wysiłek umysłowy

It was several minutes before he felt able to renew the mental effort.

She suddenly had to put all her mental effort into not throwing up.

I am unable to write and any mental effort makes me feel sick.

It was hard to figure, and not important enough to warrant the necessary mental effort.

He cut the words with a mental effort and turned to stare down at the engine.

It was simple and required no mental effort from me.

Every mental effort was, however, succeeded by great physical fatigue.

The girl was well, just tired after her great mental and emotional effort.

But he could afford little mental effort to worry about that now.

There was sweat on his forehead from the mental and physical effort.