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The Nautilus
®
Fit Test Program
Understanding Sub-maximal Exercise Testing
Before using the Nautilus
®
U916 or R916 bike for sub-maximal exercise testing, it should be noted that all
sub-maximal tests make several assumptions:
• That a steady-state heart rate is obtained for each exercise workload.
• That a linear relationship exists between heart rate, oxygen uptake and workload.
• That the maximal heart rate for a given age is uniform.
• That the mechanical efficiency of the physical activity performed (i.e., oxygen uptake at a given
workload) is the same for everyone.
It should be kept in mind that any one or all of the above mentioned assumptions may not be met during a
sub-maximal exercise test. If for any reason one of the assumptions is not met, then errors in predicting
VO2 max will occur.
Unfortunately, it is often quite difficult to meet all of the requirements for the four listed assumptions.
For example, exercising at a given workload for only a few minutes can involve an insufficient amount
of time for many individuals to achieve a true steady-state. To ensure that a steady-state has been
achieved, the heart rate should be measured after two minutes of exercise at a given workload and
again after the third minute of exercise at that workload. These two heart rates should then be
compared. If a difference of more than five beats per minute between the two is found, the subject
should continue to exercise at one-minute intervals at the same workload until two successive heart
rates differ by less than five beats per minute.
It is also important that the sub-maximal heart rates obtained be between 115 and 150 beats per minute,
because it is within this heart rate range that a linear relationship tends to exist between heart rate and
oxygen uptake or workload for most adults. When the heart rate is less than 115, many external factors
(e.g., talking, laughing, apprehension, etc.) can greatly influence heart rate. Once the heart rate reaches
a level between 115 and 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 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
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