Studies about vitamin D and injury recovery:
Vitamin D Sufficiency Associates with an Increase in Anti-Inflammatory Cytokines After Intense Exercise in Humans (2014)
Conclusion: A study of young adult males found that those with higher vitamin D levels experienced less muscular inflammation post-exercise compared to those with lower vitamin D levels.
Higher Serum 25-Hydroxyvitamin D Concentrations Associate with a Faster Recovery of Skeletal Muscle Strength After Muscular Injury (2013)
Conclusion: A study of 14 physically active adults found that those with higher vitamin D levels experienced less muscular weakness following intense physical exercise, both immediately and days after the exercise.
Vitamin D Increases Cellular Turnover and Functionally Restores the Skeletal Muscle After Crush Injury in Rats (2013)
Conclusion: In a study where male rats were given crush injuries, those given a giant dose of vitamin D recovered faster.
Note: This is an extensive scholarly article covering the antimicrobial and wound-healing effects of ultraviolet radiation, including as a treatment for antibiotic-resistant pathogens.