The Effects of Vitamin D Supplementation on Aerobic Fitness in Athletes

University of Ulster44 enrolled

Overview

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.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

TRIPLE

Enrollment

Conditions

Aerobic Fitness (VO2max)

Interventions

Vitamin DDIETARY_SUPPLEMENT

3000IU (75 μg) vitamin D in a commercially available oral spray solution

PlaceboDIETARY_SUPPLEMENT

Placebo oral spray solution manufactured to mimic the vitamin D oral spray

Eligibility

Sex: ALLMin age: 18 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Athletes whose sport does not primarily consist of an anaerobic component * Apparently healthy * Over the age of 18 Exclusion Criteria: * Resting arterial hypertension * Individuals who are not an athlete at a University/local sports team * Athletes who predominantly utilise anaerobic energy systems * Athletes under the age of 18 * Those that have consumed a supplement containing vitamin D (greater than 400IU/day) or iron supplements for up to 30 days prior to starting the study * Those with health conditions identified by the screening questionnaire * Individuals that are on prescribed medication that is known to affect vitamin D metabolism * Those following a vegan diet * Those with a physical disability that would prevent successful completion of the exercise test * Those who have either had a sun holiday in the 4 weeks prior to starting the study * Those planning a sun holiday during the intervention period

Locations (1)

Human Intervention Studies Unit (HISU), University of Ulster

Coleraine, Londonderry, United Kingdom

Outcomes

Primary Outcomes

Aerobic fitness (VO2max)

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.

Time frame: At baseline and at 12-weeks

Secondary Outcomes

Hand grip strength

Hand grip dynamometry will be used to assess athletes grip strength. This will be measured on both dominant and non-dominant hands three times. The athlete will be asked to hold the device and grip as tightly as possible whilst holding the device alongside their body. There will be a 10 second rest period between measurements.

Time frame: At baseline and at 12-weeks

Vertical jump height

Athletes will be asked to reach upwards as far as possible, from a standing position and mark this point on a wall. After this they will be asked to perform a counter-movement jump a total of 3 times with a 10 second rest-period between jumps, reaching as high as possible and making a mark each time. Vertical jump height is calculated from the difference between standing reach height and the best height reached when performing a counter-movement jump.

Time frame: At baseline and at 12-weeks

Lung function

Forced expiratory volume at 1 second (FEV1) and forced vital capacity (FVC) will be measured. A calibrated Carefusion® MicroLab portable spirometer will be used to measure these variables.The athletes will need to take a maximal inhalation and then perform a full exhalation as fast as possible into a disposable mouthpiece. This procedure will be repeated three times and an average taken at each time-point. The timing of repeats will be at the athletes discretion.

Data from ClinicalTrials.gov

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