Resistance exercise can increase the number of Vitamin D receptors (VDRs) in the muscle and improve Vitamin D metabolism, according to a study published in Experimental Physiology.
Vitamin D is synthesised in the skin through UV radiation or consumed through diets. It has many physiological and biochemical functions in the body, especially in calcium and bone metabolism. Vitamin D deficiency is associated with muscle atrophy, reduced muscular strength and consequent increased risk of recurrent falls and fractures in the elderly.
Previous research has shown that Vitamin D supplementation increases the number of VDRs and improves muscle mass and function in people with vitamin D deficiency. Resistance exercise is well known to enhance muscle growth and improve muscle function, but the effect of resistance exercise itself on VDRs has not been previously investigated. In the current study, the scientists demonstrated for the first time that an acute bout of resistance exercise, but not aerobic exercise, can increase the intramuscular expression of VDRs.
The researchers subjected 10 week-old male rats to either resistance exercise (by electrical stimulation) or endurance exercise (treadmill run). Muscle samples were taken at rest and after a bout of exercise to compare the changes in VDRs and proteins related to Vitamin D metabolism.
Dr Satoshi Fujita, from Ritsumeikan University, Japan, and lead investigator of the study said,
'This is an important finding. Since resistance exercise, but not aerobic exercise, can increase VDRs, resistance exercise could be an efficient way to improve Vitamin D metabolism without supplementation. Furthermore, our results suggest that the mechanisms over exercise-induce increased VDR expression might be different to the ones induced by vitamin supplements.'
He added, 'For future research, the contribution of Vitamin D in exercise-induced muscle protein anabolism needs to be investigated to see whether resistance training combined with Vitamin D supplementation can stimulate muscle protein anabolism more than exercise alone'.