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Introduction
• Physical activity is any form of movement that works muscles and
uses more energy than when resting.
Eg :- Walking, running, dancing, swimming, yoga, gardening..
• Lack of physical activity is clearly shown to be a risk factor for
coronary heart disease (CHD) & coronary arteries diseases
(CAD).
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• He established the importance of physical activity in preventing
CVD.
• Examined the onset of coronary artery disease in 31000 male
transport workers aged 35 to 65 years .
• Main objective - “seek for relations between the kind of work men do
and the incidence among them of CAD.”
• Examined the bus, tram, and trolleybus conductors, who climbed 500
to 750 steps per working day on average, and the drivers, who sat
for over 90% of their shift. (overall annual incidence 2.7/1000 versus
1.9/1000)
• The sedentary drivers had higher rates of cardiovascular disease
than the conductors.
.
Jeremy Morris et al (1949)
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Criticism
• His study could not prove physical activity prevents CHD.
• Also the workers may have been selected on the basis of their body
type, personality or some other factor associated with high or low risk
of CHD .
British Civil Servant
• Prospective study of middle-aged male civil servants who held
sedentary desk jobs.
• Over the 3-year follow-up period they recorded 232 first clinical CAD
events.
• These affected individuals were then matched to two non- affected
individuals with subsequent finding that men who recorded vigorous
activities (peak energy output of 7.5 kcal/minute) had a 33% relative
risk of developing CAD.
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• He investigated the relationship between physical activity and CVD among the postal
workers of Washington.
Results
• He found low CHD rates among active workers.
• But their CHD changed when they switched to more sedentary lifestyle; clerks.
• After 5 yrs their incidence of death from CHD was equal to that of men who has always
been clerks.
• He performed further studies that showed slow movements such as gardening helped
very little and exercise had to be more vigorous to help. His study dealt with a
population that minimizes the possible effects of socioeconomic variation on CHD
incidence, while at the same time important differences in on-the-job physical activity
are included.
• Criticism
• His study showed that workers who are physically active have reduced risk of CHD. He
did not measure the activity level of workers off the job.
• Age factor was ignored.
Harold Kahn (1963)
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Ralph Paffenbarger (1950-51)
• Epidemiologist, and professor at both Stanford University School of Medicine
and Harvard University School of Public Health.
College Alumni Health Study
• investigating the exercise habits of males of University of Pennsylvania
& Harvard University alumni.
• They sent questionnaire to the men.
• They measured weekly total energy expenditure by
using a composite physical activity index.
Ex :- flight of stairs per day (10 steps) accounted for 28 kcal/week energy
expenditure.
• They divided the groups into low-energy (less than 2000 kcal/week) and
high-energy categories (more than 2000 kcal/week).
• Cohort included 36500 male alumni who entered college from 1916 to 1950.
• At time of enrollment it was customary to have a routine physical
examination, thus providing an extensive baseline record.
Results
• Less active alumni had an increased risk of heart attack as compared to
those who were active.
• When combined with the other independent risk factors of smoking or
hypertension, they found that the presence of all three conferred a relative
risk of 7.70, as opposed to 2.78 for the presence of any two factors and 1.50
for any one factor.
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Other Studies….
• Leon et al. (1997) studied 12,138 middle-aged men for 16 years; 29% lower CHD
mortality and a 22% lower all-cause mortality for least vs. moderately active.
• Rosengren et al. (1997) studied 7142 men in Sweden aged 47-55 followed for 20
years ; RR=0.72 for CHD death and RR=0.70 for total mortality in most vs. least
active.
• Blair et al. (1989) followed 10,224 men and 3,120 women for 8 years; RR=1.58 for
men and 1.94 for women for all-cause mortality in those in lowest vs. highest
fitness quintile.
• Ecklund et al. (1988) showed in 4276 men aged 30-69 followed 10 years RR for
CVD mortality of 2.7 and CHD death 3.2 per 35 beats/min from submaximal
treadmill testing
• Study of 3331 Japanese men showed frequency of physical activity related to
HDL and number of risk factors--those who exercised 1,2, and >=3 days per
week had 1.38, 1.19, and 0.99 risk factors.
• PEPI study showed in 851 post-menopausal women self-reported physical
activity positive associated with HDL and inversely related to insulin and
fibrinogen
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Later Studies
Toronto Symposium (2000): Evidence for dose- response relationship
• PURPOSE:
To summarize and synthesize existing literature providing evidence of a dose-
response relation between physical activity and CVD endpoints.
• Findings supplemented by existing consensus documents and other published
literature. Only studies with greater than two physical activity exposure
categories were included.
• Existing studies were classified by outcome used: all cardiovascular disease
(CVD), coronary (ischemic) heart disease (CHD), and stroke.
• Prospective observational studies and has been conducted in European men or
populations of men of primarily European descent.
• Follow-up intervals ranged from 3 to 26 yr.
• Consistent inverse relation was found.
• Methodological advances in physical activity assessment; additional studies on
changes in the physical activity, as it relates to the outcome.
• More studies among women and ethnically diverse populations are needed to
clarify these relations.
•
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Do Women & Men Benefit
Equally??
Iowa Study
• Postmenopausal women
• Older women who exercised 4 times a week
had much lower rates of all- cause mortality
than women who were sedentary.
• Vigorous activity also reduced death rates but
was not superior to moderate.
Nurses’ Health Study
• Middle aged and older women can reduce their risk of death
by 20-30% and benefits CVD more than cancer.
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Ralph Paffenbarger et al
• 37 prospective cohort study & 1 retrospective study that dealt with all-cause mortality
and both PA & Physical fitness in women.
5 Q’s
1. Do highly active women postpone their death by their PA?
2. Do gender- differences exist regarding PA & all –cause mortality?
3. Is there a dose-response relationship between levels of activity in women and
mortality?
4. How much activity is required for women to benefit?
5. Does age play a role?
ANSWERS
1. Inactive women were much more likely to have died during the study.
2. Studies were almost the same as that of men.
3. Evidence is not robust for a dose response relationship.
4. Energy expenditure of 1,000 calories is probably
adequate to avoid premature death.
5. Women below 55 benefit more.
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Conclusion
• Excluding disability and potential health conditions, men and women both stand to benefit from
physical exercise, although their motivation for partaking in physical activity is believed to hold
variance.
• Marks et al., (2006) state that women pursue physical activity as a means to maintain a positive
body image while men pursue physical activity through the reward of engaging in sport and
maintaining fitness.
• San Antonio Heart Study conducted by Rainwater et al., (2010) did find that a change in physical
activity over a five-year period reduced cardiovascular risk factors to a slightly greater degree in
men as opposed to women.
• However, a majority of current research suggests that men and women both physiologically
benefit from physical exercise equally.
• At least 150 minutes of exercise each week to help control weight and keep your body healthy.
• Physically active people increase their longevity of about 2 yrs.
• Both women & men who smoke, are overweight, have high cholesterol level can lower CVD risk
by engaging in light to moderate exercise.
•
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Physical Activity & Cholesterol
Levels
• A waxy, fat-like substance, serves necessary functions within the body, including the
production of hormones, the support of cellular membranes and the production of bile
acids necessary for digesting fats.
• Too much cholesterol causes formation of plaque.
• Plaque restricts the flow of blood to the heart, causes heart disease and can lead to a
heart attack or stroke.
• Both diet and physical activity level affect cholesterol levels.
• Researchers now believe there are several mechanisms involved. First, exercise
stimulates enzymes that help move LDL from the blood (and blood-vessel walls) to the
liver.
• From there, the cholesterol is converted into bile (for digestion) or excreted. the more is
the exercise, the more LDL is expelled.
• Second, exercise increases the size of the protein particles that carry cholesterol
through the blood. (The combination of protein particles and cholesterol are called
"lipoproteins;" it's the LDLs that have been linked to heart disease).
• Some of those particles are small and dense; some are big and fluffy. "The small,
dense particles are more dangerous than the big, fluffy ones because the smaller ones
can squeeze into the [linings of the heart and blood vessels] and set up shop there.
• But now it appears that exercise increases the size of the protein particles that carry
both good and bad lipoproteins.
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• 2 major types of cholesterol: low-density lipoprotein, or LDL, and high-density lipoprotein,
HDL.
• HDL helps to remove excess cholesterol from the body, so the higher the level the lower
the risk for heart disease.
• Participating in frequent aerobic physical activity increases your HDL by 5 percent over
your cholesterol level at a sedentary lifestyle.
• Some researchers conducted experiments on monkeys & found PA reduced cholesterol
& artherosclerosis.
• PA without dietary changes reduces Cholesterol level among humans by bringing total
cholesterol to HDL.
• Review of Toronto Symposium found that walking & gardening increases HDL & reduced
VLDL & LDL.
• Moderate activity reduces HDL but strenuous activity does not provide extra benefit.
• In a study of overweight, sedentary people who did not change their diet, the researchers
found that those who got moderate exercise (the equivalent of 12 miles of walking or
jogging per week) did lower their LDL level somewhat.
• But the people who did more vigorous exercise (the equivalent of 20 miles of jogging a
week) lowered it even more.
• More vigorous aerobic activities, such as brisk walking, running, swimming, bicycling,
roller skating, and jumping rope—done most days of the week for at least 30 minutes—
are best for improving the fitness of the heart and lungs.
• Moderate levels of physical activity confer significant health benefits.
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Conclusion
• People can gain benefit when they move from sedentary lifestyle to active one.
• Walking especially for older people protects against CVD.
• Inactive lifestyle = Diabetes, High Cholesterol level, Smoking, High BP.
• Physically fit men & women can reduce their CVD risk by indulging in leisure- time
activities.
• Exercise does years ago cannot provide much protection against all- cause mortality.
• Moderate to intense activity can reduce risk for heart disease.
Ex- Nurses’ Health Study showed that active women
reduced their risk of ischemic stroke by 34% as
compared to sedentary lifestyle women.
• Meta – analysis found that high levels of occupational and leisure-time
physical activity can reduce risk of both ischemic stroke & hemorrgraphic
stroke.
• Lifestyle that has some physical activity can help protect against premature
CVD.
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Conclusion
• Men, women 7 children of all ages benefit with physical
exercise.
• To reduce Cholesterol High intensity exercise benefits
more than moderate exercise.
• “Some exercise is better than none; more exercise is
better than some.”
“Love Yourself”
