830 nm Pretreatment in Mice Enhances Endurance in Acute Exercise

Fatigue is defined by the reduction of a muscle's strength and performance during exercise and continuous activity will result in musculoskeletal injury. 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. Photobiomodulation therapy (PBMT) reduces pain, inflammation and enhances physical performance. However, the mechanism(s) of cellular responses by PBM in muscle is not clearly understood. Therefore, the goal of this study is to improve our understanding of the mechanism(s) of action of PBM effects on the musculoskeletal system, in exercised and healthy muscle. We investigate the application of 830 nm and its effect on sedentary muscle and fatigue induced in intense exercise in mice. In sedentary mice, PBM increased the gene expression for muscle tissue development, including cFos, which is critical for activating satellite cells that repair muscle. Immunostaining for cFos expression confirmed an increase in number of activated satellite cells in PBM treated muscle. We performed a treadmill fatigue assay and collected muscle tissue for histological and biochemical analysis. We observed that PBM treated mice had increased performance, reduced muscle fiber damage and altered mitochondrial structure. RNA sequencing from fatigued TA suggested that PBM treatment had increased gene expression of tissue regeneration and remodeling, suggesting tissue adaptation and muscle repair after exercise with PBM. In conclusion, our study suggests that 830 nm may have altered the muscle by activating regenerative genes that protect the tissue from exercise induced cellular stress. Overall design: We performed Differential Gene Expression analysis from the RNA-seq data of 12 sedentary (6 non-PBM and 6 PBM treated) and 12 fatigue (6 non-PBM and 6 PBM treated) male mice.