Summary:
Interest in improving the body’s response to stress has increased the amount of research into how the autonomic nervous system is affected by mind-body practices such as yoga, Tai Chi and Qigong. These practices are known to increase activity in the parasympathetic nervous system, which helps the body recover from stress. They also appear to improve cognitive function, although the biological mechanisms responsible for these benefits are not fully understood. Two common features of these practices are paced breathing and rhythmic muscle contractions. Paced breathing is thought to increase parasympathetic activity by synchronising breathing with heart rate, with the greatest effect occurring at a breathing rate of around six breaths per minute. Previous research has also shown that rhythmically contracting and relaxing large muscle groups may independently produce similar effects. This pilot randomised experimental study investigated the individual and combined effects of paced breathing and rhythmic muscle contractions on parasympathetic nervous system activity during a cognitive stress task. Male participants were randomly allocated to one of four groups: paced breathing, rhythmic muscle contractions, paced breathing combined with muscle contractions, or a control group. Heart rate variability was used to measure autonomic nervous system activity. This study found that rhythmic muscle contractions produced greater parasympathetic activation than paced breathing alone. The combination of paced breathing and rhythmic muscle contractions resulted in the strongest response, producing significantly greater parasympathetic activity than the control group and muscle contractions alone during the stress task. These findings suggest that combining paced breathing with rhythmic muscle contractions may improve the body’s ability to recover from stress and may help explain some of the stress-reducing effects of mind-body practices.
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Abstract:
Mind–body disciplines such as yoga, Tai Chi, and Qigong have been demonstrated to activate the parasympathetic nervous system, but it remains unclear how these practices achieve these results, whether by breathing, movement, or some combination. This pilot study establishes a model to examine the individual and combined effects of paced breathing and rhythmic skeletal muscle contraction on the activation of the parasympathetic system during a cognitive stressor. Male participants were randomly assigned to one of four preconditioning groups: (a) paced breathing alone, (b) alternating upper extremity muscle contractions, (c) paced breathing synchronized with alternating contractions, or (d) a neutral control task. Autonomic response was assessed by heart rate variability during a standardized cognitive stressor. The alternating contraction group had 71.7% higher activation of parasympathetic signal over respiration alone (p < .001). Alternating contractions synchronized with breathing demonstrated 150% higher parasympathetic activation than control (p < .0001). Comparing the contraction alone and synchronized groups, the synchronized group demonstrated 45.9% higher parasympathetic response during a cognitive stressor (p < .001). In conclusion, paced breathing synchronized with rhythmic muscle contraction leads to more resilient activation of the parasympathetic response than either alternating contractions or breathing alone, which may help explain the stress reducing benefits of mind–body disciplines.
Article Publication Date: 13/01/2022
DOI: 10.1002/smi.2887
