My main research interests are in the health benefits of exercise in general, and the effects of high-intensity interval training (HIT) in specific. HIT has rapidly gained in popularity over the past decade, and is often promoted as a time-efficient alternative to aerobic exercise. However, although the health benefits of HIT in lab-based studies are generally at least as good as or better than those associated with aerobic exercise, commonly used HIT protocols are less time-efficient than generally suggested and far too strenuous to be viable as exercise interventions for sedentary populations. In my research I address the question why HIT is so effective at improving health markers, and I use this information to attempt to ‘optimise’ HIT protocols by making them shorter and easier while retaining the health benefits. Our current working hypothesis is that the rapid glycogen breakdown during ‘supramaximal’ sprints is one of the main stimuli for the adaptations to HIT, and that therefore fewer and shorter sprints should be effective. Based on this hypothesis, we have developed an effective HIT protocol that is genuinely time-efficient (10 minutes per session / 3 sessions per week) and manageable (ratings of perceived exertion similar to those with moderate intensity exercise). This protocol, termed reduced-exertion HIT (REHIT) has great potential to remove many of the barriers that prevent sedentary individuals from reaping the benefits of exercise.