The effects of caffeine or caffeine-based energy drinks on the recovery of autonomic nervous system balance after exercise have been the subject of several studies which yielded inconclusive results. In a recent study by Porto et al., the impact of a caffeine-based energy drink on heart rate variability (HRV) before and after a moderate aerobic exercise (running on a treadmill) has been studied in a randomized, crossover trial on healthy and active young males. It was concluded that an energy drink consumed before exercise did not affect HRV indices during post-exercise recovery. However, this conclusion is somewhat inconsistent with the reported data and hence may be misleading. Here, I discuss the shortcomings of that study and point out some inaccuracies in the reported results. Considering the above, it appears that energy drink consumption may affect some HRV indices after exercise, at least those related to high frequency changes in the autonomic activity.