.
Application deadlines have been extended to May 22! Feel free message me or Victor if you have any questions.
I wrote a short blog post a little while ago on preventing low back pain with exercise. I think your problem area report might have missed several important meta-analyses on low back pain. In particular, Huang et al., 2018 and Shiri, Coggon and Hassani, 2017 seem to supersede Steffens et al., 2017, and Lin et al., 2018 seems broader and more recent than NICE, 2016. I think your assessment of the quality of evidence in favour of exercise interventions for low back pain might reasonably update with respect to these references.
Open again for 20k people at $50 each.
Regarding Magnus' post, which you linked, I partly wrote this article as a response. The evidence base for preventing low back pain with exercise seems much greater than that for adjusting posture, stretching and using ergonomic furniture, which his post also recommends. I wanted to emphasise the importance of exercise as the primary intervention.
Regarding global health, the Happier Lives Institute produced a report on pain in 2020 that identified low back pain as a focus area, but missed my references [3-5]. In particular, my reference  seems to supersede their reference (Steffens et al., 2017) and my reference  seems broader and more recent than their reference (NICE, 2016). I think their recommendations might reasonably update with respect to these references.