National Geographic

Paralympic visuallyimpaired skier DanelleUmstead, 46, tests heraerodynamics in a windtunnel to learn bettertechniques for draftingbehind her sightguide (not shown),who skis in front ofher. Paralympic skierscan reach speeds of70 miles an hour.MARK THIESSENPREVIOUS PHOTOParalympian sprinterJarryd Wallace’s bio-mechanics are analyzedat the SouthernMethodist UniversityLocomotor PerformanceLaboratory in Dallas,Texas. “There was a lotI was doing wrong,”says Wallace, 28. Thefour-time world recordholder, whose lowerright leg had to beamputated becauseof a muscle disorder,uses the lab’s analysisof his stride to runeven faster.ROBERT CLARK58