Conclusions
This study demonstrates that acute HIIE effectively increases serum FGF-21, FSTL-1, cathepsin B, and BDNF compared to MICE. Therefore, the secretion of exerkines, including FGF-21, FSTL-1, cathepsin B, and BDNF may be exercise intensity-dependent.
Methods
Nine young men (24.0 ± 0.4 years old) performed 4 different experimental sessions at 1-week intervals: 1) a control session (CTRL; no exercise); 2) moderate-intensity continuous exercise (MICE, 55% HRR); 3) vigorous-intensity continuous exercise (VICE, 85% HRR); and 4) high-intensity interval exercise (HIIE, 4 repetitions of a 30-s of "all out" cycling workout followed by a 4-min recovery). Blood samples were collected at 4 different time points (pre-exercise, immediately post-exercise, 30 min post-exercise, and 90 min post-exercise).
Results
Serum FGF-21, FSTL-1, cathepsin B, and BDNF were higher in HIIE than in CTRL immediately post-exercise, and FSTL-1, cathepsin B, and BDNF were higher in HIIE than in MICE immediately post-exercise (P < 0.05). The AUC for FGF-21, FSTL-1, and BDNF was higher in HIIE than in CTRL, and the AUC for FGF-21 and BDNF was higher in HIIE than in MICE (P < 0.05). Furthermore, the change in blood lactate was positively correlated with the changes in all exerkines. Conclusions: This study demonstrates that acute HIIE effectively increases serum FGF-21, FSTL-1, cathepsin B, and BDNF compared to MICE. Therefore, the secretion of exerkines, including FGF-21, FSTL-1, cathepsin B, and BDNF may be exercise intensity-dependent.