9
above the guideline was modest, leading Arem and colleagues [ 46 ] to describe an
‘L-shaped’ association. We have used data from the Scottish Health Survey (SHS)
and the Health Survey for England (HSE) to examine the relationships between
physical activity and health. We investigated associations between physical activity
patterns and mortality in more than 60,000 participants in SHS and HSE [ 47 ].
Leisure-time physical activity was assessed and participants were defined as inac-
tive (reporting no moderate-intensity or vigorous-intensity activities), insufficiently
active (reporting less than 150 min per week of moderate-intensity and less than
75 min per week of vigorous-intensity activities), weekend warrior (reporting at
least 150 min per week of moderate-intensity or at least 75 min per week of
vigorous- intensity activities from one or two sessions), and regularly active (report-
ing at least 150 min per week of moderate-intensity or at least 75 min per week of
vigorous-intensity activities from three or more sessions). All-cause mortality risk
was approximately 30% lower and CVD mortality risk was approximately 40%
lower in active versus inactive participants; active included the weekend warriors
who performed all their exercise in one or two sessions per week. The weekend war-
riors took part in a relatively high proportion of vigorous-intensity activity and we
concluded that quality might be more important than quantity. Vigorous-intensity
activity increases cardiorespiratory fitness more than moderate-intensity activity
and cardiorespiratory fitness may be a stronger predictor of mortality than smoking,
high cholesterol, high blood pressure and other established risk factors [ 48 ].
Few epidemiological studies have been designed to examine the mechanismsthat mediate the cardio-protective effects of physical activity. In a study of 27,
apparently healthy women followed for 11 years, most of the reduced risk of CVD
associated with being physically active was explained by risk factors measured by
the investigators, including inflammatory/haemostatic biomarkers (which explained
33% of the reduced risk), blood pressure (27%), traditional lipids (19%), adiposity
(10%), and glycaemic control (9%) [ 22 ]. More observational cohort studies and
exercise interventions are required to determine whether novel biomarkers explain
the ‘protective effect’ of physical activity in men.
4.2 Exercise Interventions
Although the large population studies have been invaluable in establishing associa-
tions between physical activity and CVD, observational studies are prone to bias
(that is, the inferential error associated with any process that causes results to vary
systematically from the truth). Randomised controlled trials (RCTs) can provide
important information on the effect of exercise frequency, exercise intensity, and
exercise duration on various CVD risk factors. The findings from some of the larger
studies, meta-analyses and systematic reviews on modifiable CVD risk factors are
described below.
1 Physical Inactivity and the Economic and Health Burdens Due to Cardiovascular...