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150, external factors no longer influence heart rate, and a linear relationship ex-
ists. As the heart rate rises above 150, the heart rate-oxygen uptake relationship
becomes curvilinear.
The third assumption involves maximal heart rate. Maximal heart rate is
the greatest heart rate that can be measured when an individual is exercising to
the point of volitional fatigue (i.e., exhaustion) during a graded exercise test. Sev-
eral equations have been developed to estimate the average maximal heart rate
for humans:
• Maximal heart rate = 220 minus age (low estimate)
• Maximal heart rate = 210 minus [0.5 x age] (high estimate)
• Maximal heart rate = 226 minus age (estimate for older
individuals)
Maximal heart rate can, however, vary greatly among different
individuals of the same age. One standard deviation is
+
12 bpm, which means
that two-thirds of the population varies an average of plus or minus 12 heart
beats from the average given by a prediction equation. If an individual’s age-pre-
dicted maximal heart rate is higher than that person’s true maximal heart rate,
then his/her estimated VO
2 max
will be an overestimation of the correct or actual
value.
The final assumption addresses the issue of mechanical efficiency. Be-
cause oxygen uptake at any given work rate can vary by approximately 15% be-
tween different individuals, individuals vary in the amount of oxygen they require
to perform a certain exercise workload. Some individuals are more
efficient at performing a given task than others. As a result, the average
oxygen consumption associated with a given workload may vary significantly
from one person to another. Thus, VO
2 max
predicted by submaximal exercise tests
tends to be overestimated for those who are mechanically efficient and underes-
timated for those who are inefficient.
The point to remember is that submaximal exercise testing, though not
as precise as maximal exercise testing, is not without advantages. For
example, the results of such testing can provide a fairly accurate reflection of an
individual’s fitness status without the cost, risk, effort (on the part of the subject)
and time involved in max testing. If an individual is given repeated
7000 PT CONSOLE