Completed
PHASE4
INTERVENTIONAL
NCT02278172
The Effects of Vitamin D Supplementation on Aerobic Fitness in Athletes
View on ClinicalTrials.gov
Updated Dec 15, 2025
Brief Summary
The primary aim of the study is to identify if vitamin D3 supplementation influences VO2max in athletes. Secondary aims are to determine if vitamin D3 supplementation impacts on measures of muscle function, lung function, body composition, immune function and the self-reported incidence of upper respiratory tract infection. This double-blind, randomised, placebo-controlled trial is of parallel design and will aim to recruit a total of 50 athletes randomised into either a placebo or treatment group for a 12-week intervention.
Interventions
Name:
Vitamin D
Type:
DIETARY_SUPPLEMENT
Description:
3000IU (75 μg) vitamin D in a commercially available oral spray solution
Name:
Placebo
Type:
DIETARY_SUPPLEMENT
Description:
Placebo oral spray solution manufactured to mimic the vitamin D oral spray
Primary Outcomes
Measure:
Aerobic fitness (VO2max)
TimeFrame:
At baseline and at 12-weeks
Description:
A medical screening questionnaire will be completed prior to the test. Athletes resting blood pressure will be measured twice to rule out resting hypertension. After a standardised warm-up, starting speed will be 8/km/hr at 1% incline, until 17/km/hr, after which incline will increase by 1% every minute until VO2max is met. A metabolic cart (Metalyzer 3B) will measure the athlete's ventilation (oxygen uptake and carbon dioxide output) throughout the test.
The test will be terminated when two of the following criterion are met\*:
Respiratory exchange ratio reaches/exceeds 1.15 AND VO2 plateau observed OR Heart rate within 10bpm of age-predicted maximum
\* Except when volitional exhaustion occurs Athletes will be asked to refrain from strenuous activity for 24 hours prior to VO2max testing in order to control for last bout effects.
Post-exercise lactate concentration (age and gender adjusted) will further-verify that VO2max was attained using a Lactate Pro device.
Trial Information
NCT ID
NCT02278172
Status
Completed
Study Type
INTERVENTIONAL
Phases
PHASE4
Sponsor
University of Ulster
Last Updated
December 15, 2025