title: Acute Effects of Vitamin D3 Supplementation on Muscle Strength in Judoka Athletes: A Randomized Placebo-Controlled, Double-Blind Trial.
abstract: OBJECTIVE
  Indoor athletes have been shown to be prone to vitamin D3 deficiency. The aim of the study was to examine the acute effects of vitamin D supplementation on muscle function using isokinetic dynamometry.
  
  
  METHODS
  Randomized placebo-controlled, double-blind study.
  
  
  METHODS
  Institutional.
  
  
  METHODS
  Adult male white national level judoka athletes (n = 22) who were involved in full-time training. Exclusion criteria were vitamin supplementation, overseas travel to sunny climes, and/or an injury incurred during the last 3 months before testing.
  
  
  METHODS
  Subjects were randomly allocated to the treatment (150 000IU vitamin D3) or placebo and given blinded supplements by an independent researcher. Participants were tested twice, 8 days apart, on a Monday morning before the start of judo training and after 2 days of rest. A 5 to 7 mL of blood sample was collected followed by isokinetic concentric quadriceps and hamstring muscle function assessments on the right leg at 30 and 200°·s.
  
  
  METHODS
  Repeated-measures analysis of variance was used to analyze isokinetic muscle force and serum 25(OH)D3. Regression to the mean was used to examine changes in 25(OH)D3 levels over the study period.
  
  
  RESULTS
  The treatment group demonstrated a significant increase in serum 25(OH)D levels (34%, P ≤ 0.001) and muscle strength (13%, P = 0.01) between days 1 and 8. No significant differences were found for the placebo group for the same period.
  
  
  CONCLUSIONS
  A single bolus of 150 000IU vitamin D3 had a significant positive effect on serum 25(OH)D levels and muscle function in vitamin D insufficient elite indoor athletes.
  
  
  CONCLUSIONS
  Serum 25(OH)D3 levels of indoor athletes should be monitored throughout the year and especially during winter months. Beneficial responses, in muscle strength and serum 25(OH)D3, to 1 dose of vitamin D3 supplementation can be observed within 1 week of ingestion. Muscle strength is linked to serum 25(OH)D levels.
authors.affiliation: *Research Centre for Sport Exercise and Performance, University of Wolverhampton, Walsall, United Kingdom; †National Institute of Dance Medicine and Science, United Kingdom; ‡Department of Rheumatology and Sport and Exercise Medicine, Royal National Orthopaedic Hospital, Stanmore, United Kingdom; §Research Centre for Sport Exercise and Performance, University of Wolverhampton, Walsall, United Kingdom; ¶School of Pharmacy, School of Life Sciences, Aston University, Birmingham, United Kingdom; and ‖Department of Exercise Sciences, University of Thessaly, Trikala, Greece.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Wyon
authors.forename: Roger
authors.initials: R
authors.lastname: Wolman
authors.forename: Alan M
authors.initials: AM
authors.lastname: Nevill
authors.forename: Ross
authors.initials: R
authors.lastname: Cloak
authors.forename: George S
authors.initials: GS
authors.lastname: Metsios
authors.forename: Douglas
authors.initials: D
authors.lastname: Gould
authors.forename: Andrew
authors.initials: A
authors.lastname: Ingham
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Koutedakis
mesh_terms: D000328:Adult; D056352:Athletes; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000097:blood; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D008297:Male; D016139:Martial Arts; D053580:Muscle Strength / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D055815:Young Adult
chemical_list: D002762:Cholecalciferol