The influence of combined vitamin D3 supplementation and resistance exercise training on musculoskeletal health in older men and women

Sarcopenia, defined as the loss of muscle mass, strength and function has serious personal and societal implications. This is mainly via the loss of independence and decreased quality of life, and the prevalence of sarcopenia is known to increase with age. Although resistance exercise training is known to combat sarcopenia, improvements observed in older adults are blunted in comparison to younger adults. Some observational and interventional evidence suggest that vitamin D is associated with aspects of sarcopenia, therefore, the aim of this thesis was to determine if vitamin D3 supplementation combined with resistance exercise training was more effective in improving musculoskeletal health than resistance exercise training alone. Chapter 2 presented the first systematic review and meta-analysis of the effect of combined resistance exercise training and vitamin D3 supplementation on musculoskeletal health in older adults. A total of 7 studies including 792 participants were reviewed. A small but significant improvement in muscle strength of the lower limb and further improvements in muscle function parameters and bone mineral density was evidenced as a result of the combined intervention from a subgroup of 3 studies (n = 518) adopting a similar methodology. The review highlighted the lack of studies implementing an appropriate study design (i.e. the combined intervention compared to exercise alone) and sample size to investigate the role of vitamin D in improving aspects of sarcopenia. Chapter 3 presents a secondary data analysis examining the association between seasonal serum 25(OH)D concentration, lean mass and strength and the novel outcome of seasonal-dependent sarcopenic status in a subgroup of postmenopausal women from the Vitamin D, Food Intake, Nutrition and Exposure to Sunlight in Southern England (D-FINES) cohort. No association between lean mass and 25(OH)D concentration was observed, however, muscle strength and serum 25(OH)D concentrations were positively associated across all 4 seasons. Sarcopenic status was found to be transient in a very small sample of sarcopenic participants (n = 10). The Exercise and vitamin D study (EXVITD) is presented in Chapters 4 to 6. This was a 6-month double-blinded, randomized controlled trial of twice weekly resistance exercise training and daily supplemental vitamin D3 (800 IU) or placebo tablet. This study recruited 24 community-dwelling older adults (mean age = 70.83 years), with 19 participants completing the intervention. Between-group differences were not detected in any of the outcome measures assessed, most likely due to the small sample size of recruited participants. The results presented here suggest that further research is warranted and thus, recommendations for future studies are presented in Chapter 7