What is the definition of health?
“A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” (p 1. W.H.O., 1947)
What did Bouchard et al. (2007) show?
That there is a complex interaction between health, physical activity and physical fitness. There are important determinants from heredity, lifestyle and environment.
Which key studies give evidence of lower mortality in more physically active and / or higher fit people?
• Harvard Alumni Health Study 1986: (Paffenbarger et al., NEJM, 315) + Harvard Alumni Health Study 1995: (Lee et al., JAMA, 273) • Blair et al. 1989: aerobic centre longitudinal study • Framingham study • Baugerleuser study • Zutphen elderly study & Finnish Twin Cohort
What did the Harvard Alumni Health Study 1986: (Paffenbarger et al., NEJM, 315) study show?
Mortality ↓ with ↑ physical activity 27% less risk of mortality from expending >2000kcal per week
What did the Harvard Alumni Health Study 1995: (Lee et al., JAMA, 273) show?
Mortality ↓ with ↑ physical activity (Confirmed the 1986 HAHS results; that less risk of mortality from expending >2000kcal per week)
How would you expend >2000kcal per week?
Walking at 4mph = 400Kcal ph, thus 5hrs walking per week for 2000Kcal
What did the results of the Harvard Alumni Health Studies recommend?
less risk of mortality from expending >2000kcal per week (Walking at 4mph = 400Kcal ph, thus 5hrs walking per week for 2000Kca)
What did the Aerobic centre longitudinal study 1989: (Blair et al., JAMA, 262) show?
1. Biggest drop in mortality moving from lowest fit (Q1) to below average fitness (Q2) 2. Low fit men have 3.3 and low fit women 4.7 X more mortality than high fit (Q5)
The combination of results from the Zutphen elderly study & Finnish Twin Cohort study + British regional heart study, • Harvard Alumni Health Study, aerobic centre longitudinal study and the study of osteoporotic fractures shows what?
That it is never too late for previously inactive patients to become more active as it has been shown to have an impact on their mortality risk ratio. Also that those with the lowest activity/fitness have the most to gain in terms of mortality risk when commencing PA.
What does the ACSM, 2010 evidence show?
A) Occupational and leisure activity: 2 X more CHD death for sedentary vs. active occupations. 2 X more CHD death for low vs. high non- occupational physical activity. B) Fitness Every 1 MET increase in aerobic fitness = 12% more survival Below 5 METs = worse prognosis
Below which MET level do you have a worse prognosis?
Below 5 METs
Increasing your MET by 1 improves your survival by what percentage?
Every 1 MET increase in aerobic fitness = 12% more survival
What is the best recommendation for occupation & leisure activity in terms of CHD death risk?
Active occupation + high PA outside occupation [2 X more CHD death for sedentary vs. active occupations. 2 X more CHD death for low vs. high non- occupational physical activity.]
What are the axis on the dose-response curve?
Y - health benefits X - activity status
What are the consequences of the dose-response curve?
The greatest health benefits are achieved when increasing physical activity levels from sedentary to moderately active + The more physical activity you do, the greater the health benefits -- Each 10 minutes of MVPA results in 10% mortality risk reduction (RR) -- Achieve 150 mins MVPA then 30-40% less RR -- 750 mins MVPA (3 X recs) only increases RR to 50%
What does the dose-response curve tell us about mortality risk reduction (RR)?
-- Each 10 minutes of MVPA results in 10% mortality risk reduction (RR) -- Achieve 150 mins MVPA then 30-40% less RR -- 750 mins MVPA (3 X recs) only increases RR to 50%
Is there truly a steeper relationship between fitness and relative risk than PA? And what are the consequences for public health initiatives?
--Likely due to measurement error in physical activity studies (Easier to objectively measure physical fitness) --Public health initiatives should target physical activity because that will increase fitness levels
What did Clarke et al, BMJ 2012 show about Olympians?
Olympians live 2.8 years longer on average. Thought to be due to genetics, wealth and PA throughout life. Endurance athletes had greatest benefit, but even resistance athletes benefitted.
Should you exercise even if unwell? What is the evidence?
Yes: Physically fit men with existing chronic conditions (e.g., CVD, HTN, DM) have a lower risk of mortality compared with men who are unfit. Hypertension High fit without HTN had 0.5 mortality risk reduction (RR) of low fit High fit with incidental (white coat) HTN had 0.4 RR of low fit High fit with history of HTN had 0.4 RR of low fit Diabetes High fit with DM had 0.5 RR of low fit without DM
For which clinical health conditions is there good evidence to suggest that being active / fit helps prevent or treat?
CHD, stroke, HTN, cancer, diabetes, falls, depression, dyslipidaemia. (2008 physical activity guidelines for Americans: US Dept Health and Human Services)
What are the key new points from the 2008 physical activity guidelines for Americans?
• VPA and MPA can be mixed up. VPA>MPA? • Fq: can spread over week/weekend warriors (but fq bouts better for DM, HTN, depression, hyperlipidaemia etc.) • Duration: 10min bouts currently recommended; but <10min still beneficial as avoids sedentary behaviours
What are the 2008 PA guidelines for American Adults?
1. Inactivity should be avoided. Some is better than none, especially in low active groups. 2. 75min VPA/week 3. Or 150 MPA/week 4. Or equivalent blend 5. At least in episodes of 10min 6. Preferably spread throughout the week 7. For extensive health benefits, 5h/week MPA 8. Or 150VPA/week 9. Or equivalent combination of MPA and VPA 10. 2x strength training moderate/high intensity per week for bone density health
What are the 2008 PA guidelines for Children?
1. Generally 1h/day MPA-VPA. 2. VPA at least 3d/wk. 3. Muscle strengthening at least 3d/wk. 4. Bone strengthening at least 3d/wk.
What is preload?
Preload–theamountof blood in the ventricles before contraction ♥ End diastolic volume About 100mL
What is afterload?
Afterload=the amount of blood left in the ventricles after contraction ♥ End systolic volume About 40mL
What is the ejection fraction?
SV/EDV x 100 = ((EDV-ESV) / EDV)) x 100 Approx at rest 70%
What is Q?
Cardiac output = HR (bpm) x SV
What is SV?
Stroke volume End Diastolic Volume – End Systolic volume Preload - afterload
What is shortening fraction?
((EDD - ESD) / EDD) x 100 Approx at rest 35%
What triggers the cardiovascular response?
Efferent signals: Balance between (PNS/vagus and SNS/cardiac) autonomic branches to control myocardial contraction.