This report provides an overview on the present knowledge on intramyocellular lipids (IMCL) and their dynamics in the course of interventions with physical activity of variable type and intensity in different population groups, as accessible by examinations using non-invasive volume-selective 1 H magnetic resonance spectroscopy (1 H MRS). IMCL serve as energy source in skeletal muscle for fat oxidation in the mitochondria and became intensively studied after discovery of their relation with insulin sensitivity. While baseline levels of IMCL concentration have been shown to be mainly dependent on the metabolic status (insulin sensitivity), on the level of training and on fibre composition in the muscles, studies applying different physical activity protocols revealed the dynamic of their depletion and replenishment. From the findings in human studies, it can be concluded that IMCL levels are potentially useful markers for monitoring metabolic adaptation of skeletal muscle to sportive activities and training.