Positive effects of total recovery period on anti- and pro-inflammatory cytokines are not linked to performance re-establishment in overtrained mice

The association between excessive training sessions (i.e., overtraining/OT) and periods of inadequate recovery is linked to the nonfunctional overreaching (NFOR) state, which is defined as an unexplained decrement or stagnation of performance. The cytokine hypothesis of OT considers that pro-inflammatory cytokines are responsible by the NFOR state-induced performance decrement. Investigations using rodent models of OT verified increased levels of pro-inflammatory cytokines in hypothalamus, liver, serum and skeletal muscle samples. Recently, our research group observed that a 2-week total recovery period was not able to re-establish the NFOR state-induced performance decrement. As the responses of anti- and pro-inflammatory cytokines were not measured, we aimed to investigate the effects of 2-week total recovery period on the protein contents of IL-1beta, IL-6, IL-10, IL-15, TNF-alpha and SOCS-3 in serum and skeletal muscle samples of overtrained mice. Also, a bioinformatics analysis was performed to investigate the correlations of IL-1beta, IL-6, IL-10, IL-15, TNF-alpha and SOCS-3 in skeletal muscle with locomotor activity. In summary, the 2-week total recovery period upregulated the anti-inflammatory cytokines and normalized the pro-inflammatory cytokines without a concomitant re-establishment of performance.