Mitochondria are more than simply energy-making ‘factories’ within our cells; they are descendants of ancient bacterial species that integrate with the health of all body systems, most notably the gastrointestinal microbiome. They run on macronutrient ‘fuel’ from the diet, along with micronutrient co-factors for enzymatic facilitation of the energy pathways, and are heavily reliant on antioxidant membrane protection. When athletes exercise, the redox capacity of their enzyme antioxidant systems increase as part of the adaptive training response. However, this process is reliant on sufficient dietary nourishment, and if the training load becomes excessive, and recuperation strategies insufficient, the resultant oxidative stress can overpower these innate antioxidant systems over time. This can lead to cardiovascular pathology, as can be seen in some cases of ageing endurance athletes with heavy training loads. However, by paying attention to overall life load, training and recovery balance, and deep cellular and mitochondrial nourishment (including awareness of micronutrients and polyphenols), athletes should be able to maintain better health, support their athletic performance, and look forward to longevity in their sport and their life.