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SPRING 2012
for a prolonged period. Decrease of exercise capacity with
“healthy” aging can be slowed down with regular exercise,
but it cannot be avoided completely. The decrease in exercise
capacity is caused by weakened functions of all the body’s
systems, but we will keep our focus on the heart.
The heart has a natural pacemaker system that controls the
heartbeat and the system of pathways that conduct signals to
the muscle cells throughout the heart. Over time, the pacemaker
loses some of its cells, and pathways may get damaged. These
changes can result in a slightly slower heart rate at rest and
susceptibility to abnormal rhythms like atrial fibrillation.
With age, all structures of the heart become more rigid.
The muscle of the left ventricle gets thicker, and the heart
may increase slightly in size overall while the volume of
the left ventricle may decrease. The heart may fill more
slowly, empty more slowly and, thus, eject less blood into
circulation. The increase in heart rate and cardiac output in
response to physical activity get slower, and the maximums
get smaller (see table). The decreases in maximal heart
rate appear to be an age effect, which is more pronounced
in sedentary people and those with overt cardiovascular
diseases.
Modified from Tanaka H. Age-predicted maximal heart rate. J Am Coll Cardiol, 2001; 37:153-6.
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BOB CO A K L E Y
MaxiMuM heart rate by age
Age (years)
20 30 40 50 60 70 80 90
Traditional estimate (220–age), beats per minute
200 190 180 170 160 150 140 130
Healthy nonsmokers (208–0.7 x age), beats per minute
194 187 180 173 166 159 152 145