Training Status Modifies Muscle-Damage and Inflammatory Biomarker Responses During a 6-Week Moderate-Intensity Treadmill-Running Programme in Healthy Young Men: A Non-Randomised Controlled Study.

Abstract

Background: A single exercise session leads to increased muscle damage (CK and LDH) and inflammatory biomarkers (IL-6 and CRP), peaking in hours and returning to baseline over a 24-hour period, regular training induces a chronic anti-inflammatory adaptation. The magnitude of this biomarker response to repeated moderate-intensity treadmill exercise according to activity status remains not fully characterized.
Objective: This study was conducted to compare the levels of muscle damage markers; CK and LDH at baseline (t0), 3 weeks (t1) and 6 weeks (t2) following moderate intensity running exercise among healthy young men and to determine the levels of inflammatory biomarkers; IL-6 and CRP at baseline (t0), 3 weeks (t1) and 6 weeks (t2) following moderate intensity running exercise among healthy young men.
Methods: This study was a non-randomized, controlled design with 36 participants divided into four groups based on baseline physical activity levels: active-intervention, active-control, sedentary-intervention and sedentary-control (n = 9 per group). Active status ≥150 min/week of moderate intensity physical activity, and sedentary status < 120 min /week, within each group of participants were matched and assigned to intervention or control. The intervention consisted of a supervised 6-week exercise program (3 sessions per week) and adherence to the program was monitored through attendance (100%). The blood samples were taken at baseline, week 3, and week 6 between 07:00–09:00 pm, 24 h after the last exercise session to minimize acute post exercise effects. CK (primary score), LDH, CRP and IL-6 levels were measured. Mixed repeated-measures ANOVA (time × group), Greenhouse–Geisser correction (where sphericity was violated), and polynomial trend contrasts were used to analyze the data with a significance at p < 0.05.
Results: For all four biomarkers, there was a significant Time main effect (all p < 0.001), a significant Time × Group interaction (all p < 0.001), and a significant between-subjects Group difference (all p < 0.001). These effects were driven by the Sedentary-intervention group showed a marked transient rise at t1 followed by partial normalisation at t2: CK 107.72 ± 22.02 → 242.48 ± 47.84 → 140.89 ± 63.25 U/L; LDH 207.16 ± 38.48 → 345.52 ± 68.19 → 203.28 ± 73.31 U/L; CRP 0.85 ± 0.47 → 3.33 ± 0.65 → 1.23 ± 0.49 mg/L; and IL-6 3.27 ± 0.77 → 8.04 ± 1.15 → 2.49 ± 1.00 pg/mL. The Active-intervention, Active-Control, and Sedentary-Control groups were not significantly different over time. The interactions were carried by highly significant quadratic Time × Group components (CK F(3,32) = 22.75, η²p = 0.68; LDH F(3,32) = 87.11, η²p = 0.89; CRP F(3,32) = 261.81, η²p = 0.96; IL-6 F(3,32) = 263.70, η²p = 0.96; all p < 0.001).
Conclusion: In this small, non-randomized study, the sedentary-intervention group had showed significant change in CK, LDH, CRP and IL-6 levels at t1, followed by attenuation at t2, while The active-intervention, active-Control, and sedentary-control groups were not significantly different over time. These descriptive patterns are similar to the transient muscle-stress and inflammatory response to a novel running stimulus in sedentary individuals, and partial recovery during the programme.