• to provide a brief synopsis of human evolution and history that is relevant to current physical activity and health behaviours in contemporary society
• define key terms
• highlight recent policy and position statements and guidelines on physical activity
• summarise the evidence linking physical activity with various health outcomes and risks
• review the prevalence and trends in physical activity and sedentary behaviour in selected countries.

• Physical activity: History and evolution
• Behavioural epidemiology framework
• Definitions
• Policy statements
• Health-related outcomes of physical activity
• Patterns and trends of physical activity

• Establish the links between PA and health
• Develop methods for accurately measuring
PA
• Identify factors that influence the level of
PA (’determinants’)
• Evaluate interventions concerning PA
• Translate research into practice
PA: physical activity

Establish links between
PA & health
Determinants Interventions
Translation into practice
Measure
PA

• “there is virtually no way of reverting to our
‘natural’ way of life, but with insight into our biological heritage we may be able to modify the current, self-destructive, elements of our modern lifestyle” (Astrand,
1994)

• Bassett et al., MSSE , 2004, pp. 79-85.
• A test of ‘previous generation’ lifestyles on physical activity and obesity
• Male n=53; female n=45
• Ages 18-75 yrs
• Ontario, Canada

(Bassett et al., MSSE , 2004, pp. 79-85)
25000
20000
15000
Men
Women
10000
5000
0
Sun Mon Tues Wed Thurs Fri Sat

Hrs/wk
45
40
35
30
25
20
15
10
5
0
Male
Female
Vigorous Moderate Sitting
From Bassett et al., MSSE , 2004, pp. 79-85

• Physical activity
• Exercise
• Sport
• Health and well-being
• Mental health
• Determinants/ correlates

• movement of the body produced by the skeletal muscles
• resulting energy expenditure which varies from low to high
• a positive correlation with physical fitness
Caspersen, et al (1985)

• body movement produced by skeletal muscles
• resulting energy expenditure varying from low to high
• planned, structured and repetitive bodily movement
• the objective is to maintain or improve physical fitness
• exercise is positively correlated with physical fitness
Caspersen, et al (1985)

Physical activity that is:
• Rule governed
• Structured
• Competitive
• Involves gross physical movement
• Is characterised by physical strategy, prowess and chance
Rejeski & Brawley (1988)

• Health is multifactorial in nature and includes dimensions of:
• Physical health
• Mental health
• Social health
• The enhancement of well-being
• The absence of disease

• the ability of the individual to perform muscular work
• attributes that people have or achieve that enables them to perform physical activity
• physical fitness is partly related to current physical activity levels ('attributes that people achieve ') and partly a function of heredity ('attributes that people have ').
Caspersen, et al (1985)

• Factors (variables) thought to be
‘determining’ why people are active or not are ‘determinants’
• A better word might be ‘correlates’ because we are not sure if ‘determinants’ are truly causal of physical activity
• Correlates are “reproducible associations that are potentially causal” (Buckworth &
Dishman, 2002).

• Prospective epidemiological studies have established that sedentary living carries at least twice the risk of morbidity and allcause mortality

Low physical fitness as a risk factor for all-cause mortality
RR 2.5
2
1.5
1
0.5
0
5
4.5
4
3.5
3
1 2 3 men women
4 5
Notes: Most fit group is the reference category with relative risk (RR) = 1
1 = low fitness group, 5 = high fitness group (Blair et al., 1989)

• "the inverse association between physical activity and incidence of CHD is consistently observed, especially in the better designed studies; this association is appropriately sequenced, biologically graded, plausible and coherent with existing knowledge. Therefore, the observations reported in the literature support the inference that physical activity is inversely and causally related to the incidence of CHD"
(Powell et al., 1987, p. 283).

• Favourable effects of exercise can be found for hypertension
• Lack of physical activity is a primary risk factor of hypertension
• Moderate aerobic exercise can reduce systolic/diastolic blood pressures by 2.6/1.8 mmHg in normotensives, and 7.4/5.8 mmHg in hypertensives
• If such reductions were made in large sections of the population, particularly for hypertensives, significant public health benefits would accrue.

• 22.1% of men and 22.8% of women in English are obese
• Data suggests that physical inactivity is a primary cause of obesity
• “there is still an overwhelming case in favour of the conclusion that physical activity (especially discretionary leisure-time and recreational physical activity) is strongly related to successful weight maintenance” (Prentice & Jebb, 2000, p.
259).

Prevalence (%) of obesity for English boys and girls 1974-2003
7
4
%
3
6
5
2
1
0
1974 1984 1994 1996-71998-9 2000-
01
2002-
03
Boys 5-10
Girls 5-10
(Stamatakis, et al., 2005)

• Type-2, or non-insulin-dependent diabetes mellitus (NIDDM), is a disorder whereby cells are ‘insulin resistant’, resulting in less glucose being cleared from the blood into the cells
• many industrialised countries will see a doubling of rates of NIDDM over the next 20 years, mainly due to the rise in obesity
• physical activity can increase insulin sensitivity, reduce plasma insulin levels, improve glucose tolerance and reduce the risk of developing adult-onset diabetes, even for those who are overweight

• Glucose tolerance decreases with increased age and obesity, and exercise has been shown to slow this effect
• Diabetes and obesity tend to cluster with other
CHD risk factors. These include raised blood pressure and low HDL cholesterol. This has been termed the ‘metabolic syndrome’ or ‘insulin resistance syndrome’ and is associated with low physical activity and fitness

• evidence has linked physical activity with some forms of cancer
• the complexities of the numerous forms and aetiologies of cancers provides researchers with a difficult problem in identifying links and potential causes
• there is now good, possibly causal, evidence showing an inverse relationship between physical activity and colon cancer and a reduced risk of breast cancer in superior research studies
• moderate exercise can enhance the immune system

• Adequately functioning musculo-skeletal system is very important for functional capacity and quality of life
• A substantial part of the age-related decline in functional capabilities is due to decreased or insufficient physical activity
• Maintenance or improvement in functional capacity may be a critical factor in improving life quality for older adults

• Osteoporosis is the excessive loss of bone mineral content, often resulting in fractures
• It is common in older people, particularly in women
• 15% of bone mass can be lost within the first decade after menopause
• Weight bearing activities, such as walking, are considered the most appropriate for reducing the risk of osteoporosis

• 80% of adults will suffer from back pain at some time in their lives, but only about 10% will seek medical attention
• preventive effects of physical activity are described as ‘medium’ level with ‘weak’ strength in the Chief Medical Officer’s Report (2004)
• Recommendations include the improvement of strength, endurance and flexibility of muscles in the trunk

Physical activity:
• has a small-to-moderate beneficial effect on anxiety reduction and stress reactivity
• has a moderate to large beneficial effect on mild to moderate depression
• has a small effect on self-esteem, and moderately favourable effect on self-perceptions, mood and psychological well-being
• has been associated with positive effects on selected measures of cognitive function and psychological adjustment

• The most commonly cited risks of exercise are sudden cardiac death and musculo-skeletal injury
• Although the risk of sudden cardiac death is elevated with exercise, the balance of cardiac benefit and risk as a result of being an exerciser is positive
• risk of injury may be associated with increased age and body mass index
• knowledge of physical activity-related injuries relative to sedentary cohorts is poor

• Estimates of activity levels will partly be dependent on the method used and how physical activity is defined
• The prevalence of 'aerobic activity' across
Australia, Canada, England and the USA varies between 5 and 15%
• 'moderate activity' varies between 29% and 51%
(including data from Finland)
• Estimates of sedentary adults in these countries varies from 43% to 15%

• A Pan-European study of adults showed that
‘inactivity’, defined as no leisure-time physical activity, was most prevalent in Portugal (60%) and least so in Finland (8%)
• Many European countries have the majority of their adult population participating in more than
210 mins/week of leisure-time physical activity, with only Portugal and Spain below 50%

Percentage of English adults in different age groups reporting no physical activity
45
40
35
30
%
25
20
15
10
5
0
16-24 25-34 35-44 45-54 55-64 65-74 men women
Data from Allied Dunbar National Fitness Survey, 1992

• Studies conducted in Europe, Australia and North America during the late 1980s and early 1990s, have concluded that at least 50% of children and adolescents are insufficiently active for health
• Girls are less active than boys
• There is a steep decline across the adolescent period

• Media-use among western adolescents is approximately 40 hours per week, or just over
5.5 hours per day
• 2.5 to 3 hours per day is devoted to TV viewing
• North American data suggest that 23% of girls and 29% of boys aged 8-16 years watch TV more than 4 hours per day, a level twice that recommended by the American Academy of
Pediatrics

Time use trends for 3-12 yr olds:
1981-1997 (Sturm, 2005)
400
300
200
Mins/week
100
0
-100
-200
-300
Sport TV Play School
Notes: ‘Sport’ includes sport and outdoor activities; ‘play’ includes hobbies; ‘school’ includes school, day care, studying, arts, and reading

• Sedentary people have become more involved in moderate activity, but that vigorous activity has not increased in recent times
• The majority of adults in developed countries appear not to be active enough for optimal health benefits
• Data on young people show them to be reasonably active but a clear downward trend is evident in adolescence

• humans in developed Western societies have lifestyles quite dissimilar to that which our evolution has prepared us for and that this is likely to be a major factor in modern disease patterns
• a number of organisations have supported the promotion of physical activity as an important health behaviour through the publication of policy and position statements
• physical activity has been shown to be beneficial for many health outcomes, including all-cause mortality,
CHD, hypertension, obesity, diabetes and metabolic syndrome, some cancers, immune function, functional capacity and capabilities, musculo-skeletal health, and psychological well-being

• physical activity in the form of vigorous exercise does have risks, such as injury and occasional sudden cardiac death, but the evidence shows that people are at greater risk if they are inactive
• some physically active people may be more likely to adopt other health behaviours, such as non-smoking and healthy nutrition, but evidence is mixed
• data from developed countries show that the majority of the adult population is not active enough for health benefits, although the trends over the past 10 years or so suggest that leisure-time physical activity may have increased in adults
• sedentary behaviours are highly prevalent but evidence shows TV viewing in youth is not strongly associated with a lack of physical activity and rates of viewing may have actually declined