Exploring the Psychopysiological Indices of Perceived Effort and its Self-Regulation

Effort involves the application of physical and mental resources towards a task. Individuals perceive effort during task engagement like exercise with a conscious sensation of how hard, heavy, and strenuous the exercise consciously feels to drive the working muscles and for breathing. Accordingly, individuals' decisions are thought to be guided by their perceived effort. In turn, there are numerous psychophysiological characteristics that underpin the perceived effort phenomenon which can also play a role in the overall decision-making processes and self-regulation of behaviour. However, it is often difficult to capture the underlying mechanisms of decision-making processes due to their erratic and complex nature. Consequently, there is scant literature on the psychophysiological indices of set perceived effort intensities and underlying decision-making processes during self-regulation of perceived effort. Yet, a small sample of studies have demonstrated that concurrent mixed-methods/process-tracing approaches can delve more into complex decision-making processes involved with regulating perceived effort and exercise behaviour. Subsequently, the main aim of the present thesis was to explore the psychophysiological indices of perceived effort and its self-regulation.

This thesis comprises three separate studies. In Study 1, the reliability of a novel fixed perceived effort cycling task was investigated. Results demonstrated that a novel fixed perceived effort trial that corresponded ratings of perceived effort to a known physiological threshold was reliably produced over numerous bouts and elicited a consistent psychophysiological response for each perceived effort intensity. A following study (Study 2, Part A) also probed the psychophysiological responses associated with two intensities of fixed perceived effort. During these studies it appeared that physical outputs at a set perceived effort intensity would decrease over time to maintain the same perception of effort. Meanwhile, certain psychophysiological markers showed characteristic increases (e.g., heart rate) or decreases (e.g., affective valence) as the fixed perceived effort exercise progressed. As a result, specific intensities of perceived effort appear to exhibit different power output and psychophysiological responses in terms of magnitude and changes over time. This could possibly then be linked to different ways that perceived effort is self-regulated.

It was also of interest how individuals self-regulated during fixed perceived effort exercise. To achieve this, Study 2 utilised a think aloud protocol to understand the behavioural and cognitive self-regulatory strategies that were used by participants at different fixed perceived effort intensities (Part A) as well as any differences in self-regulation between experienced and inexperienced cyclists (Part B). Within Part A, it was found that there was a greater change in power output during the higher intensity fixed perceived effort cycle, signifying a greater amount of behavioural self-regulation. Furthermore, the activation of cognitive strategies was also greater in the higher intensity fixed perceived effort task. When assessing differences between experience levels of participants, there were no significant differences in power output or major secondary themes of the think aloud protocol suggesting participants of any experience level may self-regulate perceived effort similarly. However, closer examination of the primary themes from the think aloud data suggest experience level may affect the cognitive self-regulatory strategies that are used during a prolonged fixed perceived effort intensity exercise.

Finally, this thesis then explored any changes in self-regulation of perceived effort after an intervention which involved experimentally induced muscle pain. In addition, this study also incorporated the use of functional near infrared spectroscopy to assess the cognitive effort applied to activate cognitive self-regulation strategies during fixed perceived effort exercise. It was found that the presence of elevated muscle pain due to an intramuscular hypertonic saline injection cause a significantly lower power output than an isotonic placebo-control condition. In addition, near infrared spectroscopy data showed a greater change in deoxyhaemoglobin between condition suggesting a greater use of cognitive self-regulatory strategies as part of executive function when experiencing elevated muscle pain compared to a placebo-control.

Overall, this thesis firstly found a novel fixed perceived effort exercise to be reliable. Using this task paradigm, additional studies show that specific intensities of perceived effort seem to elicit different power output and psychophysiological responses in terms of magnitude (e.g., higher/lower between intensities) and changes over time (condition x time interactions). Subsequently, data concerning the self-regulation of perceived effort shows that participants employ a mixture of behavioural (i.e., changing power output) and cognitive (i.e., engaging in reappraisal and/or self-talk) strategies to self-regulate perceived effort. In addition, there was a difference in self-regulatory strategies between conditions which involved elevated muscle pain (hypertonic saline injection) or a no elevated muscle pain (isotonic saline injection). Therefore, the self-regulation of perceived effort is likely context dependent and there are also likely to be some individual preferences towards how perceived effort is self-regulated.