Blood Biochemical Acute Daily Responses During an Intensive Training Microcycle: A Case Report of an Olympic Kayaker

Monitoring physiological responses to intensified training is critical in elite sport, yet evidence in world-class kayak paddlers remains limited. To assess biochemical and hematological acute responses during an intensified training microcycle in an elite flat-water kayaker, a 35-year-old Olympic-level kayaker was monitored across two consecutive 7-day microcycles (pre-intensified and intensified). During the intensified microcycle, fasting venous blood samples were collected over five consecutive mornings. Hematological, biochemical, and hormonal markers were analyzed using standardized laboratory procedures. Training intensification induced marked but physiological changes. From Monday to Tuesday, leucocytes increased from 5.7 to 7.3 × 10⁹/L (+28%), while creatine kinase (CK) rose from 291 to 602 U/L (+107%) and remained elevated (579-604 U/L). Serum iron decreased from 131 to 88 µg/dL (-32.8%) and remained below baseline throughout the microcycle. Triglycerides declined from 63 to 52 mg/dL (-17.5%) and stabilized thereafter. AST increased from 33 to 41 U/L (+24.2%) with minor fluctuations. Across the microcycle, cortisol rose from 522 to 575-578 nmol/L (+10-10.7%), whereas testosterone remained stable (29.4-31.2 nmol/L). Epinephrine increased from 13 to 37 ng/L (+184.6%). Erythrocytes, hemoglobin, and C-reactive protein remained stable. The intensified microcycle elicited substantial but controlled physiological perturbations, reflecting increased muscle stress and systemic load without evidence of maladaptation.