User's Manual

Chapter 9 - Sub-maximal Exercise Testing - 107
Sub-maximal exercise testing
Heart rate varies linearly with VO
2
to the point of maximum exertion; thus, VO
2max
may
be estimated using the relation between heart rate and VO
2
without subjecting the
individual to maximum levels of physical stress. During sub-maximal exercise testing,
predetermined workloads are used to elicit a steady state of exertion (plateau of heart
rate and VO
2
). The steady-state heart rate at each work level is displayed graphically
and extrapolated to the VO
2
at the age-predicted maximal heart rate (HR = 220-age). A
variety of protocols for different exercise modalities (i.e., treadmill, stationary cycle,
and step increments) can be used as long as the VO
2
requirements of each selected
workload can be estimated with accuracy.
The objectives of cardiorespiratory fitness assessments in the apparently healthy
population are as follows:
• Determine the level of cardiorespiratory fitness and establish fitness program goals
and objectives.
• Develop a safe, effective exercise prescription for the improvement of
cardiorespiratory fitness.
• Document improvements in cardiorespiratory fitness as a result of exercise training
or other interventions.
• Motivate individuals to initiate an exercise program or comply with an established
program.
• Provide information concerning health status.
A few assumptions regarding testing are necessary to ensure the highest degree of
accuracy when using sub-maximal exercise testing to estimate VO
2max
:
• Selected workloads are reproducible. A steady-state heart rate is obtained during
each stage of the test. Usually, workload durations of 3 minutes or more are used to
ensure steady state.
• The maximal heart rate for a given age is uniform (HR = 220-age).
• Heart rate and VO
2
have a linear relation over a wide range of values; thus, the
slope of HR/VO
2
regression can be extrapolated to an assumed maximum heart
rate.
• Mechanical efficiency (i.e., VO
2
at a given work rate) is consistent.
Although if done correctly, sub-maximal exercise tests provide valuable information
concerning cardiorespiratory fitness, they have extremely limited diagnostic capabilities
and should not be used as a replacement for clinical exercise tests or other clinical
treatment or management modalities. Health care professionals should avoid detailed
interpretation beyond the scope of the information obtained.
Considerations with sub-maximal exercise testing
Considerations for selection of protocol and equipment include any physical or clinical
limitations that may preclude certain types of exercise (i.e., age, weight, arthritis,
orthopaedic complications, individual comfort, level of fitness, type of exercise training
that will be performed, and individual preference).
For example, some individuals may perform better on a non-weight-bearing modality
(cycle versus treadmill), while others may not have the required range of motion in the
hip or knee to pedal and may perform better walking. Deconditioned, weak, or elderly
persons may have to start the test at a low work level and increase the workload in small
increments. Also, field tests may not be appropriate for those who require strict
supervision during testing, who do not understand the concept of pacing, or who cannot
be expected to put forth a good effort. More consistent results may be obtained by
testing in a controlled environment such as a laboratory setting. Creativity when
selecting protocols may allow adaptations of commonly used protocols to accommodate
athletes competing in specific sports. Regardless of the type of exercise and protocol
selected, the same type of exercise and protocol should be used for repeat testing if
between-test comparisons are important.