The Impact of Overtraining on Anxiety-Like Behavior and Tight Junction Proteins of the Blood-Brain Barrier in Mice.
Hwang E, Shin M, Park T, Kim JJ, Yi D, Park J et al. · Brain and behavior · 2026
Purpose: Overtraining Syndrome (OTS) is a chronic maladaptive condition characterized by persistent performance decline due to excessive training and inadequate recovery. OTS is associated with mood disturbances, but the underlying neurobiological mechanisms remain unclear. This study investigated whether a 6-week overtraining (OT) protocol induces anxiety-like behavior and changes in hippocampal BBB-related tight junction proteins in mice.
Methods: Eight-week-old male C57BL/6J mice were assigned to sedentary (SED, n = 5), moderate exercise (ME, n = 5), or overtraining (OT; downhill treadmill running, initially n = 10) groups and completed a 6-week training protocol. The final OT sample size was n = 4 after 6 of the 10 mice were excluded due to tail or hindlimb injuries. Endurance capacity was assessed using an incremental loading test (ILT). Anxiety-like behaviors were evaluated using the nest building test (NBT), open-field test (OFT), and elevated plus maze (EPM). Hippocampal tight junction (TJ) proteins zonula occludens-1 (ZO-1), occludin, claudin-5, as well as tumor necrosis factor-alpha (TNF-α) were quantified by Western blot analysis.
Results: After 6 weeks, endurance performance in the OT group significantly decreased from baseline (p
Conclusion: OT was associated with anxiety-like behavioral alterations and changes in hippocampal BBB-related tight junction proteins. Reduced expression of TJ proteins and increased neuroinflammation may contribute to affective symptoms observed in OTS. However, given the small final sample size in the OT group, these
Findings: should be interpreted with caution.