This randomized controlled study investigates the effects of sport-specific training on aerobic adaptation and circulating biomarker responses in trained combat athletes. Exercise induces systemic physiological adaptations through signaling molecules known as exerkines, including myokines and adipokines, which mediate communication between skeletal muscle and other metabolic organs.

Forty trained male kickboxers are randomly assigned to either an experimental training group or a control group. The experimental group performs an eight-week sport-specific conditioning program in addition to regular technical training, while the control group maintains their usual training routine.

Aerobic capacity is assessed using maximal oxygen uptake (VO₂max). Blood samples are collected before and after the intervention to determine circulating levels of exercise-responsive biomarkers, including myostatin, irisin, apelin, brain-derived neurotrophic factor (BDNF), fibroblast growth factor-21 (FGF21), and adiponectin.

The primary objective of the study is to evaluate whether changes in circulating biomarker responses are associated with improvements in aerobic performance. The findings may provide insight into the molecular mechanisms underlying exercise-induced physiological adaptation in combat athletes.

Physical exercise induces complex physiological adaptations that involve coordinated responses across multiple organ systems. In recent years, increasing attention has been directed toward circulating signaling molecules collectively referred to as exerkines. These molecules include myokines and adipokines that are released during or after exercise and contribute to communication between skeletal muscle, adipose tissue, the liver, and the central nervous system. Through these signaling pathways, exercise influences metabolic regulation, mitochondrial remodeling, inflammation, and tissue adaptation.

Combat sports such as kickboxing require repeated high-intensity efforts interspersed with short recovery periods. These demands place substantial stress on both anaerobic and aerobic energy systems. Consequently, aerobic capacity plays an essential role in maintaining performance and supporting recovery during repeated bouts of high-intensity activity.

Although improvements in aerobic performance following structured training programs are well documented, less is known about the molecular mechanisms that accompany these adaptations in combat sport athletes. Emerging evidence suggests that exercise-responsive biomarkers such as myostatin, irisin, apelin, brain-derived neurotrophic factor (BDNF), fibroblast growth factor-21 (FGF21), and adiponectin may play important roles in regulating metabolic adaptation and muscle remodeling.

The present randomized controlled trial aims to investigate whether coordinated changes in circulating myokine-adipokine responses are associated with improvements in aerobic capacity in trained combat athletes. Forty elite male kickboxers are randomly assigned to either an experimental training group or a control group. The intervention group performs an eight-week sport-specific conditioning program three times per week in addition to regular technical training, whereas the control group maintains their habitual training routine.

Aerobic capacity is assessed using maximal oxygen uptake (VO₂max) measured during a graded treadmill exercise test with respiratory gas analysis. Venous blood samples are collected under fasting conditions before and after the intervention to evaluate circulating biomarker responses. Biomarkers are analyzed using enzyme-linked immunosorbent assay (ELISA) techniques.

The primary outcome of the study is the change in VO₂max following the training intervention. Secondary outcomes include changes in circulating concentrations of myostatin, irisin, apelin, BDNF, FGF21, and adiponectin. The study also examines associations between biomarker changes and aerobic performance adaptation.

This study may contribute to a better understanding of the physiological mechanisms underlying exercise-induced adaptation and provide insight into how circulating biomarker responses may reflect training responsiveness in combat sport athletes.

Inclusion Criteria:

• Male combat sport athletes aged between 18 and 25 years
• Minimum five years of competitive kickboxing experience
• Regular participation in training at least five days per week
• Currently competing at the national level

Exclusion Criteria:

• Musculoskeletal injury within the previous six months
• Cardiovascular or metabolic disease
• Use of medications or supplements that may affect metabolic or hormonal responses
• Participation in additional structured conditioning programs during the study period

Individual participant data may be made available to qualified researchers upon reasonable request to the corresponding author, following publication of the study results and in accordance with institutional policies and ethical guidelines.