Stairmaster Crossrobics 1650 LE, Руководство пользователя

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Page 24
CROSSROBICS 1650 LE CONSOLE
150, external factors no longer influence heart rate, and a linear relationship
exists. As the heart rate rises above 150, the heart-rate/oxygen uptake rela-
tionship 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 exercis-
ing to the point of volitional fatigue (i.e., exhaustion) during a graded exercise
test. Several 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-
predicted 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.
Oxygen uptake at any given work rate can vary by approximately 15%
between different individuals. Therefore, 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 aver-
age oxygen consumption associated with a given workload may vary signifi-
cantly from one person to another. Thus, VO
2 max
predicted by submaximal exer-
cise tests tends to be overestimated for those who are mechanically efficient
and underestimated 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