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Abstract
Inexperienced vigorous exercise, including eccentric contraction (ECC), causes muscle pain and damage. Similar prior light exercise suppresses the development of muscle pain (repeated-bout effect), but the molecular mechanisms behind this are not sufficiently understood. In this study, the influence of a nondamaging preconditioning ECC load (Precon) on muscle pain-related molecules and satellite cell-activating factors was investigated at the mRNA expression level. Nine-week-old male Wistar rats (n=36) were divided into 2 groups: a group receiving only a damaging ECC (100 contractions) load (non-Precon) and a group receiving a nondamaging ECC (10 contractions) load 2 days before receiving the damaging ECC load (Precon). ECC was loaded on the left leg, and the right leg was regarded as the intact control (CTL). The medial head of the gastrocnemius muscle from all rats was excised 2 or 4 days after the damaging ECC loading, and the relative mRNA expression levels of muscle pain- and satellite cell-related molecules were quantitated using real-time RT PCR. Precon suppressed increases in MHC-embryonic and MHC-neonatal mRNA expressions. Enhancement of HGF, Pax7, MyoD, and myogenin mRNA expression was also suppressed, suggesting that Precon decreased the degree of muscle damage and no muscle regeneration or satellite cell activation occurred. Similarly, increases in mRNA expression of muscle pain-related molecules (BKB2 receptor, COX-2, and mPGEC-1) were also suppressed. This study clearly demonstrated that at the mRNA level, prior light ECC suppressed muscle damage induced by later damaging ECC and promoted recovery from muscle pain.
Highlights
Inexperienced vigorous exercise, including eccentric contraction (ECC), induces muscle damage, edema, reduction of tension, limitation of the range of motion, and muscle pain
We confirmed that the maximum isometric torque of the plantar flexor muscles was not reduced 48 hours after 10 repeated ECC. e left muscles in the non-preconditioning ECC load (Precon) group were exposed to damaging ECC without Precon. 0 (Immediately), 2, or 4 days after completion of damaging ECC, the planter flexor muscles were removed from each animal (n 6 in each group). e medial gastrocnemius muscles were used for further analyses
In sections of hematoxylin and eosin (H&E) at 2 and 4 days after damaging ECC, a number of swollen myofibers with rounded shape and many inflammatory cells surrounding them were observed in the non-Precon group (Figures 1(c) and 1(e)), while these unfavorable changes dramatically were suppressed in the Precon group (Figures 1(d) and 1(f ))
Summary
Preconditioning Contractions Suppress Muscle Pain Markers after Damaging Eccentric Contractions. Inexperienced vigorous exercise, including eccentric contraction (ECC), causes muscle pain and damage. The influence of a nondamaging preconditioning ECC load (Precon) on muscle pain-related molecules and satellite cell-activating factors was investigated at the mRNA expression level. E medial head of the gastrocnemius muscle from all rats was excised 2 or 4 days after the damaging ECC loading, and the relative mRNA expression levels of muscle pain- and satellite cell-related molecules were quantitated using real-time RT PCR. Enhancement of HGF, Pax, MyoD, and myogenin mRNA expression was suppressed, suggesting that Precon decreased the degree of muscle damage and no muscle regeneration or satellite cell activation occurred. Is study clearly demonstrated that at the mRNA level, prior light ECC suppressed muscle damage induced by later damaging ECC and promoted recovery from muscle pain Increases in mRNA expression of muscle pain-related molecules (BKB2 receptor, COX-2, and mPGEC-1) were suppressed. is study clearly demonstrated that at the mRNA level, prior light ECC suppressed muscle damage induced by later damaging ECC and promoted recovery from muscle pain
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