Effects of Resistance Training Combined with Vitamin D Supplementation on Health-Related Variables in the Elderly: Muscle Strength, Body Composition, and Inflammatory Status

Aging is associated with changes in body composition that lead to low-grade chronic inflammation, compromising the health of the elderly. This condition can be mitigated by resistance training (RT) and vitamin D supplementation, promoting the health of this population. This study aimed to investigate the effects of 12 weeks of RT combined with vitamin D supplementation on body composition, muscle strength, and inflammatory status in older adults. A total of 26 participants were randomly assigned to an Experimental Group (EG: n = 12; 11 Female; 70.6 ± 4.7 years; RT + 2000 IU/day of vitamin D) and a Control Group (EG: n = 14; 11 Female; 69.6 ± 4.6 years; RT + placebo). Both groups performed the same RT program (8 exercises; 2 sets; 10 RM, twice per week). Before and after the intervention, participants were assessed using DEXA, strength tests (sit-to-stand test and handgrip strength), and serum biomarkers (IL-6, TNF-α, 25(OH)D). Both groups showed significant strength gains, particularly in the lower limbs (<i>p</i> < 0.05 for all tests and groups), with no between-group differences in body composition or inflammatory markers (<i>p</i> > 0.05 for all tests and groups). A time × group interaction was observed for IL-6 (<i>p</i> = 0.03), with a slight reduction in the EG and an increase in the CG, although post-intervention differences were not statistically significant (<i>p</i> = 0.49). No statistically significant between-group difference in 25(OH)D change (<i>p</i> = 0.11). These findings suggest that vitamin D supplementation at the tested dose did not enhance adaptations to resistance training in older adults with normal baseline vitamin D levels. Further studies are warranted to explore potential benefits in deficient populations and with alternative dosing strategies.