• Mahdi Hosseinzadeh, Afshin Samani, Ole K Andersen, Kazunori Nosaka, Lars Arendt-Nielsen, and Pascal Madeleine.
• Physical Activity and Human Performance Group, SMI, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, 9220, Aalborg, Denmark.
• Eur. J. Appl. Physiol. 2015 Nov 1; 115 (11): 2253-62.

PurposeThis study aimed to investigate the hypothesis that a repeated bout of eccentric exercise (ECC2) would result in smaller increase in the sensitivity of spinal nociceptive system, and smaller decrease in the local muscle blood oxygenation response in both the ipsilateral and the contralateral tibialis anterior muscle (TA) when compared with the initial bout (ECC1). It was hypothesized that the magnitude of the repeated bout effect (RBE) would be greater for the ipsilateral side than the contralateral side.MethodsTwenty-six healthy young men performed two bouts of high-intensity eccentric exercise of TA separated by 2 weeks. Half of the participants used the same leg for both bouts (IPSI) and the other half used the contralateral leg for ECC2 (CONTRA). Nociceptive withdrawal reflex threshold (NWRT) and local muscle blood oxygenation were assessed for the exercised TA muscle before, immediately after, and one day after exercise.ResultsSignificant decreases in NWRT and muscle oxygenation were observed after ECC1 (p < 0.05), but NWRT did not change after ECC2 in both groups. Smaller decreases in muscle oxygenation were observed after ECC2 than ECC1 in both groups with a similar magnitude of the difference between bouts, but an increase in muscle oxygen re-perfusion before ECC2 was only observed in the IPSI group.ConclusionThese results suggest that contralateral RBE was associated with spinal facilitation of the neuronal pathways situated at a homologous innervation level, and it is unlikely that oxygen re-perfusion improvement plays a major role in the contralateral RBE.

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