Purpose Athletes have presented a deficiency in relative energy in recent years, which calls for appropriate nutritional guidance based on the estimated energy requirement (EER)—the target amount of daily energy intake (EI). The calculation of EER requires longitudinal physical activity level (PAL) data, which has received insufficient attention. Therefore, this study aimed to clarify the changes in PAL by training periodization using the doubly labeled water (DLW) method, combined with the current status of EI by competition characteristics. Methods The participants comprised four male sprint athletes and five male endurance athletes at the national level. The experimental periods were normal training (NT) and tapering training (TT) periods. PAL was measured using the DLW method, and EI was measured by the dietary record method. Results PAL of the sprint athletes in the NT periods was significantly higher than in TT periods. EI had no significant differences between the two periods. PAL and EI of the endurance athletes had no significant differences beteen the two periods. Conclusions These findings indicated that in sprint athletes, different PAL was observed between the two periods, with the TT period suggesting a lower value than the NT period. In endurance athletes, it had similar PAL values between the two periods. This suggests that the degree of influence of the training period on PAL may vary depending on the athletic events. Furthermore, the EI was not adjusted for changes in PAL, and the participants observed the status of energy-deficient regardless of discipline or training period.
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