Pharmacological facilitation of physical activity behaviour: an experimental medicine approach

Physical inactivity is a global health problem. Despite a good understanding of the benefits of completing regular exercise, adherence rates at a population level are extremely low. An experimental medicine approach to health behaviour change was recently proposed, which prioritises an understanding of how, not just whether interventions are effective. The present study serves as the first application of this model to develop a physical activity behaviour change intervention. This thesis is comprised of eight studies in 6 experimental chapters, which are presented in two parts. Part I is focussed on understanding whether changes in perceptual responses to exercise, caused by caffeine, are sufficient to elicit a change in physical activity behaviour. Chapter 4 utilised a single-subject experimental design as a preliminary trial. We provided the first experimental evidence that pharmacological intervention can influence physical activity choice behaviour by manipulating feelings during and around exercise. In chapter 5, a group trial corroborated many of the psychological and perceptual effects of caffeine observed in chapter 4, whilst a qualitative exploratory analysis of the factors underlying exercise choice revealed that perception of effort was the primary determinant of exercise preference. chapter 6 investigated the metabolic effects of caffeine during high-intensity interval training (HIIT). Providing evidence to suggest that caffeine can elicit a dual function of increasing non-exercise thermogenic activity, as well as increasing metabolic activity during HIIT, without an increase in perceptions of effort and discomfort. The aim of Part II was to develop a preclinical model to measure the effects of pharmacological interventions on physical activity behaviour. In chapter 10 we determined an appropriate running wheel access paradigm. In chapter 11 we proved for the first time that caffeine does not elicit a significant increase in voluntary wheel-running activity during the active phase in mice. Whilst chapter 12 validated a method of pharmacologically inducing human sedentary-like behaviours in mice, and demonstrated the ability to completely reverse wheel-running suppression with caffeine administration. In sum, this thesis offers translational models, able to detect psychological and behavioural effects of pharmacological intervention, providing a platform from which to test the effects of alternative drugs, for trials at a pre-clinical and human level, on physical activity behaviour in the future

An all-out test to determine finger flexor critical force in rock climbers

Results: The ff-CF protocol resulted in the same force decay to a plateau seen in previous isometric critical torque and critical force tests. Linear regression analysis, adjusting for sex, revealed that CF% body mass explained 61% of sport and 26% of bouldering performance and W’ per kg body mass explained 7% sport and 34% bouldering performance. A combined model of CF% body mass and W’ per kg body mass, after adjustment for sex differences was able to explain 66% of sport climbing and 44% of bouldering performance. Conclusions: The results illustrate the relevance of the CF threshold in describing the fatigue resistance of the finger flexors of rock climbers. Given ff-CF ability to describe a considerable proportion of variance in sport climbing and bouldering ability we expect it to become a common test used by coaches for understanding exercise tolerance and for determining optimal training prescription

Effects of Caffeine Ingestion on Human Standing Balance: A Systematic Review of Placebo-Controlled Trials.

Caffeine ingestion may influence balance control via numerous mechanisms. Although previously investigated using various study designs and methods, here we aimed to create the first evidence-based consensus regarding the effects of caffeine on the control of upright stance via systematic review (PROSPERO registration CRD42021226939). Embase, PubMed/MEDLINE, SPORTDiscus and Web of Science databases were searched on 27 January 2021 to identify placebo-controlled trials investigating caffeine-induced changes in human standing balance. Reference lists of eligible studies were also searched. Overall, nine studies involving a total of 290 participants were included. All studies were moderate to strong in quality according to the QualSyst tool. Balance-related outcome measures were collected across a range of different participant ages, stances and sensory conditions. The results show that younger participants' balance was generally unaffected by caffeine ingestion. However, a significant balance impairment was observed following caffeine ingestion in all studies involving older participants (average age >65 years). Our results therefore suggest an age-dependent effect of caffeine ingestion on human standing. Further research into this effect is warranted as only one study has directly compared younger and older adults. Nonetheless, an important implication of our findings is that caffeine ingestion may increase fall risk in older adults. Furthermore, based on our findings, caffeine ingestion should be considered as a potential confounding factor when assessing human standing balance, particularly in older adults.N/

Anthropometry and performance characteristics of recreational advanced to elite female rock climbers

Despite climbing's popularity and an increasing number of female participants, there are limited anthropometric and performance data for this population. This study compares the characteristics of 55 experienced female climbers, divided into three categories (lower [ADV-L] and higher advanced [ADV-H] and elite [ELT]) based on self-reported ability. Data on climbing experience, body dimensions, body composition, flexibility, lower and upper-body power and finger strength were assessed. ELT climbers differed significantly from the ADV groups in age (Mean Difference [MD] = 8.8-9.8 yrs; despite smaller differences in years climbing MD = 1.6-2.4 yrs), greater climbing and hours training per week (MD = 3.0-3.7 h & MD = 0.9-1.6 h, respectively), and greater upper-body power (MD = 12.9-16.6 cm) and finger strength (MD = 51.6-65.4 N). Linear regression analysis showed finger strength and upper body power to be associated with ability, particularly when adjusting for descriptive and anthropometric variables (finger strength R2 = 53% and 45%; upper-body power R2 = 60% and 39% for boulder and sport, respectively). The findings support the importance of finger strength and upper-body power; changes in female anthropometric data over the last decade provide insight into the changing nature of the sport