Passage FiveOne of Dara Torres’ trainers is walking all over me. Literally. I’m lying on my stomach as Steve Sierra concentrates his entire 160 lb. on my glutei and hamstrings. It hurts, but in a good way. It’s all part of the flexibility--and strength-building regimen that Torres, who is making history, as the oldest swimmer to compete in the Olympics, credits with getting her 41-year-old body in good-enough shape to race athletes half her age. But resistance stretching, as it is called, is not just for the Olympians among us. Its focus on maximizing muscle flexibility has been useful for everyone from injured NBA players to children with cerebral palsy. The exercises may not look like much--they generally require no equipment other than a mat and maybe a towel and some straps--and they may not feel that strenuous, but you know the next day that you’ve had a workout. Resistance stretching centers on flexing your muscles even as you stretch them; for example, instead of simply releasing a leg lift, resist the urge to let your quad muscles relax on the way down. Unlike holding a muscle in a passively stretched position, the resistance route actively lengthens muscles through constant movement. "Resistance stretching goes deep into the joints and grabs more muscle fibers to increase strength and flexibility," says Tierney, Sierra’s partner. "It takes twice as much force to stretch a muscle as it does to contract it." I’m not convinced yet, but after they guide me through a few exercises my muscles do start to feel more energized I can see why Torres likes to be worked on half an hour before she swims. Although Tierney and Sierra have certified 250 trainers through weekend workshops, you might be hard-pressed to find a class at your local gym. That may have something to do with the fact that stretching has always been deemed the most disposable part of any exercise regimen. "People usually only think about flexibility and stretching when they are older and getting stiff or when they are injured," says Tiernjcy. "It’s just not considered sexy." That could change. As doctors urge even us non-Olympians to remain physically active throughout our lives, maybe we’ll start to pay more attention to stretching. After all, look what it does for Tortes. From the passage we know that Dara Torres is（）

A. a sports historian
B. a swimming coach
C. an Olympic champion
D. a professional athlete