Originally massage guns were pitched as pieces of fitness equipment which can alleviate tight, sore and aching muscles after a hard workout. They do this by jackhammering your target areas with vibration therapy or, increasingly, percussive therapy (both of which will be explained below). In essence, a massage gun is a handheld and sometimes deeper reaching version of a foam roller or a sports massage therapist and aims to relieve stiffness and soreness brought on by athletes' and fitness fanatics' training. The Theragun by the recently rebranded Therabody is one of the most popular on the market and has developed a celebrity following. According to a recent press release, Rihanna, Jay-Z, Justin Timberlake, Marcus Rashford, Kevin Hart and Shawn Mendes have recently invested in the company, and everyone from Kate Hudson to Shakira to Dwayne Johnson is a confirmed fan.