Study On Heat Shock Protein (Hsp72) Acting As A Monitoring Marker Of Overtraining

Objective : Presently , we are not clear about overtraining mechanisms-According to cytokine hypothesis of overtraining , the imbalance between exercise-induced injury/recovery is cause of overtraining. Followed by Steinacker et al compensating cytokine hypothesis of overtraining, proposed a model of a biphasic overtraining, peripheral mechanisms in the early overtraining and central mechanisms in the pronounced phases of overtraining, and cytokine links the early phase of overtraining and the pronounced phase of overtraining. Hence, what study exercise-induced injury/recovery mechanisms is a critical point to investigate overtraining mechanisms. Recent studies have shown that chronic exercise has been associated peripheral mechanisms stress response, characterized by the rapid transcriptional induction of stress protein (heat shock protein 72, Hsp72) in skeletal muscle, and chronic exercise and heavy endurance training that results in overreaching or overtraining has been related to central mechanisms stress response, characterized by altered stress hormonal (testosterone, cortisol, et al). However, few studies have examined the change of Hsp72 expression to high-intensity and high-volume training that results in overreaching or overtraining, and relation between the change of Hsp72 expression and altered stress hormonal. This study was aimed at investigating whether overtraining modulates Hsp72 expression, and the change of Hsp72 expression may result in alteration to stress hormonal. Finally, Hsp72 expression alteration could provide a new causative theory for overtraining.Methods: Forty-two Sprague-Dauley male rats (2months) were assigned to either a sedentary control group(N=6 per group,3group) or an exhaustively swimming exercise trained group(N=8 per group, 3group).Exercised rats swim 30min-2h for lth-wk(week) and 2th-wk(6d/wk), and exhaustively swim for 3th-wk to 8th-wk(6d/wk). Separately in 6th-wk, 7th-wk, 8th-wk, blood samples collected to determined hemoglobin(Hb) concentration, concentration of serum creatine kinase (CK), serum testosterone(ST), serum cortisol(SCort); the soleus(SOL), the red gastrocnemius muscle(RG), the white gastrocnemius muscle(WG) were excised to determined the relative levels of Hsp72. Results:1 The change of additional overtraining markersFour-six week exhaustively swimming training resulted in overtraining in all exercised rats identified by a significant decline in performance and a significantly reduced Hb, ST, SCort levels and a significantly increased CK levels.2 The change of Hsp72 levelsCompared with sedentary control groups(100%), trained groups in 6th-wk, 7th-wk, 8th-wk, Hsp72 levels in the soleus had respectively decreased 2.6%, 6.6%, 5.3%; Hsp72 levels in the red gastronemius had significantly increased (P < 0.05)(133%, 214%, 157% respectively); Hsp72 levels in the white gastronemius had significantly increased (P < 0.001)(410%, 790%, 1030% respectively). Purely increased Hsp72 of three kinds muscle fibers levels in maximum production was in 6th-wk, followed by a downregulated Hsp72 levels in 6th-wk and 7th-wk, and the change of Hsp72 levels was prior to the stress hormonal.Conclusion : These findings reveal that prolonged strenuous exercise-induced decreased Hsp72 levels was prior to overtraining syndrome.The change of stress hormonal lagged the altered Hsp72 levels, and decreased Hsp72 levels may result in altered stress hormonal levels. Altered Hsp72 levels may be associated peripheral mechanisms of overtraining.