Pretreatment With 830nm Prevents Muscular Fatigue in Intense Exercise in Mice- MHSRS 2024

cheema n, ghag n, wise e, pham l, nazarian a, fuchs c, tam j, anderson r

Abstract accepted for poster presentation at the 2024 Military Health System Research Symposium

Fatigue is defined by the reduction of a muscle’s strength and performance during exercise, and it is affected by different parts of the motor pathway controlling muscle contractions. Fatigue limits performance and unless allowed to recover, continuous activity will result in musculoskeletal injuries that are commonly observed in military personnel. Light therapy has been shown to have several beneficial physiologic effects in a wide range of tissues. The musculoskeletal system can be irradiated with wavelengths in red and near infrared (NIR) regions which penetrate deep into the body. Recent studies are suggesting that photobiomodulation therapy (PBMT) can reduce pain, inflammation and enhance physical performance. However, the mechanism(s) of cellular responses by PBM in muscle is not clearly understood. There is no standardization in parameters for PBMT, with researchers and clinicians using a wide range of wavelengths, fluences, etc. Therefore, the goal of this study is to improve our understanding of the mechanism(s) of action of PBM effects on the musculoskeletal system, ultimately to inform the choice of clinical treatment parameters. We investigate the application of 830 nm and its effect on fatigue induced in intense exercise in mice. We performed a treadmill fatigue assay on mice and collected muscle tissue for histological and biochemical analysis. We observed that PBMT mice ran twice as long. Electron microscopy of fatigued muscle had some evidence of cellular stress where mitochondrial structure is altered whereas 830 nm treated muscle had a preservation of mitochondrial morphology. RNAseq data from fatigue muscle suggests that treated mice have an upregulation of genes involved in tissue remodeling, specifically cytoskeletal and vasculature markers. During muscle regeneration, mechanoreceptors, known as muscle spindle fibers form after innervation by the motor neuron. We saw increased number of muscle spindle fibers, which stimulate muscle contraction in response to stretch. Other signs of muscle regeneration, also observed in our treated muscle, are myoblast fusion and central localization of the myonucleus. In conclusion, our study suggests that 830 nm may have altered the muscle by activating regenerative genes that protect the muscle from cellular stress from intense exercise.