When exercise bouts are repeated regularly, i.e. exercise training, adaptations occur enabling the muscles to tolerate exercise at higher intensities and/or for longer periods of time. At the cellular level the improved exercise capacity is related to an altered expression of proteins involved in both substrate transport across the sarcolemma as well as substrate metabolism inside the muscle cell. In respect to glucose metabolism it is interesting that exercise performed after training at the same moderate absolute intensity as before training elicits a diminished glucose turnover whereas when heavy exercise is performed muscle glucose uptake is in fact increased in the trained state. This might be related to the training induced increase in glucose transporter protein expression in skeletal muscle. This adaptation is also important for glucose handling in the post exercise period. For example, endurance training has been shown to improve insulin sensitivity in human skeletal muscle which likely is important for the training induced increase in glycogen levels. The phenomenon of exercise training improvement in insulin sensitivity is the basis for recommending physical activity as an important tool in prevention and treatment of insulin resistance. As an acute bout of exercise per se also is a potent factor improving insulin sensitivity, it is the current belief that the improved insulin sensitivity in response to training is a combination of the effect from the last bout of exercise as well as the effect of the training per se. The two effects may be mechanistically related to some extent but likely also partly unrelated. This is illustrated by the observation that the effects of training are long lasting whereas the effect of an acute exercise bout is of shorter duration. In addition, the effect of training exists even in the face of glycogen super compensation whereas the effects of acute exercise to some extent, but not fully, are related to glycogen re-synthesis. The long lasting effects of exercise training on insulin sensitivity are likely a consequence of changes in protein expression profile within the trained muscle fiber. The presentation will primary be based on recent human exercise training studies performed in our laboratory with data illustrating and specifying some of the above phenomena.