Individual Variability of Coronary Heart Disease Risk Markers and Sleep Responses to Exercise
Condition: Coronary Heart Disease; Cardiovascular Risk Factor; Arterial Stiffness; Blood Pressure; Sleep
MeSH terms: Heart Diseases; Coronary Disease; Coronary Artery Disease; Myocardial Ischemia
Study type: Interventional

Summary: 
      The aim of this study is to examine the reproducibility of postprandial coronary heart
      disease (CHD) risk marker and sleep responses to acute exercise bouts and to quantify the
      magnitude of individual variability in responses using a replicated crossover design.
      Healthy, recreationally active men will complete two identical rest control and two identical
      exercise (60 min at 60% maximum oxygen uptake) conditions in randomised sequences. Fasting
      and postprandial venous blood samples, arterial blood pressure and arterial stiffness
      measurements will be taken at pre-determined intervals, and sleep duration and quality will
      be assessed. Reproducibility and individual variability will be examined using bivariate
      correlations and linear mixed modelling.
    

Detailed description: 
      Single bouts of exercise reduce circulating concentrations of postprandial triacylglycerol -
      an established independent risk marker for coronary heart disease (CHD). The exercise-induced
      reduction in postprandial triacylglycerol concentrations has been shown to coincide with
      transient changes in other CHD risk markers, including reductions in postprandial insulin,
      interleukin-6, arterial stiffness and resting arterial blood pressure, and exercise may also
      promote sleep duration and quality. Individual variability in these responses is suspected
      but has not been examined using robust designs and appropriate statistical models. A recent
      approach to quantify individual variability in the intervention response involves quantifying
      the participant-by-condition interaction from replicated intervention and comparator arms.
      Using this approach (the replicated crossover design), the present study will (i) examine
      whether the postprandial CHD risk marker and sleep responses to acute exercise are
      reproducible on repeated occasions; and (ii) determine whether there is true individual
      variability in postprandial CHD risk marker and sleep responses to acute exercise.

      A total of 20 healthy, recreationally active men will be recruited. Participants will
      undertake a preliminary measures visit (visit 1) to confirm eligibility, to undergo
      anthropometric measurements and to determine maximum oxygen uptake. Participants will
      complete four, 2-day experimental conditions in randomised sequences separated by at least
      one week: two identical control and two identical exercise conditions. On day 1 (visits 2, 4,
      6 and 8), participants will arrive fasted at 08:00 and a baseline blood sample, blood
      pressure and arterial stiffness measurement will be taken. Participants will consume a
      standardised high fat breakfast at 08:45 (0 h) and lunch at 12:45 (4 h). A second arterial
      stiffness measurement will be taken at 16:45 (8 h). The two control and two exercise
      conditions will be identical, except that participants will be asked to exercise on the
      treadmill for 60 minutes at 60% of their maximum oxygen uptake at 15:15 (6.5 h) in both
      exercise conditions. On day 2 (visits 3, 5, 7 and 9), participants will arrive fasted at
      08:00 and will rest in the laboratory throughout the day in the two control and two exercise
      conditions. Participants will consume a standardised breakfast at 08:45 (0 h) and a
      standardised lunch at 12:45 (4 h). Venous blood samples will be collected at 0, 0.5, 1, 2, 3,
      4, 4.5, 5, 6, 7 and 8 h. Resting arterial blood pressure will be measured at hourly
      intervals. Arterial stiffness will be measured at 0, 2.5 and 5 h. Sleep duration and quality
      will be assessed for three nights before and two nights after visits 3, 5, 7 and 9 using a
      triaxial actigraphy watch.

      Reproducibility and individual variability will be explored by correlating the two sets of
      response differences between exercise and control conditions. Within-participant
      covariate-adjusted linear mixed models will be used to quantify participant-by-condition
      interactions. It is hypothesised that (i) control-adjusted postprandial CHD risk marker and
      sleep responses to acute exercise will be reproducible; and (ii) true interindividual
      variability will exist in postprandial CHD risk marker and sleep responses to acute exercise
      beyond any random within-subject variation.
    

Intervention name(s): Exercise
Intervention type(s): Behavioral
Intervention description(s): 60 min treadmill exercise performed at 60% of maximum oxygen uptake.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science