There are trillions of microorganisms living alongside us in our guts. Recent research has shown that this community, known as the gut microbiome, has a big influence on our health and wellbeing. Imbalances in the composition of the gut microbial community has been linked to several diseases including COVID, mental ill health, and diabetes. When the composition of the gut microbiome changes towards a less healthy one (called dysbiosis) this will, in turn, affect our health in a negative way. The composition of our gut microbiome remains fairly stable during adulthood, however, as we move into older age, there is a shift and its composition will change to a less healthy one; this is one of the reasons why older people can be more susceptible to diseases. Fortunately, there are several tools that we can use to improve our gut microbiome and one of them is exercise. Besides its well-known effects on our health, exercise has been shown to be able to improve the gut microbiome composition of younger people and those with certain metabolic diseases such as obesity. However, less is known about the effects of exercise on the gut microbiome of older adults. The aim of this study, therefore, is to assess the effects of a 12-week exercise intervention on the gut microbiome of physically inactive older adults. Hopefully, after this study, the investigators will have more information on whether exercise can be used as a tool to improve the gut microbiome of older adults therefore improving their overall health and quality of life.