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  1. Yu-Wen Chen, PhD*,,
  2. Min-Fei Lin, MS,
  3. Yu-Chung Chen, MS§,
  4. Ching-Hsia Hung, PhD,
  5. Jann-Inn Tzeng, MD, MS,# and
  6. Jhi-Joung Wang, MD, PhD
  1. *Department of Physical Therapy, China Medical University, Taichung; †Department of Medical Research, Chi-Mei Medical Center; and ‡Institute & Department of Physical Therapy, National Cheng Kung University, Tainan; §Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, Cheng Hsin General Hospital, Taipei; and ∥Department of Food Sciences and Technology, Chia Nan University of Pharmacy and Sciences, Jen-Te; and #Department of Anesthesiology, Chi-Mei Medical Center, Yong Kang, Tainan City, Taiwan.
  1. Address correspondence to: Ching-Hsia Hung, PhD, Department of Physical Therapy, National Cheng Kung University, No. 1 Ta-Hsueh Rd, Tainan, Taiwan (e-mail: chhung{at}; CHUNG4@PARTNERS.ORG).


Background Exercise creates a variety of psychophysical effects, including altered pain perception. We investigated whether physical exercise reduces postincisional pain and cytokine and N-methyl-D-aspartate receptor 1 (NR1) expression in a rat model of skin/muscle incision and retraction (SMIR)–evoked pain.

Methods Male Sprague-Dawley rats were divided randomly into 4 groups: sham operated, SMIR-sedentary (SS), SMIR-exercise, and sham operated–exercise. On postoperative day 8, trained rats started to run on a treadmill 55 min/d with an intensity of 18 meter/minute (m/min), 5 days per week for 4 weeks. NR1, tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) expressions in the spinal cord as well as mechanical hypersensitivity following SMIR surgery were assessed for 6 to 35 days.

Results On postoperative day 6, SMIR-sedentary rats exhibited a marked hypersensitivity to von Frey stimuli. By contrast, SMIR-operated rats undergoing exercise demonstrated a quick recovery of mechanical hypersensitivity. The levels of TNF-α, IL-6, and NR1 in the spinal cord were significantly increased in SS rats when compared with sham-operated rats on postoperative days 6, 21, and 35 after SMIR surgery. After the 4-week exercise intervention, the SMIR-exercise group showed lower NR1, TNF-α, and IL-6 expression in the spinal cord than those in the SS group.

Conclusions These results suggest that exercise training decreases persistent postsurgical pain caused by SMIR surgery. There appears to be a protective effect, probably relating to the decrease of NR1, TNF-α, and IL-6 expression in the spinal cord of SMIR rats, after exercise intervention.

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  • The authors report no conflicts of interest.

    This work was done in National Cheng Kung University, Tainan, Taiwan.

    M.-F.L. and J-I.T. contributed equally to this work.

    Financial support was provided by National Science Council, Taiwan (grants NSC 100-2314-B-039-017-MY3 and NSC 101-2815-C-039-019-B).