Patients were rendered instantly unconscious by the electrical current

English as a Second Language English Vocabulary, Grammar and Idioms
1

Patients were rendered instantly unconscious by the electrical current, but the strength of the muscle contractions from induced, uncontrolled motor seizures often led to compression fractures of the spine or damage to the teeth.

  1. I can’t workout the bold part. Could someone please explain it to me?

A unified mechanism of action has not yet been established and remains the subject of numerous investigations.

  1. What is the subject of the “remains”?
2

  1. The electrical jolt causes the muscles to contract, The muscular contraction was severe, and as a consequence, the body tried to tear itself apart.
    Strength is modified by of muscular contractions.
    It’s also modified by from uncontrolled motor seizures

  2. The mechanism pf action remains the subject of investigations.

3

Thanks, Mr. Steve Thomas for your kind response.

I still don’t understand the function of “but”. What is the role of “but” here?

4

One more question:

The following sentence follows …

Patients were rendered instantly unconscious by the electrical current, but the strength of the muscle contractions from induced, uncontrolled motor seizures often led to compression fractures of the spine or damage to the teeth. In addition to the effect this physical trauma had on public sentiment, graphic examples of abuse were documented in nonfiction.

Does “the effect” refer the effect mentioned in previous sentence?

5

The brain controls “voluntary” muscles. If you go unconscious, you normally will go limp. These victims did not. The “but” is there because the tightening of the muscles is unexpected.

“The effect” refers to changes in public sentiment. The prior sentence addressed cause, not effect.