Compression technology is a hotly debated topic. On the one side, supporters claim it will increase the efficiency of your muscles' circulation, improving performance and your recovery rates in the process. Sceptics argue that the science doesn't stack up and you're essentially just wearing tights for no reason. We're a forward-thinking bunch here at TR HQ, so we've rounded up the best compression leggings for trail running we could find and assessed their effectiveness. Conclusion: they are really, really tight.