目前常用的地埋管有钢管、钢筋混凝土管、PVC硬塑料管，这些管道的成本都较高，且施工难度大。
At present, the common underground pipelines are steel tube, reinforced concrete pipe, and PVC hard plastic tube. The cost of them is much high and it is also difficult to lay out.
自由负重器械和机器负重器械都是受欢迎的力量训练工具，但它们不是唯一的选择，你可以用并不昂贵的阻力塑料管（译者：我猜是指用硬塑料管之类的代替拉力器啥的），或者甚至用自身体重进行力量训练（译者：俯卧撑嘛）。
Free weights and weight machines are popular strength training tools, but they're not the only options. You can do strength training with inexpensive resistance tubing or even your own body weight.
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