Heart rate variability: Response to graded head up tilt in healthy men

Abstract

At 70 degrees tilt, HRV measures, reflecting vagal contribution to cardiac-cycle length, decreased with reciprocal increase in sympathetic activity compared to 10 degrees or supine leading to increase in sympathetic predominance. A 10 degrees tilt, which is almost equivalent to lying down with pillow, did not change HRV from supine. activity.