Active Voice: Does Caffeine Enhance Tolerance to High-Intensity Exercise?

By Adriano E. Lima-Silva, Ph.D., and Romulo Bertuzzi, Ph.D.

Adriano E. Lima-Silva, Ph.D. Romulo Bertuzzi, Ph.D.
Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.

Adriano E. Lima-Silva, Ph.D., is a researcher at the Technological Federal University of Parana, Brazil. He is leader of the Human Performance Research Group and a level 1D researcher with the National Counsel of Technological and Scientific Development, Brazil. His research focuses on strategies to improve exercise performance, including nutritional intervention to delay fatigue and augment exercise training adaptations. He has been a member of ACSM since 2010.

Romulo Bertuzzi, Ph.D., is a professor at the University of Sao Paulo, the leader of the Endurance Sports Research Group (GEADE-USP), and a level 2 researcher with the National Counsel of Technological and Scientific Development, Brazil. His research has focused on understanding the limiting factors for endurance performance and their crucial role in designing effective training programs.

This commentary presents the authors’ views on the topic of their research article, which they and their colleagues authored. Their paper appeared in the January 2018 issue of
Medicine & Science in Sports & Exercise® (MSSE).

The lack of free time in modern life is a factor that limits participation in exercise and adherence to recreational athletic training. Because of this, a single short-duration, high-intensity exercise (around five minutes) that challenges the heart, lungs and muscles to work maximally has recently been considered as a time-efficient alternative to promote health and performance benefits. It also is likely that those who can sustain exercise intensity at higher fractions of their maximal oxygen uptake may be able to develop better training adaptations. In fact, training at or near maximal oxygen uptake might place maximal stress on the physiological processes and structures that limit maximal oxygen uptake, thereby achieving the optimal stimulus for training adaptation.

In our study, as reported in the January 2018 issue of MSSE, nine healthy men cycled until exhaustion at approximately 90 percent of maximal oxygen uptake after ingesting either caffeine or a placebo, in a randomized, counterbalanced, double-blinded design. We demonstrated that caffeine ingestion at a dose of five milligrams per kilogram of body weight (corresponding to about three five-ounce cups of coffee for a 70-kilogram person), taken one hour before the exercise, can increase tolerance time at the high-intensity load. Time to exhaustion for subjects was 30 percent longer with the caffeine condition as compared to placebo and it was accompanied by a larger fraction of the energy expenditure being achieved by aerobic rather than anaerobic pathways. Consequently, the total energy expenditure during exercise was approximately 40 percent greater following caffeine ingestion. Also, in the caffeine condition, exercise duration at the maximal oxygen uptake was longer and the subjects achieved higher values for peak heart rate and ventilation at end-exercise.

These findings suggest that caffeine enables exercisers to maintain 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. Although high-intensity exercise has been gradually incorporated into training routines, it may be difficult for non-athletes to tolerate this method of training. Caffeine might add benefit by increasing the tolerance for this type of exercise. In addition, as caffeine seems to increase total energy expenditure, caffeine might have the potential to be used in training routines that have the goal of reducing body weight. Further studies combining caffeine and high-intensity training will be necessary before its large use to improve training-induced adaptations.