thetic nervous system. 2.2 Metabolism Researchers Telles et al. (2015) conducted a study on HFYB and the effects on metabolism in experienced practitioners and evaluated the effects on carbon dioxide output, oxygen uptake, and ventilation. They understood that autonomic nervous system alterations can influence oxygen consumption and energy expenditure, and that HFYB has been recorded to affect autonomic variables and increase oxygen consumption with different effects compared to other hyper-metabolic states. Telles et al. (2015) compared participants (n=47) engaging in HFYB and BAW, with a control group (n=20). It was found that, along with the increased ventilation, the HFYB induced a hypermetabolic state (34.6 percent increase in oxygen consumption). As breath frequency increased, tidal volume decreased. Blood chemistry data showed that arterial carbon dioxide levels were reduced as expected with increased ventilation, but without hyperventilation symptoms. After the HFYB, ventilation returned to baseline, an effect contrasting with other hypermetabolic states that characteristically follow increased ventilation (Telles et al. 2015). With oxygen levels returning to baseline after the practice, the findings by Telles et al. (2015) indicated that the abdominal work involved in HFYB did not result in an oxygen debt as would be otherwise expected. The researchers suggested that this could be attributed to the relaxed mental state that previous studies have reported to occur during and after HFYB based on EEG recordings. Telles et al. (2015) suggested that HFYB could be used to increase energy expenditure without inducing the increased ventilation and oxygen debt that typically result from mental and physical exertion. They further noted a possible clinical application with respect to treating stressrelated illnesses and hypometabolic states (Telles et al. 2015). The results of all three of these studies (Raghuraj et al. 1998; Telles et al. 2015; Telles and Singh et al. 2011) support the perception that HFYB reduces vagal modulation and can shift autonomic balance to the sympathetic nervous system, a balance associated with vigilance and wakefulness, without overt activation of the sympathetic nervous system, and with an immediate return to a relaxed state after the practice. The ability to energize and stimulate wakefulness, without exhaustion or over-excitation, and while maintaining a relaxed interoceptive state, suggests that HFYB is an intervention worthy of further study, particularly with respect to its potential application in therapeutic settings and as a preparation for meditation. 3 Measures of cognitive function 3.1 Reaction time and P300 latency A reduction in reaction time (RT) is understood to indicate an enhancement of corticalarousal, central nervous system processing ability, and sensory-motor performance (Bhavanani, Madanmohan and Udupa 2003). Bhavanani et al. (2003) measured auditory and visual RTs before and after twenty-two participants 40 Anna Andaházy – Gejza M. Timčák
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