There is a high prevalence of vitamin D deficiency in Switzerland. In indoor-athletes as well as wheelchair users, vitamin D deficiency occurs even more often. It is well established that vitamin D deficiency has a negative effect on health. However, vitamin D supplementation in individuals with a vitamin D deficiency has a positive effect on muscle performance. In recently published studies with able-bodied subjects, it has been shown that a normal vitamin D level (>75nmol/L) can only be achieved with a high-dose supplementation of vitamin D.

The aim of this study is to examine the effect of vitamin D supplementation on exercise performance in wheelchair athletes with vitamin D deficiency . All participants with a vitamin D deficiency are assigned to the intervention group and treated with 6000 IU of vitamin D3 daily over a period of 12 weeks. All participants who have a normal vitamin D level will receive placebo treatment (control group). The physical performance is measured three times at baseline, after six weeks and 12 weeks. The measurements include a Wingate and a dynamometer test.

Inclusion Criteria:

• swiss elite wheelchair athlete
• 18 to 60 years
• male, healthy
• at least 2x45min sports a week

Exclusion Criteria:

• participation in another study
• medication which influences performance
• respiratory and cardiovascular disease
• daily intake of >400IU Vitamin D
• parathyroid gland disease
• kidney insufficiency
• visit abroad below the 37th parallel latitude during study or shortly before