Physical activity CVD (4+5)

• How does exercise act as a medicine?

  1. Treat exercise as medicine

  Reduces disease through:

  • Neurological - lowers anxiety, depression, risk of stroke, increases cognitive function
  • Cardiovascular - lowers mortality, coronary artery disease, B.P
  • Endocrine - lowers weight, diabetes, LDL, increases HDL
  • Musculoskeletal - decreases osteoporosis, falls, disability
  • Oncological - reduces prostate, breast, bowel cancer
• Whats optimal 'dose' of exercise?

  One size fits all for exercise as a medication, unlike drugs, which are tailored to individuals depending on age, ethnicity

  • Type, intensity, duration, frequency of exercise changes effectiveness of exercise.
• Cross-sectional vs RCT

  Larger number of RCT (gold standard) needed to support findings of epidemiological data.
• Self-report vs objective measures

  Need to be careful with self-report data, there's significant bias with this

  • Resulting in overestimated amount of physical activity.
• What does Exercise, physical activity and cardio-vascular fitness mean?

  • Exercise: Structured
  • Physical activity: Gym, cycling, more broader term e.g walking to the shops
  • Cardio-vascular fitness: Up to 50% is genetically determined
• Higher levels of PA


  Lower risk of CVD
• What are the benefits of PA?

  Can be used as prevention and treatment of CVD
• What are the cardiovascular benefits from PA/exercise?

  • Blood pressure control
  • Improves the blood lipid profile
  • Insulin sensitivity
  • Through promotion of a favourable cardiac risk profile, PA/exercise is associated with a significant reduction in cardiac events
• Among patients with established CAD, there is evidence that exercise reduces the disease process and is the cornerstone of cardiac rehabilitation
• Study looked at heart attacks of London bus drivers (sat around) + ticket collectors (stood up + walking around)


  • Drivers had a higher risk of heart attack compared to conductors
• What is Primary & Secondary Prevention of CVD

  Strong evidence to indicate that PA/exercise protects against the risk of cardiovascular disease:

  • Dose dependent

  Positive impact on cardiovascular risk factors:

  • Hypertension
  • Dyslipidemia
  • T2D
  • NAFLD
• Exercise-based cardiac rehabilitation is considered to be an integral component of rehabilitation in patients with coronary heart disease and heart failure

  
• Cardiovascular fitness vs PA


  High level of PA = lower risk of CVD - even if you have high GENETIC risk of CVD, Those with high genetic risk had the biggest benefit from PA
• Found no scientific evidence for 10,000 steps being beneficial, benefits found at lower amount of steps
• Meta analysis of 15 studies: N = 47,471; 3,013 deaths; 7.1yr follow-up

  FOUND: Taking more steps per day was associated with progressively lower mortality risk

  
  

  Risk reduction plateaued at:

  • Approximately 8000 - 10 000 steps per day for younger adults (aged <60 years)
  • Approximately 6000–8000 steps per day for older adults (aged ≥60 years)

  
• Benefits of going from low PA to higher PA?

  More benefit, with a lower HR

  Greatest benefits are found when those who aren't very active → more active = greatest benefit/biggest change in health
• Sedentary time and physical (in)activity

  Independent risk factors for CVD

  • 'Active coach potato'
  • High levels of sedentary time associated with increased CVD risk and all-cause mortality - even if you do the recommended amount of exercise (its independent)
• Can 45mins of exercise outweigh 12hrs sitting in the office - apparently not, Sedentary time and PA are independent of each other
• Physical activity paradox- occupational vs Leisure-time Activity


  Cross-sectional data suggests opposing effects of occupational physical activity and leisure-time physical activity

  High occupational physical activity (manual labour jobs) associated with increased cardiovascular disease and dementia risk, and all-cause mortality
• Potential reasons for negatives of occupation PA

  • Socioeconomic, racial/ethnic, educational (different levels) confounding factors
  • Shift patterns - cause + effect? - night shifts are related to CVD
  • Repetitive tasks involving prolonged exertion
  • Low levels of control/cognitive stimuli
  • Stress
• PA

  Enhance cardiac and vascular function, structure and reactivity - promotes better O2 use, Reduction in 'traditional' risk factors- systemic effects - blood pressure

  • Reduction in ‘traditional’ risk factors- systemic effects – blood pressure.
• Atheroma Formation


  PA role in reduction of atheroma formation, Smoking increases permeability of endothelium lining = more lipoproteins crossing over = atheroma, PA said to be able to change this
• Atherosclerosis Development


  Lipid plaques form on the inside walls of arteries - specific type of atherosclerosis, Lipid plaques causes arteries to become narrowed + hardened, LDL usually used in normal cell processes, Hypertension, smoking, hyperglycemia (high blood sugar), hypercholesterolemia can cause atherosclerosis, Diapedesis can happen, When WBL + LDL come in contact LDL becomes oxidized, Foam cell is saturated by oxidized LDL, they die + release their contents, engulfed by WBC, Lipids + dead cells are accumulated = plaque, endothelium covers the plaque, which builds in arterial wall

  
• Effects of modest/small changes in diameter of arteries in early atherosclerosis


  Modest but progressive - can effect blood flow, Turbulent flow requires 'more work' to move the column of blood, axial flow is disrupted and resistance to flow in the circulation increases = increased force to continue blood flow, Greater degrees of artery occlusion decreases both oxygen and substrate deliver downstream of the atheroma as flow decreases (eg. 40% decrease in flow decreases peak delivery of O2 and glucose 40%)
• Blood pressure


  A composite (combination) - cardiac output + elasticity + arteriole diameter, Cardiovascular disease can affect ALL of these components, Arteriole diameter is THE MOST IMPORTANT factor in blood flow

  
• Blood Flow

  Proportional to: Pressure difference (P1-P2), Density, Length

  • Changing diameter in critically important to controlling flow in a blood vessel
  • This can ONLY be done at arteries/arterioles (controlling flow into tissues)

  
• Mr DeMarathon – real life example


  • Case Study of Clarence DeMar (Currens and White, 1961) – died of cancer, Prolific marathon runner who competed throughout his adult life, Seven-time winner of the Boston marathon, Last marathon aged 65yrs, Autopsy of his coronary arteries revealed that they were 2 – 3 times the normal diameter of inactive people, No impairment of blood supply despite some atherosclerosis
• Regular exercise

  Promotes arterial remodelling and increased lumen diameter, Arteriogenesis: enlargement of existing arterial vessels

  Exercise training in general increases the luminal diameter and reduces wall thickness of conduit arteries

  Even when atherosclerosis is present, the presence of a marked luminal reserve reduces the probability of flow-limiting stenosis
• Study found femoral artery diameter increased after training men compared to sedentary men


  • Femoral artery diameter of sedentary men before and after training, found the diameter increased
  • Shows artery diameter increases due to regular exercise, can help with reduced risk of CVD due to reduced resistance flow + lower b.p.

  
• Consistent evidence has shown that regular exercise training increases diameter of arteries
• Atherosclerotic plaque


  High CRF (cardiovascular fitness) is associated with higher fibrous volume and/or cap thickness of coronary plaques = less risk of rupture + thrombosis, Regular exercise decreases both the necrotic core area and plaque burden, Benign plaque composition i.e. fewer mixed plaques and more calcified-only plaques

  - Less likely to cause downstream blockages (thrombosis).

  
• Artery stiffening


  Widely believed to be the primary driver of isolated systolic hypertension and is recognised as a major cardiovascular risk factor, Regular aerobic exercise has been shown to attenuate or even reverse stiffening
• Mechanisms that contribute to improved artery compliance

  
  

  Including mechanical, metabolic, neuro-hormonal and anti-inflammatory processes:

  • Higher elastin and lower collagen
  • Increased endothelial shear stress
  • Enhanced NO bioavailability by increasing the expression and activation of endothelial nitric oxide synthase

  
• Exercise intensity


  More effective than volume of exercise, Exercising with higher intensity might result in augmented (larger) release of NO because of greater shear stress on the vascular endothelium
• Study on artery compliance


  • Larger effects observed in participants with greater arterial stiffness at baseline (those in worse shape) and in trials with longer duration, Intensity rather than volume of exercise (frequency and duration of sessions) was positively associated with improvement, Resistance and combined (aerobic and resistance) exercise interventions produced no beneficial effects on PWV or Aix
• Increased plasma cholesterol


  One of the most important risk factors for CVD, Epidemiology has shown a very strong relationship with total cholesterol and CHD mortality independent of other risk factors, Causal relationship is proven by the fact that intervention studies showing reduction of total and LDL cholesterol demonstrate a significant reduction in CHD mortality
• NHS: Healthy adults - Total cholesterol: 5mmol/l or lower

  • Average in the UK: 5.5mmol/l (men) and 5.6 mmol/l (women)
• Resistance and combined (aerobic and resistance) exercise interventions


  • Produced no beneficial effects on PWV or Aix
• Resistance wasn't as effective as aerobic exercise
• Plasma cholesterol


  One of the most important risk factors for CVD