In nearly a decade of competitive freediving, 34-year-old set 11 South African records, including a dive in the Red Sea to 207 feet on one breath. She did it through mental training and a strict regimen of chest stretches that increased her lung capacity from four to six liters. Now she鈥檚 teaching her hard-earned lessons to athletes from a range of backgrounds, from big-wave surfers like Greg Long鈥攚ho need to endure crushing hold-downs after wiping out鈥攖o rugby players and cyclists looking to gain a competitive aerobic edge. Ultramarathoner Ryan Sandes credits Prinsloo鈥檚 training with helping his body use oxygen more efficiently. 鈥淓ven if it makes me only 2 percent better,鈥 Sandes says, 鈥渋t鈥檚 worth it.鈥
In her courses, Prinsloo focuses on yoga-like poses and breathing techniques (See the sidebar). The results, she says, are as effective as any performance-enhancement procedure. 鈥淵ou don鈥檛 have to inject a cup of your own blood,鈥 she says. 鈥淭here are other, legal reserves you can tap into.鈥