Is meditation always relaxing? Investigating cardiovascular activity and subjective experience during training of three types of meditation

Meditation can be regarded as a kind of mental training, and may thus be linked to increased effort and physiological arousal. Such definition is in contrast to a widely held belief that meditation mainly leads to relaxation associated with lower effort and physiological arousal. However, effects of meditation on effort and physiological arousal may vary depending on the type of meditation, degree of mental effort, and amount of training. In the current study, we therefore assessed heart rate (HR), high-frequency heart rate variability (HF-HRV) and subjective ratings of effort and likeability during three types of meditation varying in their cognitive and attentional requirements, namely breathing meditation (BM), loving-kindness meditation (LKM) and observing-thoughts meditation (OTM). As part of a one-year longitudinal mental training study called the ReSource project, participants practiced each type of meditation exercise on a daily basis for 3 months. In line with our hypotheses, HR and effort were higher during LKM and OTM compared to BM. With training over time, HR and likeability increased, while HF-HRV and the subjective experience of effort decreased. The increase in HR and decrease in HF-HRV over time was stronger for LKM and OTM as compared to BM. The current study therefore suggests that core meditations aiming at improving compassion (LKM) and meta-cognitive skills (OTM) require effort and are associated with higher physiological arousal as compared to BM. Overall, these findings can be helpful in making more specific suggestions about which type of meditation is most adaptive for a given context and population