Research and application in sport and exercise psychology (SEP) has relied heavily on psychophysiological applications. Heart rate (HR), blood pressure (BP), skin conductance (SC), and measurement of brain activity through sophisticated techniques such as positron-emission tomography (PET), electroencephalography (EEG) and magnetoencephalography (MEG), and functional magneticresonance imaging (fMRI) are only a few of the many psychophysiological measures that have been successfully used to better understand psychological phenomena and clarify mechanisms in exercise and sport settings. For instance, studies examining the relationship between arousal and performance in sport have relied heavily on HR in order to classify individual performance at various levels of physiological activation or arousal. This area of research has led to the idea that individuals perform best when they are at an optimal level of arousal, not too over and not too under-aroused. Physiological measures have also been employed in exercise psychology to better understand the effects of exercise on a wide variety of psychological and mental health outcomes including mood, anxiety, depression, cognitive function, and stress reactivity. In all of these studies, subtle changes in sensitive physiological measures are used to infer changes in readiness to perform or psychological state. These subtle physiological responses are believed to be a function of the demands of a situation or particular stimuli, an individual’s predisposition to respond in a specific fashion, and the interaction between the two. Individual response stereotypy (IRS), or the tendency of individuals to evidence particular physiological response patterns from one condition or situation to another, is an important consideration in all studies or applications incorporating psychophysiological measures. The construct of IRS, also referred to as autonomic response patterning, has led to a growing recognition that the psychological and health significance of certain psychophysiological states are better reflected by the overall pattern of activity across multiple measures of physiological state, rather than from an acute response or sensitive change across only one or a select group of response domains, such as fluctuations in HR or SC. Complex patterns of physiological responses, which are determined by multiple factors, are thus best studied by incorporating multiple measures of physiological responding.
According to IRS, some individuals will respond to certain situations or conditions (e.g., anticipation of an upcoming event, performance of a difficult cognitive task, drawing of blood from the finger, rest) with the greatest degree of activity in the same physiological measure, regardless of the situation or stressor. This is particularly relevant for studies or applications that rely only on a few or unitary situations and response measures. As an example, in the area of stress reactivity, researchers have been interested in determining whether exercise or fitness are associated with blunted or altered cardiovascular responses to stress. When assessing BP responses to stress following acute aerobic exercise, it is important to determine not only baseline BP values (in order to assess change in stress-related BP following exercise) but also any individual difference variables that might influence BP responding. Individuals with borderline hypertension or essential hypertension tend to respond to stressful situations with greater increases in BP, particularly when compared to normotensive individuals. Assessing hypertension status would therefore be important. It is also important to note that individuals differ widely in both resting (tonic) and task-related (phasic) physiological responses. Understanding the factors that predispose some individuals to respond in unique ways helps inform the design of research studies as well as understand for whom and under what situations one person may perform optimally or realize the greatest benefits from exercise. This individual, unique pattern of responding has led to IRS being conceptualized as a physiological trait, or an enduring disposition of the body to show specific elicited physiological states or responses.
Although not all studies are in agreement, the notion of IRS points to several important implications. First, it is important to realize that individuals do not vary haphazardly in their physiological reactivity in a given response measure, nor do they vary haphazardly in their pattern of reactivity. Rather, some individuals may respond with maximal physiological activation in the same response measure or to a particular stimulus while another may be considered a low responder or nonresponder. Also, a strong tendency exists for a unique pattern of physiological response to be reproduced from situation to situation. This is so even though the physiological and psychological demands of the different situations may be unrelated. Second, IRS has resulted in a better understanding of the specific situational factors, familiarity with the situation, and range of behavioral choices that contribute to the expression of physiological responses. These factors can be used to strengthen future experimental designs and justify caution in oversimplifying physiological measures. Future studies should aim to elucidate the specific determinants of these unique patterns of response and consider IRS and situational demands simultaneously. The problem of IRS does not currently appear to be a serious concern as long as careful consideration is given to the number and selection of physiological responses to be measured in psychophysiological studies. Also, a focus on IRS highlights the importance of studying individual differences in SEP research.
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- Stern, R. M., Ray, W. J., & Quigley, K. S. (2001).Psychophysiological recording (2nd ed.). New York: Oxford University Press.