NUTRITION IN SPORT

1986); the risk of first attack was one quarter to
one third lower in men who expended more than
8.36 MJ · week–1 (2000 kcal · week–1) in physical
activity (sports, garden work, walking, stair-
climbing, etc.) than in classmates whose
exercise energy expenditure was lower, i.e. high
total energy expenditure in exercise was a
determinant of risk.
By contrast, prospective study of English civil
servants found no association between total
exercise energy expenditure and risk of heart
attack (Morris et al. 1990); only men reporting
‘vigorous’ exercise experienced a lower risk than
sedentary men. Vigorous was defined as exercise
likely to involve peaks of energy expenditure of
31 kJ · min–1 (7.5 kcal · min–1) or more. This is
about the rate of energy expenditure of a middle-
aged man of average weight during fast walking,
so it is not surprising that men who reported
that their usual speed of walking was ‘fast’
(>6.4 km · h–1) experienced a particularly low rate
of attack. Low rates were also reported for men
who did considerable amounts of cycling.
Increasingly, studies have measured physical
fitness rather than, or as well as, physical activity.
Their findings are broadly similar, i.e. a two- to
threefold increase in the risk of cardiovascular
death in men when comparing the least fit with
the most fit groups (Whaley & Blair 1995). The

limited data available suggest an effect of at least

this magnitude for women.

Given the diverse methodologies and cohorts

studied, the clarity with which the inverse,

graded relationship between level of physical

activity or fitness and risk of mortality from CHD

emerges is noteworthy. Figure 3.1 summarizes

the findings of seven studies in which either

leisure time activity (questionnaire) or fitness

(laboratory exercise test) was assessed prior to a

follow-up period of 7–17 years. The precise

pattern differs between studies, but it is clear

that, whilst men with only moderate levels of

activity or fitness experience some degree of pro-

tection, higher levels tend to confer greater

protection. Some studies, however, suggest that

the relationship may be curvilinear—CHD risk

decreasing steeply at the lower end of the contin-

uum, reaching an asymptote in the mid-range.

Thus, for men in the age group most studied

(approximately 40–60 years), values for V

.

o2max.

of around 35 ml · kg–1· min–1have been proposed

as being sufficient to confer a worthwhile—not

necessarily optimal—decrease in risk; evidence

for women is scanty, but a comparable value is

probably at least 2 or 3 ml · kg–1· min–1lower.

Two aspects of the evidence strengthen the

argument that the relation of activity and fitness

with CHD risk may be causal. First, only current

exercise, nutrition and health 41

Fig. 3.1The relationship between the level of physical activity (Paffenbargeret al. 1986; Ekelund et al. 1988; Morris
et al. 1990; Leon 1991; Shaper & Wannamethee 1991) or fitness (Blair et al. 1989; Sandvik et al. 1993) and risk of
coronary heart disease among men in prospective studies. Adapted from Haskell (1994).

+

+

+

+

+

+

100

80

60

40

20

0

Reduction in coronary

events/mortality

Physical activity/fitness level

Paffenbargeret al., 1986

Morriset al., 1990

Blairet al., 1989

Leon, 1991

Ekelundet al., 1988

Sandviket al., 1993

Shaper & Wannamethee, 1991