The body has two energy delivery systems: "aerobic energy" that uses oxygen and "anaerobic energy" that does not use oxygen. Oxygen is used during exercise to produce energy from sugar and fat; however, in a short-distance running race where large kinetic energy is required in a short period of time, a metabolic mechanism called glycolysis works, which uses sugar as an energy source instead of oxygen. In the glycolytic system, lactic acid is produced as a metabolite, and as the exercise intensity gets closer to the maximum, lactic acid is increased and accumulated in the muscles. When lactic acid is accumulated more than a certain level in the muscles, the muscle acidity increases and people are no longer able to continue exercising.
The "aerobic energy" system can be trained with aerobic exercises such as jogging and aerobics, and as a result, endurance is increased. The "anaerobic energy" system can be trained with high-intensity interval exercises (for example in track and field, 200-meter runs 5 times).
Tabata regimen is a training program that can train two energy delivery systems simultaneously in a short period of time by giving 8 sets of intermittent exercise to exhaustion in a total of approximately 4 minutes, with 1 set of 20-second exercise and 10-second rest [References 1 and 2].

This study examined the effect of long-term intake of chlorella in combination with HIIE on muscle glycolytic and oxidative capacity as well as on exercise performance.

【Results】

After the end of the 6-week intake period, blood lactate levels at 1 minute after HIIE were significantly lower in the HIIE and HIIE+CH groups than in the Con and CH groups, and significantly lower in the HIIE+CH group than in the HIIE group (Table 1). The maximal number of HIIE training was significantly higher in the CH, HIIE, and HIIE+CH groups than in the Con group, and significantly higher in the HIIE+CH group than in the CH and HIIE groups (Figure 1). The PFK activities in both red and white muscles were significantly higher in the CH, HIIE, and HIIE+CH groups than in the Con group, and significantly higher in the HIIE+CH group than in the CH and HIIE groups (Figure 2 A and B). The LDH activity was significantly higher in the CH, HIIE, and HIIE+CH groups than in the Con group, and significantly higher in the HIIE+CH group than in the CH and HIIE groups in the red muscle, but no significant difference was observed in the white muscle between the groups (Figure 2 C and D). The expression levels of PGC-1α in both red and white muscles were significantly higher in the CH, HIIE, and HIIE+CH groups than in the Con group, and significantly higher in the HIIE+CH group than in the CH and HIIE groups (Figure 3). The CS and COX activities in the red muscle were significantly higher in the CH, HIIE, and HIIE+CH groups than in the Con group, and significantly higher in the HIIE+CH group than in the CH and HIIE groups, but no significant difference was observed in the white muscle between the groups (Figure 4 A, B, C, and D). For MCT1 and MCT4, the expression levels in the red muscle were significantly higher in the CH, HIIE, and HIIE+CH groups than in the Con group, and significantly higher in the HIIE+CH group than in the CH and HIIE groups, but no significant difference was observed in the white muscle between the groups. The expression levels of MCT4 in both red and white muscles were significantly higher in the CH, HIIE, and HIIE+CH groups than in the Con group, and significantly higher in the HIIE+CH group than in the CH and HIIE groups (Figure 5 A, B, C, and D).

Table 1. Blood lactate levels pre- and post- HIIE training

Values are expressed as mean ± SD. ^#P < 0.05 vs Con group at post-HIIE after intervention. ^$P < 0.05 vs CH group at post-HIIE after intervention. ^&P < 0.05 vs HIIE group at post-HIIE after intervention.

Figure 1. Effects of chlorella intake and/or HIIE training on maximal number of HIIE sets

Values are expressed as mean ± SD. ^#P < 0.05 vs Con group. ^$P < 0.05 vs CH group. ^&P < 0.05 vs HIIE group.

【Discussion】

The combination of HIIE training and chlorella intake resulted in a synergistic increase in LDH, PFK, CS, and COX activities in the red muscle, and a synergistic increase in PFK activity in the white muscle. Furthermore, there was a synergistic increase in the expression of MCT1, MCT4, and PGC-1α in the red muscle and a synergistic increase in the expression of MCT4 and PGC-1α in the white muscle. These results suggest that the increased ATP supply capacity due to skeletal muscle glycolysis and oxidative metabolism improved aerobic and anaerobic exercise capacity.
The results of this study indicate that the combination of HIIE training and chlorella intake improves aerobic and anaerobic exercise capacity and promotes muscle glycolytic and oxidative metabolism, particularly lactate metabolism.