Re adin ess for Phys ical Act ivit y

Ro y J. She phar d

UNI VERS ITY OF TOR ONTO 

ORIGINALLY PUBLISHED AS SERIES 1, NUMBER 5, OF THE PCPFS RESEARCH DIGEST.

HI GHLI GHT

“T h e ri sk t h a t ex erci se wi ll in d u ce a ca rd ia c ca t a st rop h e is lo w

a n d m a n y sc reen in g t e st s a r e co st ly a n d t i m e co n su m in g. Th e

re vise d PA R-Q h a s sh own re m a rk a ble su cces s a s a n ex erci se

sc reen in g p r oced u re a n d is re com m en d e d fo r sy m p t o m -fr ee

a d u lt s wi t h n o m o re t h a n on e m a jor ca rd ia c ri sk fa ct or .”

Current practice in physical education and sports medicine emphasizes the twin goals of

reducing the risk of illness and increasing quality-adjusted life expectancy through the

development of health-related fitness (Bouchard et al., 1990; Bouchard et al., 1994; US

Surgeon General, 1996). The average city-dweller currently takes insufficient habitual

physical activity to realize these goals, but involvement in a regular, well-designed program of

aerobic training, supplemented by moderate resisted muscle exercises, could satisfy both

objectives (American College of Sports Medicine (ACSM), 1991; ACSM, 1993). What are the

risks of engaging in such activity, and how can a person determine if he or she is ready to

undertake such a program?
RI SKS OF E XERC ISE

Excessive physical activity can provoke a variety of musculoskeletal injuries, but the big fear,

highlighted by such events as the sudden death of Jim Fixx and other high-profile exercisers,

is that the program will provoke a fatal heart attack. Studies from our own laboratory and

elsewhere (Cobb & Weaver, 1986; Northcote & Ballantyne, 1984; Sadaniantz & Thompson,

1990; Shephard, 1974, 1981, 1995; Siscovick, 1990; Thompson & Fahrenbach, 1994; Vuori,

1995) show that (at least in symptom-free men) the risk of fatal and nonfatal heart attacks

during physical activity is from 4 to 56 times higher than it is while sitting at home reading a

book. The issue of hypertrophic cardiomyopathy and sudden death is controversial (Maron,

Isner, & McKenna, 1994; Rost & Hollman, 1992; Shephard, 1996a, b). Maron et al. (1986)

suggested that the main causes of sudden death in exercisers under 35 years of age were

hypertrophic cardiomyopathy (48%: particularly a thickening of the septum between left and

right ventricles) and unexplained enlargement of the left ventricle (18%). However, the norms

of wall thickness are still not agreed upon, and the prevalence of the disorder is so low that

routine electrocardiographic and/or echocardiographic screening of young adults is not

warranted; indeed, such an approach yields many false positive diagnoses, with resulting

anxiety and iatrogenic invalidism (Shephard, 1996a, b). In those over the age of 35 years,

80% of exercise-related deaths were attributed to disease of the coronary arteries. The overall

risk that vigorous physical activity will provoke a cardiac emergency is quite low, about one

death per 400,000 hours of jogging (Thompson et al., 1982), and furthermore the risk seems

even lower in regular than in occasional exercisers (Siscovick et al., 1984).

IM PLIC ATIO NS F OR P RE-E XERC ISE SCRE ENIN G

Ideally, regular physical activity should be conceived as a simple, safe, and natural part of

healthy living, a lifestyle to which the human body has adapted over many centuries of

evolutionary struggle as a hunter and primitive agriculturalist (Shephard, 1993), rather than as

a dangerous medical intervention that requires extensive, high-technology pre-exercise

evaluation.

For a long period, physicians in the United States adopted a somewhat restrictive

approach to exercise prescription, suggesting that a stress electrocardiogram was needed in all

men over the age of 35 years who wanted to increase their habitual physical activity (Cooper,

1970). Their starting point was the now largely discredited assumption (Shephard, 1984;

Siscovick et al., 1991) that echocardiography and/or a medically supervised exercise stress

ECG could predict and thus avert the occasional exercise-induced cardiac arrest. Northcote

and Ballantyne (1984) have pointed out that it would cost $13 billion to screen even current

athletes over the age of 35 years; moreover, it would be necessary to screen 10,000 potential

exercisers to find one who might die, and four other individuals who had been cleared by

exercise stress testing would die unexpectedly while exercising (Epstein & Maron, 1986).

Finally, the stress test itself has a significant morbidity and mortality (Van Camp, 1988), and a

heavy emotional, financial, and medical burden is generated by the high proportion of false

positive test results.
The need for extensive preliminary screening is particularly questionable, given that

moderate exercise decreases rather than increases a person’s overall risk of cardiac death

(Siscovick et al., 1984). The Swedish physiologist P. O. Astrand has often suggested in his

lectures that it would be more logical to focus detailed medical attention on sedentary people

than on those who are about to enter a conditioning program. Nevertheless, potential

exercisers can be offered some practical advice that will reduce the likelihood of an exercise

catastrophe. A review of such incidents (Johnson, 1992; Shephard, 1974, 1981, 1995)

suggests that risks are increased if:

1.There is a history of fainting or chest pain during exercise.

2.There is a family history of sudden death at a young age.

3.The intensity and duration of activity are much greater than the subject has recently

experienced.

4.Competition, publicity, or pride encourages persistence with exercise in the face of warning

symptoms.

5.The individual exercises while under pressure of time, or when oppressed by business or

social problems.

6.The activity involves heavy lifting or prolonged isometric effort.

7.The weather is unduly hot or cold.

8.The participant has a viral infection, senses chest discomfort or cardiac irregularity, or feels

“unwell.”

9.Exercise soon after rising from bed (Willich, 1995).

The corresponding precautions are all matters of common sense, readily understood by

the general public, but rarely discussed in the course of the usual clinical examination. There

has thus been increasing acceptance of the Canadian viewpoint (Shephard, 1976, 1988, 1994),

that (in symptom-free people from adolescence through to early old age) simple advice and

self-administered questionnaires provide the most appropriate method of determining

readiness for a modest increase of physical activity.

Cu r r en t U. S. S cr ee n in g Rec om m e n dat ion s 

The current U.S. recommendation for pre-exercise screening has moved much closer to the

Canadian position (Table 1.1). It looks at the age of the subject (males >40 and females >50

years, American College of Sports Medicine, 1991, p. 37), the proposed intensity of effort,

and associated symptoms or major cardiac risk factors.

TA BLE 1 .1

I n dica tion s f o r p r elim in ar y m e dica l sc r een in g am on g th ose wh o wi sh to 

in cr ea se th eir h a b it u al p h y sic al ac tiv i ty (b ased on th e r e com m en da tion s of 

th e Am er ic an Co lleg e of Sp or ts Me dici n e, 19 91; se e or ig in al ar ticl e f o r

de tail s).

Va r i ab l e In di ca t i on fo r Me di ca l Sc r een i ng

Kn own dise ase Ye s, i f ca rdia c, p ulmo nary , or met abol ic

Sy mpto ms o r si gns Ye s, i f ca rdia c, p ulmo nary , or sug gest ing dise asea me tabo lic

Ma jor card iac risk Ye s, i f tw o or mor e fa ctor sb
Vigorous exercisec Yes, if man >40 yr or woman >50 yr

aPain or discomfort in chest, shortness of breath with mild exertion, dizziness or sudden

loss of consciousness, shortness of breath while sleeping, swelling of the ankles,

palpitations or racing heart beat, pain in the calves on walking, or known heart murmur.

bBlood pressure higher than 160 mm Hg systolic or 90 mm Hg diastolic on two occasions,

or use of medication to reduce blood pressure; serum cholesterol higher than 6.2 mmol/L

(240 mg/dL); cigarette smoking; diabetes mellitus; family history of coronary o r

atherosclerotic disease in parents or siblings before the age of 55 years.

cExercise that represents a substantial challenge; usually higher than 60% of maximal

oxygen intake, and causing fatigue within 20 minutes or less.

If the subject is planning no more than a moderate increase of habitual activity (an

intensity of less than 60% of peak aerobic effort, which the person can sustain comfortably

for an hour or longer), is symptom-free and has no more than one major coronary risk

factor, then a preliminary medical examination is no longer recommended. Indications for

medical advice are (1) the presence of disease, (2) the intent to undertake vigorous exercise

above the specified age limit, and (3) two or more major risk factors, or symptoms suggestive

of cardiopulmonary or metabolic disease.

Si m ple App r oac h es to S cr ee n in g 

Although the expense and anxiety associated with a formal medical examination are

unwarranted for the great majority of people who plan to begin a simple exercise program,

there remains merit in simple screening procedures, either self-administered or carried out by

the staff of a fitness center.

Bailey et al. (1976) first suggested such an approach when screening candidates for the

Canadian Home Fitness Test. In the following year, Chisholm and associates (1975, 1978)

surveyed 1,253 apparently healthy adults who were attending an exhibition. They evaluated a

potential list of some 19 self-administered screening questions against a medical examination

that included a physical examination, the measurement of resting blood pressure, and

recordings of resting and exercise electrocardiograms. As a result of this research, a brief selfadministered questionnaire (the Physical Activity Readiness Questionnaire, or PAR-Q) was

developed. This incorporated the seven questions they judged had been the most effective in

identifying individuals who needed a medical examination prior to exercise testing or

conditioning.
The original version of the PAR-Q was quickly endorsed by the Canadian federal

government fitness agency (Fitness Canada), and it has since been widely used, both in

Canada and abroad (Shephard, 1986). Indeed, the American College of Sports Medicine

recently recommended adoption of the PAR-Q procedure for healthy adults (men >40,

women >50 years) who wish to increase their habitual physical activity (American College of

Sports Medicine, 1991). Nearly two decades of experience has shown that the original PAR-Q

procedure is remarkably safe (Shephard 1988, 1991). Given the low inherent risk of exercise

for the healthy adult, and the fact that even clinical examination and an exercise stress ECG

provide a rather dubious “gold standard” of exercise readiness, it is difficult to assess the

sensitivity (the percentage of subjects unready for exercise who are detected) and the

specificity (the percentage of individuals who are screened needlessly) of the PAR-Q

procedure. Sensitivity seems adequate, since the PAR-Q has been used to screen as many as

half a million people, without any reported adverse events in subsequent exercise testing or

programs. On the other hand, about 20% of would-be exercisers “fail the test” by

responding positively to one or more questions (Shephard et al., 1981), and in those aged

60–69 years, as many as 55% are “screened out” (Fitness Canada, 1983; Shephard, 1986).

Moreover, subsequent examination of the medical records, blood pressure readings, and

electrocardiograms on positive responders suggests that at all ages from adolescence onward,

many of the PAR-Q exclusions are unnecessary (Shephard et al., 1981).

Accordingly, the detailed wording of individual PAR-Q questions has recently been

reviewed and revised by an expert committee of Fitness Canada (Figure 1.1). Given the

absence of any clear gold standard of exercise readiness, the rewording was agreed through

the Delphic process of circulating repeated drafts of the questionnaire for critical comment.

The principal objective was to increase specificity without an undue sacrifice of sensitivity.

The revised wording of the questionnaire reduced the overall number of individuals who were

“screened out” from 17% to 12%. In all, 7.3% who had originally made positive responses

were cleared by the rPAR-Q, but 2.3% of new candidates were cautioned about exercising

(Shephard, Thomas, & Weller, 1991).

FI GURE 1 .1 

Revised physical activity readiness questionnaire (rPAR-Q).

Ye s No 

1. Ha s a doct or s aid that you hav e a hear t co ndit ion and reco mmen ded only med ical ly s uper vise d ac tivi ty?

2. Do you hav e ch est pain bro ught on by p hysi cal acti vity ?

3. Ha ve y ou d evel oped che st p ain in t he p ast mont h?

4. Do you ten d to los e co nsci ousn ess or f all over as a re sult of dizz ines s?

5.Do you have a bone or joint that could be aggravated by the proposed physical activity?

6.Has a doctor ever recommended medication for your blood pressure or a heart condition?

7. Are you aware through your own experience, or a d octo r’s advi ce, of a ny o ther phy sica l re ason aga inst you r

ex erci sing wit hout me dica l su perv isio n?

NO TE: If y ou h ave a te mpor ary illn ess, suc h as a c ommo n co ld, or a re n ot f eeli ng w ell at t his time —

PO STPO NE.

From Shephard, R.J., Thomas, S., & Weller, I. (1991). “The Canadian Home Fitness Test:

1991 Update,” Sports Medicine. 1: page 359, used by permission.
The trend was for the revised format to allow exercise in a higher proportion of elderly

subjects. The largest change of response patterns occurred on the question relating to blood

pressure, which had been a major cause of erroneous exercise exclusions when using the

original PAR-Q (Shephard et al., 1981).

Cu r r en t Ev alu a tion of Scr e en in g Qu esti on n a ir es 

The specificity of any screening test can only be improved at the price of some loss of

sensitivity. A further decade of usage will be needed to decide whether the shift in this

balance has been gauged correctly in the rPAR-Q, although preliminary data are encouraging

in this regard. Unfortunately, there are major obstacles to an objective comparison of the two

questionnaire wordings. Cost is a significant barrier, given the required sample size, but the

cost/effectiveness of a validation against clinical examination is also questionable, given the

lack of agreement between doctors on appropriate criteria for exclusion from conditioning

programs, and the high proportion of false positive stress ECGs in symptom-free adults

(Shephard, 1981). Physician-exclusion rates can range from 1% to 15% in comparable

samples of the general adult population (Shephard, 1988). Moreover, high physician

exclusion rates apparently lack validity, since they do not reduce the number of

electrocardiographic abnormalities and other minor complications that are encountered

during exercise testing.

When developing the original PAR-Q, Chisholm et al. (1975, 1978) did attempt to

validate their list of 19 potential questions against physician records, blood pressures and

electrocardiographic tracings. The final, reduced list of seven questions did not receive any

formal clinical validation. Nevertheless, less direct validation has been possible, coupling the

International Classification of Diseases (ICD) codings reported in a national health survey

(Health & Welfare, Canada, 1982) with PAR-Q responses. Trial of this approach has shown

remarkable success (Arraiz et al., 1992). Over a seven-year follow-up, 1,644 of 31,668

subjects died. PAR-Q responses were divided into three categories: pass (no positive

responses), conditional pass (positive response about hypertension, not under treatment or

supervision for elevated blood pressure), and failure (other positive response). In those failing

the test (Table 1.2), the crude overall mortality risk ratio was 2.2 (or 2.1, after adjustment for

age, sex, body mass index, and smoking behavior). Moreover, the relative risk of

cardiovascular death was 9.1 (or 7.8 after adjusting for age, sex, body mass index, and

smoking behavior). Interestingly, the relative risk was moderately greater than that associated

with a poor performance on the Canadian Home Fitness Test, and was much greater than

would have been obtained by use of an exercise stress ECG. Siscovick et al. (1991) found a

relative risk of only 2.6 when asymptomatic hypercholesterolemic men with exercise-induced

ST segmental depression were followed for a seven-year period. The PAR-Q responses

remained of prognostic value when cases with known heart disease, stroke, and high blood

pressure were deleted (Table 1.2).

TA BLE 1 .2

Validation of the original PAR-Q test against a 7-year prospective study of data

from the Canada Health Survey (data abstracted from the paper of Arraiz et al.,

1992).

So ur ce of Ri sk Re l at i ve Ri sk i f Fa i l ed PA R- Q

Cr ude Ad just ed
Al l ca uses 2. 2 2. 1

Ca rdio vasc ular dis ease 9. 1 7. 8

CV D (o mitt ing if 5. 4 hi stor y of CVD )

CV D (o mitt ing if h isto ry 2. 9 o f CV D, s trok e, H BP)

Ca ncer 2. 1 1. 6

Ot her caus es 2. 4 2. 1

When the Canadian governmental committee revised the PAR-Q, changes from the

original format were deliberately held to minor clarifications of wording, and the number of

questions was unchanged. It already seems a very useful screening tool. However, the

questionnaire may pass through several further revisions and refinements of wording before

all of its potential has been realized. Issues that remain to be addressed include the need for

age-specific questionnaires for children and for the very old, the level of certification needed

by paramedical professionals who are now urged to discuss client responses to questions 5

and 6, the need to caution those cleared by the rPAR-Q against large and sudden increases in

habitual activity, the value of additional questions, and the potential to add information about

lifestyle and conditioning techniques to the back of the questionnaire.

S UM MA RY 

The risk that exercise will induce a cardiac catastrophe is low, and a medically supervised

exercise ECG is not a cost-effective approach to the preexercise screening of symptom-free

adults. However, a questionnaire (whether self-administered, or completed by fitness center

staff) is a useful safety precaution. The Canadian Physical Activity Readiness Questionnaire

(PAR-Q) has proven a very safe screening tool, and comparison of responses with findings

from the Canada Health Survey has shown remarkable success in detecting potential

contraindications to exercise. Nevertheless, the PAR-Q also “screens out” an excessive

proportion of apparently healthy older adults. To reduce unnecessary exclusions, the

questionnaire wording has now been revised (rPAR-Q). The balance of sensitivity to

specificity is apparently improved in the revised questionnaire, particularly in regard to the

question about an elevation of blood pressure. The rPAR-Q is thus the currently

recommended method of determining exercise readiness in symptom-free adults with no

more than one major cardiac risk factor.

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