Neuromuscular, cardiovascular, and cortical responses to heart rate variability biofeedback

Background Heart rate variability biofeedback (HRV BFB) is a paced breathing scheme that triggers resonance in the cardiovascular system. Whilst HRV BFB approaches have been administered in performance enhancement settings, there seems to be a scarcity in systematic literature investigating performance parameters under HRV BFB. There is also no meta-analysis that examined the effects of HRV BFB on physiological indices. In addition, there has been no study that explored neuromuscular function in HRV BFB. Lastly, there have been limited underpinnings in vagal afferent pathway with HRV BFB. Aims The overarching aim of this thesis was to carry out a series of pilot studies examining various physiological indices under HRV BFB. To investigate this aim, five studies were undertaken. The purpose of the first study was to conduct a systematic review on the effect of HRV BFB on gross and fine motor performance of athletes. The objective of the second study was to administer a systematic review and meta-analysis on the effects of HRV BFB on heart rate variability and respiration of athletes. The third study aimed to determine the effect of acute HRV BFB on soleus motoneuron excitability using H-reflex. The fourth study aimed to investigate the effect of HRV BFB on muscle sympathetic nervous activity (MSNA). The purpose of the fifth study was to explore the effect of HRV BFB on vagal afferent pathway utilising heart evoked potentials (HEP). Results Study One: The influence of HRV BFB in fine and gross motor skills in athletes demonstrated conflicting findings. Study Two: HRV BFB reduced the respiration rate of athletes. Study Three: HRV BFB facilitated reduction in soleus motoneuron excitability. Study Four: An acute HRV BFB decreased MSNA compared to spontaneous breathing. Study Five: Significant HEP differences at fronto-parietal (Fp2), frontal (F3, Fz) central (C4), parietal (P7, Pz), occipital (O1, Oz, O2), and parieto-occipital (PO1, PO2) existed between HRV BFB and CON. Specifically, HRV BFB posted higher HEP at Fp2, F3, Fz, C4, and P7 than CON. However, HRV BFB demonstrated lower HEP at Pz, O1, Oz, O2, PO1, Pz, and PO2 compared to CON.