Acute effects on heart rate variability when exposed to hand transmitted vibration and noise.

OBJECTIVES: This study investigates possible acute effects on heart rate variability (HRV) when people are exposed to hand transmitted vibration and noise individually and simultaneously.
METHODS: Ten male and 10 female subjects were recruited by advertisement. Subjects completed a questionnaire concerning their work environment, general health, medication, hearing, and physical activity level. The test started with the subject resting for 15 min while sitting down. After resting, they were exposed to one of four exposure conditions: (1) only vibration; (2) only noise; (3) both noise and vibration; or (4) a control condition of exposure to the static load only. All four exposures lasted 15 min and the resting time between the exposures was 30 min. A continuous electrocardiogram (ECG) signal was recorded and the following HRV parameters were calculated: total spectral power (P(TOT)); the spectral power of the very low frequency component (P(VLF)); the low frequency component (P(LF)); the high frequency component (P(HF)); and the ratio LF/HF.
RESULTS: Exposure to only vibration resulted in a lower P(TOT) compared to static load, whereas exposure to only noise resulted in a higher P(TOT). The mean values of P(TOT), P(VLF), P(LF), and P(HF) were lowest during exposure to vibration and simultaneous exposure to vibration and noise.
CONCLUSIONS: Exposure to vibration and/or noise acutely affects HRV compared to standing without these exposures. Being exposed to vibration only and being exposed to noise only seem to generate opposite effects. Compared to no exposure, P(TOT) was reduced during vibration exposure and increased during noise exposure.