Similarly, the second component of energy balance, energy intake, is limited by the accuracy of self-report, or in limited publications, weighed-diet records. Even when weighed-diet records are employed, one should consider the influence the recording process has on “real” intake. Therefore, there still remains a need for quantifying the actual energy intake and use of real athletes. The development of “nanotechnology” may significantly advance field-based measurement of energy flux. In addition, it is now apparent that cells respond to energetic signals. Changes in ATP, or more accurately the ratio of adenosine monophosphate (AMP) to ATP, can initiate adaptive changes in the cell. An important next step is to determine how the athlete can design his or her training to maximize the positive adaptive responses of this pathway or others. One interesting study design has subjects exercising in the glycogen-depleted versus glycogen-replete state. The findings from these studies will certainly stimulate more studies exploring the cellular signals of sport adaptation. Finally, scientists must go beyond describing what athletes do and continue to question established paradigms of exercise training by introducing novel strategies. For example, recent studies document similar endurance-training adaptations from multiple high-intensity exercise bouts as from prolonged submaximum exercise.These studies challenge the long-held notion that long-duration exercise is needed for increased aerobic exercise performance. However, these studies also open an opportunity to examine how one might address issues of energy balance when performing such a small absolute volume of exercise.
