Task: Answer Verification
Input (English): Question: Is low-frequency spectral power of heart rate variability a specific marker of cardiac sympathetic modulation?
Answer: Although preganglionic cardiac sympathetic blockade reduced the LF/HF ratio during tilt, it did not alter spectral power in the LF band during rest or tilt. Accordingly, low-frequency spectral power is unlikely to specifically reflect cardiac sympathetic modulation in humans.
Output (English): no