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Maya Ignaszewski, MD, Benny Lau, MD, FRCPC, Shannon Wong, BSc, Saul Isserow,
MBBCh, FRCPC
The science of exercise
prescription: Martti Karvonen
and his contributions
The work of a founding father of cardiovascular disease epidemiology in Finland suggests that physicians might consider writing
a prescription for exercise before they write a prescription for an
antihypertensive or antihyperglycemic agent.
ABSTRACT: Martti Karvonen was
born in Finland in 1918. He received
a medical degree from the University of Helsinki in 1945 and a PhD
degree from the University of Cambridge in 1950. His contribution to
cardiovascular epidemiology began
in the mid-1950s, when he observed
that serum cholesterol levels were
higher in men living in eastern Finland than those living in western Finland. He brought these observations
to the attention of Ancel Keys, and
the two collaborated on the first epidemiological studies of risk factors
for coronary heart disease. This collaboration ultimately led to the inclusion of Finland in the hallmark
1958 Seven Countries study that
established a relationship between
lifestyle and the prevalence of atherosclerosis. Karvonen also developed a formula that can be used to
determine a target heart rate for
aerobic activity. Although the Karvonen formula can overestimate or
underestimate the exercise intensity in certain patients, it provides
general rule-of-thumb target heart
rates, with light-intensity exercise
being defined as activity using 30%
to 40% of the heart rate reserve,
moderate-intensity exercise using
40% to 60%, and vigorous-intensity
activity using 60% to 90%. Ideally,
physicians should provide patients
with an exercise prescription that
outlines the frequency, intensity,
time (duration), and type of exercise. Exercise prescriptions should
include both aerobic activity and
resistance training. Patients with
underlying cardiac conditions can
benefit from a cardiac rehabilitation
program with pre-participation cardiac assessment and development
of a specialized exercise routine.
This article has been peer reviewed.
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E
xercise physiologist Martti
Karvonen is remembered today as a founding father of
cardiovascular disease epidemiology
and prevention in Finland. He was
born in 1918 and received his medical degree from the University of
Helsinki in 1945 and his PhD degree
from the University of Cambridge in
1950. He then became the director of
the Department of Physiology at the
Institute of Occupational Health in
Helsinki, and eventually went on to
become the director general of that
institute.
Karvonen served as chief physician for both the Finnish air force
(1956 to 1966) and the Finnish army
(1974 to 1978). Even after his retirement he remained active in the medical community and continued to act as
a consultant for the WHO Division of
Cardiovascular Diseases.1
Dr Ignaszewski is a PGY-3 resident in internal medicine at SUNY Upstate Medical
University in Syracuse, New York. Dr Lau
is a cardiologist at Lions Gate Hospital. Ms
Wong is a medical student at the University
of British Columbia. Dr Isserow is a cardiologist at the University of British Columbia.
The science of exercise prescription: Martti Karvonen and his contributions
Karvonen’s upbringing in North
Karelia, a rugged part of eastern Finland, defined his approach to cardiovascular medicine. It became apparent to him that many men in the area
were dying of heart disease after
returning from service in the Second
World War. He noticed that the local
diet was rich in calories and fat, and
observed that serum cholesterol levels in men from eastern Finland were
higher than those of men in western
Finland. Karvonen became interested
in understanding the reason for cultural differences in cardiovascular
event rates and the role of diet in the
development of atherosclerosis.1
Karvonen’s pioneering work in
cardiovascular epidemiology began
in the mid-1950s when he brought his
observations about Finnish males to
the attention of Ancel Keys, and the
two scientists undertook the first epidemiological studies of risk factors
on coronary heart disease in eastern
and western Finland. Their collaboration eventually led to the inclusion of
Finland in the hallmark 1958 Seven
Countries study that established a relationship between lifestyle and the
prevalence of atherosclerosis in various parts of the world.
In 1972 Karvonen’s advice
resulted in the creation of the North
Karelia Project, a community-based
program to address the high burden
of coronary heart disease affecting
the area. This program was credited with triggering major lifestyle
changes across Finland, which in
turn led to reductions in mean serum
cholesterol and blood pressure levels, lower smoking rates, and, most
important, a reduction in cardiovascular disease mortality rates and
stroke-related risk factors.2 In 1979
Karvonen’s 12-year Finnish Mental
Hospital study proved that a diet low
in cholesterol was associated with
reductions in coronary heart disease,
and the field of preventive cardiology was born.3
The Karvonen formula
and exercise intensity
While Karvonen played a major role
in establishing a link between lifestyle
factors and cardiovascular events, he
is also known for developing a formula to determine a target heart rate
(HR) for aerobic activity.
We know now that the intensity
range to improve and maintain cardiorespiratory fitness is broad and
depends on a number of factors,
including age, underlying health,
individual physical activity habits,
and baseline functional status. Davis
and Convertino found the Karvonen
formula to be a reasonably accurate method for estimating exercise
intensity.5 Despite occasionally over-
While Karvonen played a major role in
establishing a link between lifestyle factors
and cardiovascular events, he is also known
for developing a formula to determine a
target heart rate for aerobic activity.
In the Karvonen formula, peak HR
is the maximum heart rate achieved
during exercise stress testing and K
is a coefficient: target HR = resting
HR + (peak HR – resting HR) x K.
In a study published in 1957, Karvonen examined the effect of different training intensities on resting,
working, and maximum heart rates.4
He found that training at an intense
level will cause a decrease in working
heart rate, which is a direct indication
of increased peak oxygen consumption and cardiorespiratory fitness. He
identified the threshold at which improvements are seen as 60% of the
heart rate reserve (HRR), which is
expressed as the difference between
the peak heart rate and resting heart
rate. Although the benefits of exercise were well documented, this finding was monumental in defining the
parameters for exercise intensity that
produced tangible results.
estimating or underestimating exercise intensity in certain patients, the
formula provided general rule-ofthumb training heart rates, with lightintensity exercise defined as activity
using 30% to 40% of the heart rate
reserve, moderate-intensity activity
as using 40% to 60% of HRR, and
vigorous-intensity activity as using
60% to 90% of HRR.
There are several methods for
determining exercise intensity that
differ from the Karvonen formula.
When cardiopulmonary exercise testing is available, a percentage of either
the oxygen uptake reserve or the
maximal oxygen uptake can be calculated. Measures of absolute intensity
include metabolic equivalent tasks
(METs), absolute oxygen uptake, and
caloric expenditure. Unfortunately,
these methods do not account for
individual differences and commonly
misclassify exercise intensity. Several
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The science of exercise prescription: Martti Karvonen and his contributions
subjective tools of determining exercise intensity have also been developed and can be used as adjuncts to
the objective methods. These include
the Borg Rating of Perceived Exertion (RPE) scale, the talk test, and the
OMNI scale.
involves the repetitive, rhythmic motion of large muscle groups, and can
be seen in activities such as running
and cycling. For those unaccustomed
to regular exercise, aerobic activity
should begin at a lower intensity and
shorter duration, with gradual pro-
Although the benefits of regular
physical activity are well known,
physicians are often uncertain how to
provide appropriate recommendations
when patients ask for advice.
Exercise prescription
Although the benefits of regular
physical activity are well known,
physicians are often uncertain how
to provide appropriate recommendations when patients ask for advice.
Ideally, physicians should provide
patients with an exercise prescription
based on the FITT-VP6 principle:
Frequency: How often to exercise.
Intensity: How hard to exercise, as
determined by methods described
above.
Time: Duration of each exercise session.
Type: Kind of exercise.
Volume: Product of frequency, intensity, and time to give an overall
estimate of energy expended when
following the exercise prescription.
Progression: Rate of progression for
frequency, intensity, and time.
Exercise prescriptions should include both aerobic activity and resistance training. Aerobic activity
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gression over time until target volume
is achieved. In general, exercise time
should be increased before intensity
is increased. An example of a reasonable progression would be an increase
of 5 to 10 minutes per session every 1
to 2 weeks.6
The benefits of aerobic activity
can also be obtained from interval
training , which involves highintensity exercise interspersed with
light-intensity activity or rest. Aerobic interval training can result in a
larger increase in peak oxygen consumption than continuous training,7
and may be most useful for those at
the extremes of exercise capacity.
For adults, the American Heart
Association (AHA) currently recommends 30 minutes of moderateintensity aerobic activity at least 5
days a week for a total of 150 minutes,
or 25 minutes of vigorous-intensity
aerobic activity at least 3 days a week
for a total of 75 minutes, or a com-
59 no. 1, january/february 2017 bcmj.org
bination of moderate-intensity and
vigorous-intensity aerobic activity and moderate- to high-intensity
muscle strengthening activity at least
2 days a week for additional health
benefits. If the goal is to lower blood
pressure or cholesterol levels, an
average of 40 minutes of moderateto vigorous-intensity aerobic activity
3 to 4 days a week is recommended.8
With the recent increase in childhood obesity, physical activity is becoming increasingly important for
children. Currently, the AHA recommends that all children older than 2
years participate in at least 60 minutes
a day of enjoyable, moderate-intensity
physical activities that are developmentally appropriate and varied. If
scheduling a full 60-minute break for
daily activity is impossible, children
should have at least two 30-minute
periods or four 15-minute periods to
engage in vigorous-intensity physical
activities appropriate for their age,
gender, and stage of physical and
emotional development.9
It is known that the increased
muscular strength resulting from resistance training is associated with
decreased risk of all-cause mortality.10
Other benefits of this type of exercise
include reductions in functional limitations, improvements in self-efficacy
and quality of life, and increases in
bone mass and strength. The current recommendation is to train each
major muscle group against resistance 2 to 3 days a week, with two
to four sets during each session and
eight to twelve repetitions per set.6
The intensity of resistance should
be approximately 60% to 80% of the
one-repetition maximum for each individual, which can be achieved using resistance bands, free weights,
machines with stacked weights, or
pneumatic resistance.
It is also important to note that
physical inactivity is associated with
The science of exercise prescription: Martti Karvonen and his contributions
inferior health outcomes. Therefore,
in addition to providing exercise recommendations, physicians should
advise patients to reduce time spent
being physically inactive. Lastly,
special attention should be paid to
patients with underlying cardiac conditions who are ready to start an exercise program. These individuals
would benefit most from enrolling in
a cardiac rehabilitation program with
pre-participation cardiac assessment
and development of a specialized exercise routine.
Conclusions
Before writing a prescription for an
antihypertensive or antihyperglycemic agent, physicians might consider
writing a prescription for exercise.
The benefits of physical exercise on
overall health have been known for
centuries, with exercise prescriptions
dating as far back as 600 BC.11
Finland’s Martti Karvonen played
a pivotal role in the science of exercise prescription by helping to establish the link between lifestyle and risk
factor development, and by determining the role of exercise intensity in
improving cardiorespiratory fitness.
The formula he developed remains
one of the most widely used methods
for determining a target heart rate for
aerobic activity.
Physicians are often approached
by patients for advice on exercise and
are in an ideal position to promote
this invaluable behavior by providing
safe, useful, and objective exercise
recommendations.
Competing interests
None declared.
References
1. Pincock S. Martti Karvonen. Lancet
2009;374(9694):972.
2. Puska P. Successful prevention of noncommunicable diseases: 25 year experiences with North Karelia project in Finland. Pub Health Med 2002;4:5-7.
3. Turpeinen O, Karvonen MJ, Pekkarinen
M, et al. Dietary prevention of coronary
heart disease: The Finnish Mental Hospital Study. Int J Epidemiol 1979;8:99-118.
4. Karvonen MJ, Kentala E, Mustala O. The
effects of training on heart rate; a longitudinal study. Ann Med Exp Bil Fenn
1957;35:307-315.
5. Davis A, Convertino V. A comparison of
heart rate methods for predicting endurance training intensity. Med Sci Sports
1975;7:295-298.
6. Pescatello LS, American College of Sports
Medicine. ACSM’s guidelines for exercise
testing and prescription. 9th ed. Phil­
adephia: Wolters Kluwer/Lippincott Williams & Wilkins Health; 2014.
7. Pattyn N, Coeckelberghs E, Buys R, et al.
Aerobic interval training vs. moderate continuous training in coronary artery disease
patients: A systematic review and metaanalysis. Sports Med 2014;44:687-700.
8. American Heart Association recommendations for adults. Updated 27 July 2016.
Accessed 7 November 2016. www
.heart.org/HEARTORG/HealthyLiving/
PhysicalActivity/FitnessBasics/Ameri
can-Heart-Association-Recommenda
tions-for-Physical-Activity-in-Adults_
UCM_307976_Article.jsp#.V2LtfigjmL0.
9. The AHA’s recommendations for physical
activity in children. Updated 18 October
2016. Accessed 7 November 2016.
www.heart.org/HEARTORG/Healthy
Living/HealthyKids/ActivitiesforKids/
The-AHAs-Recommendations-for-Phy
sical-Activity-in-Children_UCM_304053_
Article.jsp#.V2LqyigjmL0.
10.Ruiz JR, Sui X, Lobelo F, et al. Association
between muscular strength and mortality
in men: Prospective cohort study. BMJ
2008;337:a439.
11.Tipton CM. The history of “exercise is
medicine” in ancient civilizations. Adv
Physiol Educ 2014;38:109-117.
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