This is a very promising small scale study looking at the effects of caffeine on tolerance to high intensity workload. The study shows that those who took 5mg of caffeine per kg were able to train at a high intensity level for 30% longer than those who didn’t take caffeine. The caffeine group also burned 40% more calories.
This suggests caffeine maybe beneficial in enabling people to maintain their “peak exercise cardiorespiratory and muscular functions for a longer duration and do so while achieving a greater energy expenditure. This opens the possibility to combine high-intensity exercise and caffeine in exercise training programs designed with the intent to maximize the exercise-induced health benefits and athletic performance.”