Abstract
Muscle injury caused by direct trauma to the skeletal muscle is among the main musculoskeletal disorders. Non-pharmacological treatments have been effective in controlling muscle injury–induced pain; however, there are just a few studies in the literature investigating this response. Thus, the present study aimed to evaluate the effect of a resistance exercise training protocol combined or not with whey protein supplementation on mechanical allodynia induced by muscle injury. In addition, we also investigated the involvement of spinal glial cells in this process. For this purpose, male Wistar rats underwent a muscle injury model induced by direct trauma to the gastrocnemius muscle. Mechanical allodynia was measured by a digital von Frey algesimeter test. To evaluate the effect of exercise and/or supplementation on mechanical allodynia, the animals practiced exercises three times a week for 14 days and received supplementation daily for 14 days, respectively. Moreover, the effect of both the participation of spinal glial cells in the muscle injury and the resistance exercise training and/or whey protein supplementation on these cells was also investigated by the Western blot assay. The results demonstrated that resistance exercise training and whey protein supplementation, combined or alone, reduced mechanical allodynia. These treatments also reduced the number of interstitial cells and pro-inflammatory cytokine IL-6 levels in the injured muscle. It was also found that spinal microglia and astrocytes are involved in muscle injury, and that resistance exercise training combined with whey protein supplementation inhibits spinal microglia activation. The results suggest that both resistance exercise training and whey protein supplementation may be effective non-pharmacological treatments to control pain in the muscle after injury induced by acute trauma.
Highlights
Skeletal muscle injuries are common during sports practice and comprise 10–55% of all injuries (Delos et al, 2013)
For the experiments described below, the animals were randomly divided into the following groups (n 5–6): naive, composed of rats not subjected to the muscle injury model; MI, comprising rats subjected to the muscle injury model; MI + RET, formed by rats subjected to the muscle injury model and the resistance exercise training; MI + WP, composed of rats subjected to the muscle injury model and that received whey protein supplementation; and MI + RET + WP, comprising rats subjected to the muscle injury model, followed by resistance exercise training and whey protein supplementation
In some experimental groups, we evaluated the effect of whey protein supplementation vehicle or resistance exercise training in naïve rats by comparing them to rats not subjected to the muscle injury model, and that received whey protein supplementation vehicle; rats subjected to the muscle injury model and that received saline; rats not subjected to the muscle injury model and that received whey protein supplementation; rats not subjected to the muscle injury model and that performed resistance exercise training; and last, rats not subjected to the muscle injury model that received a combination of saline and resistance exercise training
Summary
Skeletal muscle injuries are common during sports practice and comprise 10–55% of all injuries (Delos et al, 2013). These injuries are often accompanied by severe and lasting pain, which can impact the functionality, emotional health, and the quality of life of the affected individuals (Gigante et al, 2014). The muscle injury recovery process depends on relatively wellestablished phases, such as degeneration, inflammation, and regeneration (Laumonier and Menetrey, 2016). Inflammation associated with muscle regeneration is complex since it relies on the balance between pro- and anti-inflammatory factors (Laumonier and Menetrey, 2016). There are classical signs and symptoms, including loss of function, hyperthermia, edema, and erythema (Gibbins, 2018), which may cause discomfort or even pain to the individual
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