AEROBIC ADAPTATION AND BIOMARKER RESPONSES 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