Vitamin D in relation to bone health and muscle function in young female soccer players

Abstract

The present work investigated serum vitamin D (25(OH)D) status in relation to bone and muscle qualities and functions in 19 female soccer players (13–16 years) resident at northern latitude with very low sun exposure (∼32–36 h/month) during winter season (late January to early March). Serum 25(OH)D, parathyroid hormone and bone turnover markers osteocalcin (OC) and beta carboxy-terminal collagen cross-links (β-Ctx), as well as body composition and muscle performance were examined. Hormones were tested using routine laboratory methods. Fat mass, lean mass, and bone mineral density in whole body, as well as femur and lumbar spine were evaluated with dual-energy X-ray absorptiometry. Muscle performance was assessed through isokinetic knee extension and flexion, countermovement jump, and sprint running. 25(OH)D was low (50.5 ± 12.8 nmol l⁻¹), whereas the values of bone turnover markers were markedly high (OC: 59.4 ± 18.6 µg l⁻¹; β-Ctx: 1075 ± 408 ng l⁻¹). All bone and muscle measurements were normal or above normal. 25(OH)D was not significantly correlated with most of the parameters of bone and muscle quality or function, except the knee extension time to peak torque (r  = −0.50, p = .03). In conclusion, the level of vitamin D is markedly low in adolescent female soccer players during the winter in Sweden. However, vitamin D levels did not significantly correlate with measures of bone and muscle except a moderate correlation in time to peak torque in the knee extensors. The practical implication of low vitamin D levels in young growing female athletes remains unclear.

Keywords:

• Exercise
• education
• health
• kinesiology
• fitness

Acknowledgements

The authors would like to thank Roger Andersson at the Sport sciences lab, Umeå University and postgraduate students Joel Lindström and Erik Blombäck for assistance during testing. The authors would also like to thank Jonas Johansson for valuable comments on the manuscript, and all the test subjects for participating in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCiD

André Brännström http://orcid.org/0000-0003-4624-1881

Jiguo Yu http://orcid.org/0000-0003-1251-348X

Per Jonsson http://orcid.org/0000-0003-1597-5372

Torbjörn Åkerfeldt http://orcid.org/0000-0003-0214-596X

Mats Stridsberg http://orcid.org/0000-0002-9198-4193

Michael Svensson http://orcid.org/0000-0003-4972-4416

Additional information

Funding

This work was supported by the Umeå School of Sport Sciences, Umeå University.