Resolved UPW link status 13-Aug-20 MF There is increasing evidence that acute exercise can benefit new word learning. Several factors such as baseline learning abilities, exercise intensity and timing, have been identified as playing a role in the acute effects of exercise on new word learning. However, this has been mostly studied in healthy young adults and is yet to be comprehensively examined in healthy older adults. The overarching aims of this thesis were to review the acute effects of exercise on cognition in ageing and to further examine these effects on new word learning in healthy older adults. This was achieved by conducting a systematic review (chapter 2) and two randomised controlled trials – one investigating the effects of different pre-learning acute exercise intensities on new word learning (chapters 3-5) and one examining the effects of post-learning high-intensity exercise on new word learning (chapter 6). Chapter 2 systematically reviewed studies investigating the immediate effects of acute aerobic exercise on cognition in healthy older adults. Fifteen studies were included in this review, and cognitive domains examined included executive function and audio-visual perception. The majority of studies (n=14) showed a significant effect of acute aerobic exercise on at least one subsequent cognitive test. This review highlighted the benefits of acute aerobic exercise on cognition in ageing but also the limited number of cognitive domains investigated thus far, and the overall low methodological quality rating of studies, highlighting the need for additional comprehensive trials to further explore the acute effects of exercise on other cognitive domains. To address this gap, chapter 3 investigated the effects of moderate-intensity continuous exercise (MICE) and high-intensity interval exercise (HIIE), in comparison to an attention control condition (i.e., stretching), on immediate and delayed new word learning performance in healthy older adults. This study further examined whether these effects varied as a function of baseline learning abilities. Findings showed an overall effect of acute exercise on immediate new word learning performance; however, this effect varied as a function of baseline learning abilities and favoured MICE over stretching in older adults with lower baseline learning abilities. This advantage was not maintained when delayed retention of words was assessed one-week later and was not observed in higher baseline learners. Chapter 4 investigated acute exercise-induced changes in learning-related biomarkers (i.e., glucose, insulin, brain-derived neurotrophic factor (BDNF), apolipoprotein E and cytokines TNF-α, IL-1β, IL-6) and their relationship with post-exercise new word learning performance in healthy older adults with lower and higher baseline learning abilities. Blood samples were collected pre-exercise, post-exercise and post-learning and findings showed that regardless of baseline learning abilities, more sustained pre-post learning BDNF levels in the MICE group correlated with immediate word learning recognition reaction time. In higher baseline learners, pre-post exercise increases in glucose levels were observed in the HIIE group and related to immediate word recall and recognition accuracy. Pre-post exercise increases in insulin levels were also observed; however, no correlations with word learning performances were found. Exercise-induced changes in ApoE, cytokines IL-6, IL- 1β and TNF-α were not observed. Chapter 5 examined the use of post-exercise word learning strategies to support associative new word learning performance of healthy older adults with lower and higher baseline learning abilities. Healthy older adults used phonological, lexical, semantic and visual strategies to support their learning. There was increased use of visual strategies for lower baseline learners in the MICE group compared to those in the stretching and HIIE groups. However, this result was observed in a small sample and further investigations are required to verify an association between the use of visual strategies and post-exercise word learning success. Taken together, the results of chapter 3, 4 and 5 indicated that a single bout of MICE, when compared to stretching, benefits subsequent immediate, but not delayed, new word learning performance of healthy older adults with lower baseline learning abilities. This enhancement was not explained by exercise-induced changes in neurophysiological biomarkers, however, could potentially be related to the use of visual strategies. Chapter 6 investigated a different timing of exercise relative to word learning. The effects of post-learning HIIE, in comparison to stretching, were examined on the early and later stages of new word consolidation in healthy older adults with lower and higher baseline learning abilities. Results suggested no benefits of HIIE over stretching to enhance the early and later stages of new word learning consolidation in healthy older adults and did not suggest greater benefits for lower in comparison to higher baseline learners. Overall, the body of research included in this thesis suggested selective benefits of acute exercise on new word learning performance in healthy older adults. This work highlighted the impact of individual baseline learning abilities, exercise intensity and timing on word learning success and identified the need to further explore potential underlying mechanisms to better understand when and how acute exercise may influence cognition in ageing.