Figure 2. Eccentric exercise induces hyperalgesic priming.

Seven days after eccentric exercise, following recovery of nociceptive threshold to pre-exercise baseline, PGE₂ (1 μg) was injected into both the ipsilateral and contralateral gastrocnemius muscle. In non-exercised contralateral limbs (filled circles) PGE₂-induced hyperalgesia had completely resolved within 4 h, while in the exercised limbs (filled squares), hyperalgesia was greatly prolonged, being undiminished 240 h after PGE₂ administration.