Introduction
Protecting the body against the physiological consequences of stress is an important therapeutic goal. A generalised reduction in sympathetic nervous system influence upon cardiovascular activity has been demonstrated in previous studies on manual techniques aimed at the regulation of physiological processes. Harmonic rocking of the whole body has been found to produce significant physiological, developmental and behavioural changes in babies and children; this study aimed to examine what effects it may have upon adults, a highly under-researched population group in rocking studies. In this study, 12 male and 12 female participants were given a 5-minute harmonic body rocking treatment, and their cardiovascular responses to subsequent acute mental stress were measured and compared to control values.

Methods Subject acted as their own control, participating in a control condition (prone rest) and a harmonic body rocking condition. Heart rate, mean arterial pressure (MAP) and subcutaneous blood flow (SBF) in the plantar great toe pulp were measured to assess physiological reactions to a subsequent experimental stressor, the Stroop task. Measurements were taken during the stress task itself and during a 3-minute ‘recovery’ period that followed. Analysis of variance (ANOVA) with Tukey post hoc analysis and two-tailed paired T-tests were used in analysis of the data.

Results Where harmonic body rocking had been given prior to the stress task, there were: Significant reductions in heart rate compared to baseline (P<0.001) and control (P<0.0001) values Significant reductions in the extent of SBF and MAP changes in response to acute stress compared to control (P<0.001) A significantly higher SBF in the recovery stage compared to control (P<0.001) No significant changes in baseline SBF or MAP (P>0.05), heart rate reaction to acute stress (P>0.05) or ‘recovery’ of MAP following stress (P>0.05)

Conclusion The results of this study suggest that harmonic body rocking in adults may contribute towards the down-regulation of sympathetically-mediated cardiovascular responses to subsequent acute mental stress, as well as reducing resting heart rate. This regulation may be of therapeutic value to many patients, particularly those with cardiovascular pathology. Further research is needed to assess the full extent of neuro-hormonal effects mediated by HBR, as this study only examined cardiovascular parameters, as well as the duration and mechanisms of these effects.