Give the BOSU, wobble board, and yoga ball a toss. They've got nothing on a slackline when it comes to preventing or healing sprained ankles and torn knees, according to a slackline study from the University of Salzburg, Austria.
For the study, researchers split 24 young adults into a control group and a slacklining group. The slackliners spent four weeks walking on a stretched piece of webbing. They walked a 30-foot line with help and, as their balance improved, were asked to do more challenging tasks on a longer line (up to 50 feet), including walking backwards, catching a ball, even juggling. Muscle reaction, movement, and strength measures, taken throughout the test on six lower body points, showed positive changes in joint stability and increased reaction time to a simulated slip. These results suggest "an injury preventative effect," says lead researcher Juergen Pfusterschmied. Benefits were most noticed in the knee, but the ankle and hip joint strength also improved.
"Standing on a slackline is a much greater challenge compared to other unstable training devices," Pfusterschmied says. "[It may] be useful for athletes to increase sports performance in general, but also for advanced therapy after ACL ruptures or ankle sprains." All you have to do is be able to actually stay on the line, a much harder task than it looks – try using ski poles when you start. And make sure to set the line up close to the ground, so you don't undo all the positives with a sprained ankle or twisted knee.