If you use the CS port over the High Power Port, the current is limited which will reduce the frequencies ability to resonate your muscles/nerves. The only thing lost is high frequency harmonics which won't be very high if you are in the range one can feel frequencies.
You will only feel it if it is resonant, and this only happens below 10,000 Hz.
You can avoid this sensation by running higher frequencies, or use the CS port without worry.
If you lower the amplitude, you run the risk of lowering to the point where it will not penetrate the body and thus reduce efficacy.
For more details, please check the link: