There is no published research that objectively
assesses the physiological changes involved with the reported
relaxation response following TTM, which could be done
using methods such as evaluation of heart rate variability.
Heart rate variability (HRV) is controlled by the autonomic
nervous system. Generally, sympathetic nervous
system (SNS) activity increases heart rate (decreases HRV)
and parasympathetic nervous system (PNS) activity
decreases heart rate (increases HRV). Observed HRV is
believed to be an indicator of the dynamic interaction and
balance between the SNS and the PNS (Terathongkum and
Pickler, 2004; Task Force of The European Society of
Cardiology and The North American Society of Pacing and
Electrophysiology, 1996).