Fig 1.
PRISMA 2009 flow diagram for the literature selection process.
Table 1.
Summary of included randomized controlled studies in athletes.
Fig 2.
Forest plot displaying the effect of vitamin D supplementation on muscle strength and power.
(a) Effect of vitamin D supplementation on upper and lower limb muscle strength. (b) Effect of vitamin D supplementation on muscle power. SMD: standardized mean differences. 95% CI: 95% confidence interval. I2: I-squared test of heterogeneity. Bench press1 / Leg press 1: oral vitamin D3 20000 IU/week for 12 weeks. Bench press 2/ Leg press 2: oral vitamin D3 40000 IU/week for 12 weeks. ICQ: isokinetic concentric quadriceps peak torque. ICH: isokinetic concentric hamstring peak torque. Vertical jump1: oral vitamin D3 20000 IU/week for 12 weeks. Vertical jump2: oral vitamin D3 40000 IU/week for 12 weeks.
Table 2.
Regression analysis of heterogeneity factors for upper limb muscle strength.
Table 3.
Subgroup analysis of muscle strength based on participants’ characteristics.