For public health specialists this can be difficult ground.

对公共卫生专业人员而言，这可能是一个困难的方面。

youdao

I enjoyed playing in the centre of defence at such a difficult ground after playing at full-back in Brussels.

我在中后卫的位置上感觉很好，这要比在布鲁塞尔踢右后卫好多了。

youdao

This makes it more difficult for the body to effectively use the same amount of oxygen as it would on the ground.

VOA: special.2009.07.14

We slept on the hard ground, ate canned beans from cold metal plates and spent our days in the difficult search for gold.

VOA: special.2009.07.04

"There is a difficult situation on the ground in Pakistan.

VOA: standard.2009.03.11

Beyond the opponents, surprises always come up south of the border for the U.S. This day it was a field with grass as long as the first cut on a golf course, which made hitting crisp passes across the ground difficult.

WSJ: U.S. Soccer: Americans Hexed in Cup Qualifier

How far (if at all) there is now a rift between Salahuddin and the Pakistan-based leadership and Dar and his commanders on the ground is difficult to gauge.

CNN: From Our Correspondent: Peace Deferred

Given their inherent differences, in terms of both format and ideology, both plans are difficult to compare on level ground.

FORBES: Fiscal Cliff Should Help Obama And Paul Ryan Find Common Ground On Budget