RUNNING HEAD: FINGER TAPPING ON HEART RATE VARIABILITY. Effect of Finger Tapping on Heart Rate Variability. Derek Leo

Transcription

1 Effect of Finger Tapping on Heart Rate Variability Derek Leo University of Wisconsin Milwaukee

2 Though finger tapping has widely been used for coordination tasks, this is the first study to investigate finger tapping as a relaxation technique. This study will use heart rate and heart rate variability (HRV) as an index of stress and relaxation. This experiment will determine if finger tapping can be utilized to increase HRV by lowering heart rate. Using Biopac MP35 to measure cardiac activity and respiration, we instructed subject to start finger tapping at a steady pace, then gradually slow down at fixed increments; the condition lasted 6 minutes in total. Results showed that as the participant slowed down his finger tapping, his heart rate tended to decrease as well. Further analysis concludes that the subjects showed an increase in heart rate variability as well; this suggests that finger tapping can help individuals cope with stress by increasing their heart rate variability. Participant also wore a Polar watch, which is an ambulatory measuring device, to measure heart rate and R-R intervals (HRV) during daily activities.

3 Introduction The rate at which the heart pumps blood throughout the body is influenced by innumerable factors, just as any other process, but scientists frequently attribute much of it to the vagal branch of the autonomous nervous system (Hassett & Danforth, 1982). The autonomic nervous system regulates various metabolic functions such as respiration, heart rate, perspiration, salivation, etc. The vagal branch is composed of the sympathetic (SNS) and parasympathetic nervous systems (PNS), respectively, which can often act as positive and negative feedback mechanisms. The PNS is dominant in determining heart rate at rest, as it employs the neurotransmitter acetylcholine, which acts faster than the SNS s norepinephrine (Appelhans & Luecken, 2006). Because the system governing heart rate is the same one governing many other bodily functions, there is inherently a link between many of those processes. Because of the potential for advancements in both physiology and psychology, there has been a recent trend of research involving the cardiac-somatic relationship (Obrist et al., 1970). Heart rate variability has since become an increasingly common noninvasive physiological measure for regulated emotional responses (Hasset & Danforth, 1982). Heart rate has been strongly linked with social behaviors as well (Wascher et al., 2008; Graziano et al., 2007). Recent research has shown correlations between HRV and social traits, as well as lower stress and anxiety levels (Appelhans & Luecken, 2006). Heart rate variability is the phenomenon caused by the discrepancy in the time it takes the PNS' and the SNS' neurotransmitters to take effect, though it is a matter of seconds (Appelhans & Luecken, 2006). Heart rate variability is measured by

4 R-R intervals, which are essentially the peaks on the graph of a heart beat waveform, or an electrocardiogram (ECG). Thus, distance between R-R intervals can reflect the dominance of the PNS or SNS (Yasuma & Hayano, 2004). As heart rate decreases, the R-R intervals increase, indicating an increase in HRV. As it is still relatively new as a measure, there are still issues with methodology involving HRV (Denver et al., 2007; Fowles, 1982; Grossman et al., 2004; Ritz & Dahme, 2006). Despite some skepticism, heart rate variability has seen use as an index of anxiety or stress in several studies in recent years, offering support for its convergent validity (Chafin et al., 2008, Ottaviani et al., 2008; Sarang & Telles, 2006; Segerstrom & Nes, 2007; Utsey & Hook, 2007). Though understanding the implications of heart rate variability is important, understanding why the autonomic flexibility represented by HRV relates to regulated emotional responding would be just as prudent. Due to its relatively recent development, there is still much to learn about the mechanics of the ANS' influence on HRV and vice versa. Even so, there is a respectable body of research behind the cardiac-somatic relationship; there are two main theories regarding this relationship, the polyvagal theory fronted by Porges (1997) and the neurovisceral integration model outlined by Thayer & Lane (2000). The polyvagal theory describes the evolutionary framework of the autonomic nervous system, emphasizing the phylogenetic and functional significance of the ventral vagal complex, which refers to the most recently acquired component of the ANS. The theory states that the ventral vagal complex is the first stage to acquire myelinated sheaths, dramatically increasing speed so the vagus can rapidly withdraw and reinstate its

5 inhibitory influence on sinoatrial node activity. That is, since it's faster than the rest of the ANS, it's better able to regulate its inhibitory effect on heart rate. The ventral vagal complex is also indirectly connected to various cranial nerves that are significant in mediating many social behaviors; these connections offer a mechanism by which the ANS, specifically the vagal branch, can coordinate cardiac activity with relevant social behaviors (Porges, 1997, 2001). Taking a broader look at the nervous system, the neurovisceral integration model relates HRV with regulated emotional responding through a dynamical systems perspective (Thayer & Lane, 2000). The theory asserts that large-scale patterns, such as regulated emotional responding, are products of several smaller systems, such as higher brain systems, interacting. This differs from the polyvagal theory in that instead of one specific system controlling regulated emotional responding, the neurovisceral integration model theorizes an array of systems influencing it (Porges, 1997; Thayer & Lane, 2000). There is less emphasis on evolutionary neurobiology, though dynamical systems and evolutionary frameworks appear to be complementary rather than contradictory (Kenrick, 2001). While there is much focus on researching the cardiac-somatic relationship, researchers are also paying attention to the respiratory-cardiac relationship. Respiratory sinus arrhythmia (RSA) refers to the synchrony between breathing and heart rate variability, specifically PNS inhibition during expiration and SNS excitation during inspiration (Yasuma & Hayano, 2004). Basically, the heart rate accelerates during inspiration and slows down during expiration (Eckberg, 1983). Thanks to the strong link

6 between respiratory sinus arrhythmia and heart rate variability, RSA has become established as a physiological measure as well (Diest et al., 2006; Hirsch & Bishop, 1981; Porges, 2006). As with HRV, however, there are also some methodological issues plaguing the use of RSA as a measure (Grossman & Taylor, 2007; Grossman et al., 2004). Like with heart rate variability, there is some debate over the causes behind respiratory sinus arrhythmia; though unlike with HRV, the two camps in RSA research are mutually exclusive. Porges (1997, 2001) posits that, fitting in with his polyvagal theory, breathing is a psychosomatic phenomenon. Since part of the nervous system helps control it, it must be governed by at least some psychological activity. Grossman and colleagues occasionally criticize his theory, however, calling attention to possible confounds such as respiratory parameters, tidal volume and physical activity (Grossman et al., 1991; Grossman & Taylor, 2007). Furthermore, he questions the theory itself, including the proposed phylogenetic model and even challenges the external validity of Porges' simultaneously published paper that is, the sample is biased and not generalizable (Berntson et al., 2007; Denver et al., 2007). He emphasizes the significance of respiratory rate on RSA, a variable that is often overlooked (Grossman & Taylor, 2007). Finger tapping has seen wide use in experiments involving coordination tasks, effective because it is a relatively pure neurologically driven motor task (Kiziltan et al., 2006; Liu et al., 2006). Finger tapping has also been used as an example of entraining a motor process to a physiological process (Kirby et al., 1990; Wilke et al., 1975). It is

7 therefore possible to synchronize a motor process such as finger tapping to a physiological process such as heart rate or respiration. Despite this, finger tapping has never seen use as a relaxation technique; however, heart rate variability (and respiratory sinus arrhythmia) has seen use in at least one experiment studying relaxation techniques, which also serves as an example of using motor processes to influence physiological processes (Sarang and Telles, 2006). Methods For this search, I used PsychINFO with PsychARTICLES. I mostly used words such as psychophysiology, cardiac, motor process, emotional responding, heart rate variability, respiratory sinus arrhythmia, and whatever synonyms thereof, in various orders connected by the boolean operator and. Each string would typically produce between results. Discussion The use of finger tapping as a relaxation technique has never been studied, but shows potential as a simple, quick way to cope with stress. Heart rate variability, and consequently respiratory sinus arrhythmia, have already been widely implicated in stress research, and have even seen use in coping research. Finger tapping, likewise, is often a way to study many psychological phenomena, including stress.

8 Though there are still some issues with HRV and RSA, further research will inevitably clear them up. It is natural for a newly developed measure to have methodological issues, and only promotes more research.

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