Interleukin-6 and cortisol responses following a shortand long-term cycling test in team athletes with different cardiorespiratory fitness levels

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Karaduman E., Avcı B., Eliöz M., Çakmak E.

BMC SPORTS SCIENCE, MEDICINE AND REHABILITATION, cilt.18, sa.1, ss.1-15, 2026 (SCI-Expanded, Scopus)

Özet

Background This study investigated the effects of short- and long-term cycling exercise on salivary cortisol and

IL-6 responses in team athletes with varying cardiorespiratory fitness levels.

Methods Twenty-seven athletes were categorized into three fitness groups based on estimated VO2max: very

poor/poor (V/P), fair/good (F/G), and excellent/superior (E/S). Participants completed two cycling tests in shortterm

(ST) maximal and long-term (LT) submaximal conditions, with saliva samples collected pre-exercise and

at 0 and 30 min post-exercise to measure cortisol and IL-6 levels. Preliminary psychological assessments for

anxiety and depression were also conducted.

Results Findings showed no significant changes in cortisol levels across conditions or fitness groups (p > 0.050).

However, IL-6 levels increased significantly post-exercise in both ST (36% at post-0 and 116% at post-30) and

LT (67% and 151%, respectively) conditions (time effect: F = 47.65, p < 0.001), with a more pronounced increase

following LT cycling (condition effect: F = 9.22, p = 0.005). Notably, athletes with lower fitness (V/P) exhibited

greater IL-6 responses compared to higher fitness groups (F/G and E/S) in both exercise conditions (p < 0.050).

Hierarchical regression analysis identified VO2max as a significant negative predictor of cortisol (post-0: β=-

0.765, p < 0.001) and IL-6 responses (post-0: β=-0.618, p = 0.001), explaining up to 45% and 42% of the variance,

respectively.

Conclusion In conclusion, IL-6 responses to cycling exercise are influenced by exercise intensity and cardiorespiratory

fitness, with long-term exercise eliciting stronger inflammatory responses, especially in less fit athletes.

These results emphasize the importance of considering fitness levels when evaluating exercise-induced neuroimmune-

endocrine responses and support individualized training programs tailored to optimize inflammatory and

hormonal adaptations.