A sedentary lifestyle has been linked to a number of metabolic disorders that have been associated with sub-optimal mitochondrial characteristics and an increased risk of premature death. Endurance training can induce an increase in mitochondrial content and/or mitochondrial functional qualities, which are associated with improved health and well-being and a longer life expectancy. It is therefore important to better define how manipulating key parameters of an endurance training intervention can influence the content and functionality of the mitochondrial pool. This presentation will focus on mitochondrial changes taking place following a series of exercise sessions (training-induced mitochondrial adaptations), and it will provide an in-depth analysis of the effects of exercise intensity and training volume on changes in mitochondrial content and mitochondrial respiratory function. Evidence will be presented that indicates manipulation of different exercise training variables promotes specific and diverse mitochondrial adaptations. Specifically: a) Training volume appears to be an important determinant of training-induced increases in mitochondrial content (an effect that may be driven by training duration), whereas exercise intensity appears to be a key factor of training-induced increases in mitochondrial respiration. b) Training-induced changes in mitochondrial content and respiratory function seem to be differentially regulated, and they are not necessarily associated to one another. c) High-intensity interval training at a relative exercise intensity ≥ 90% of the maximal aerobic power provides the greatest absolute increase in mass-specific mitochondrial respiration, whereas all-out sprint interval training appears to be the most efficient type of exercise to improve mitochondrial respiratory function in terms of total training volume and/or time. d) Mitochondrial adaptations to exercise training are rapidly reversed following different types of detraining; however, these can be maintained when a sufficient training stimulus is provided. Our recent results also indicate that the early molecular events in response to a single bout of exercise differ between high-intensity and high-volume exercise, and this may help to explain the different training responses. However, exercise-induced changes are not always predictive of training-induced adaptations, and possible explanations these discrepancies will also be discussed.