25
Nautilus® Commercial Series Bike Owner’s Manual
graded exercise test. The U916 and R916 bikes use the most current published equation developed to
estimate the average maximal heart rate as follows:
Maximal heart rate = 215 minus (0.75 x age)
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 VO2 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 average oxygen consumption
associated with a given workload may vary significantly from one person to another. Thus, VO2 max
predicted by sub-maximal exercise tests tends to be overestimated for those who are mechanically
efficient and underestimated for those who are inefficient.
The point to remember is that sub-maximal 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 sub-maximal exercise tests and that
person’s heart rate response to a fixed workload is found to decrease over time, it is reasonably safe to
conclude that the individual has made improvements in aerobic (cardiorespiratory) fitness, irrespective
of the accuracy of the VO2 max prediction.
Pretest Screening
Prior to any exercise test (maximal or sub-maximal), participants should complete a brief health/
medical questionnaire, have their resting blood pressure and heart rate measured, and provide an
informed consent form. The Physical Activity Readiness Questionnaire (PAR-Q) is an example of a valid
health/medical questionnaire for screening individuals prior to sub-maximal exercise testing. Canadian
health and fitness practitioners have extensively (and quite successfully) used the PAR-Q to determine
whether individuals should be given an exercise test. A “yes” answer to any of the following seven
questions taken from the PAR-Q would disqualify a participant from taking part in an exercise test until
appropriate medical clearance was obtained.
Physical Activity Readiness Questionnaire (PAR-Q)
1. Has your doctor ever said you have a heart condition and recommended only medically supervised
physical activity?
2. Do you have chest pain brought on by physical activity?
THE NAUTILUS
®
FIT TEST PROGRAM