Unit 108：Get into the swim第108单元：游泳去One of the best all-around exercises,swimming increases both cardiovascular and muscle strength.游泳能促进心血管及肌肉的耐力，是最佳的全身运动之一。There is hardly any stress on your body's joints,because water turns you into a kind of weightless underwater astronaut,游泳时你全身的关节几乎没有任何的压力，因为水使你变得好像是一个处于无重力状态的水底航天员，making your every movement an easy,flowing one.使你的每个动作轻松又流畅。But water also offers resistance that helps you build muscle strength and tone.但水提供的阻力也会帮助你强化肌肉使其结实有力。Doing laps in a pool-no matter what the stroke-is excellent exercise.不管你用什么姿势游泳，在泳池里来来回回的游都是绝佳的运动。You can also "take a walk"underwater or perform calisthennics like leg lifts or arm circles.你也可以在水底“散步”或做抬腿或转手臂的体操。Research shows that water actually offers an equal aerobic workout in less time than one on dry land.研究显示，在水里做有氧运动能以较少时间达到在陆上做的同称效果。A half-hour of walking in water equals the energy output of a two-hour walk in the woods,one study showed.某研究显示，在水里走上半小时和在树林里走上两小时所消耗的能量相同。Make sure you're about chest deep(to benefit from the resistance)and simply go for a stroll.确定水深要及胸(这是为了从水的阻力中获得对身体的好处)然后就开始水中散步吧。