extra heavy

基本解释

You may have noticed that you feel extra heavy, lethargic, that you feel gravity’s pull is greater.
你可能已经觉察到那时候的你感到非常沉重，昏昏欲睡，感觉地心引力都变得更大。
Along this line 20,000-ton coal trains can reach a length of over 7 km pulled by powerful electric locomotives over an extra heavy duty track and driving down operating costs.
大秦线上运行的两万吨运煤列车长度可达7公里，由大功率电力机车牵引，大大降低了运营成本。
Though I lost weight by doing body building, I used to do three out of four sets with light weights, the fourth set was extra heavy just to make me feel good (see point below).
虽然我是通过健身法来减肥的，但我曾做四组力量训练，前三组的重量轻，第四组要重——这只不过是让自己感觉帮一些罢了（见下一条）。

Discounts for big users are tiny because of the heavy extra costs imposed by the government to subsidise renewable energy sources (due to provide 20% of capacity by 2020) and to reduce the life of nuclear power plants to 32 years (from 50 years).
ECONOMIST: German business