The Effect of an Acute Bout of Exercise on Serum Vitamin D Concentration
Condition: Vitamin D; Acute Exercise
Study type: Observational

Summary: 
      Vitamin D deficiency is considered a public health priority in the UK, with approximately
      30-40% of the UK population being deemed vitamin D deficient during winter months. Current
      government strategies to improve vitamin D status amongst the UK population involve dietary
      supplementation, however, it has been shown that excess adiposity reduces the impact of
      dietary supplementation with vitamin D. One potential explanation for this observation is
      that vitamin D becomes sequestered in adipose tissue. We hypothesise that exercise may
      facilitate the mobilisation of vitamin D from adipose tissue and thus increase circulating
      vitamin D (25OHD) concentrations. Little is currently known as to whether a single bout of
      exercise affects vitamin D status, with a handful of studies demonstrating contradictory
      findings. This research will examine the effect of an acute bout of exercise (treadmill-based
      at 60% VO2 Max for 60 minutes) on vitamin D status (serum 25(OH)D) in healthy
      community-dwelling adults.
    

Detailed description: 
      This study is a random crossover design and will require 34 participants to visit the
      University of Bath on 6 separate occasions in total.

      Individuals who express an interest in taking part will be invited to attend an initial
      screening meeting at the University so that the eligibility can be assessed for the study,
      and the all procedures explained verbally. If the participant is eligible and is happy to
      participate in the study, they will attend a second visit prior to two trials to undertake a
      treadmill-based maximal exercise test (VO2 Max), resting metabolic rate measure and several
      measures will be taken to assess body composition. Trials will involve a 60-minute exercise
      bout at 60% of the participant's maximum oxygen uptake or a 60-minute resting period (both
      followed by a further hour of rest). The order in which these trials occur will be randomised
      for each participant and the participant will not be told of this order prior to the trials.

      During both trials, a cannula will be inserted into a vein in the arm prior to exercise and
      10ml blood samples will be drawn at baseline (pre-exercise) and immediately after the
      exercise session and 1 hour post exercise from the antecubital vein. The participant will
      return to the university the day after each trial for a 10ml venous blood sample (24hr
      post-exercise) which will be taken via venepuncture. In the 24 hours following a trial,
      participants will be provided with standardised meals in order to ensure energy balance.
      Other controls which will be applied during the study period will include the provision of
      factor 50 sunscreen (if the participant is undertaking trials between March and October) to
      aid in mitigating against the cutaneous synthesis of vitamin D, and guidance on avoiding any
      strenuous activity 24 hours prior to trial days. Participants will also be provided with a
      physical activity monitor (MotionWatch8, CamNTech) to wear during trial days after leaving
      the lab.
    

Intervention name(s): Treadmill-Based Exercise (60% VO2 Max for 60 minutes); Rest (60 minutes)
Intervention type(s): Other; Other
Intervention description(s): Each participant will undergo a single 60-minute treadmill-based exercise intervention in a randomised order.
Treadmill settings are generated based on settings which correspond to participants exercising at 60% VO2 max from their maximal exercise test on visit 2. To confirm that participants are exercising at 60% during the hour session, 1 minute samples of expired air are taken at 15 minute intervals and immediately analysed to check % VO2 max. Participants heart rate and RPE measures are also taken at 15 minute intervals throughout the exercise session and cross-checked against predicted values at 60% VO2 Max.; Each participant will undergo a 60-minute rest period in a randomised order.
Observational model: Other
Time perspective: Other
Sampling method: Non-Probability Sample
Study population: 
        Healthy, community-dwelling adults (aged 25-65 years old)
      
Biospecimen description: 
      Human Plasma and Serum
    
Keywords: Vitamin D; Acute Exercise; Adults; United Kingdom; Lipid Mobilisation