Hello, welcome back to Training Course One. This is Lesson Five: Calculations from a Fitness Test.
The learning objectives for this lesson are to understand the different outcomes that can be measured or predicted from a fitness test, to learn how to calculate predicted peak oxygen capacity from treadmill and shuttle tests, and to learn how to use fitness test results to compare across tests, compare with normative data, determine capacity to return to pre‑injury activities, and set global participation‑level goals with supporting sub‑goals.
There are a number of different variables that can be measured or predicted from a fitness test. The first is measured oxygen capacity. This requires the use of gas analysis equipment, such as a portable system like the Cosmed device shown here. This type of measurement is not standard or required in clinical settings and is more commonly used in research. When gas analysis is used, it provides a true measured value of oxygen capacity. In the example shown, the measured value was 35.04 millilitres per kilogram per minute.
When oxygen capacity is measured directly, the value used is typically the average of the final 20 seconds of the last completed level. Measured testing also allows clinicians to determine whether the value represents a true maximal VO₂ or a peak VO₂. To be considered a true maximal VO₂, several criteria must be met. The respiratory exchange ratio must exceed 1.15, the maximum heart rate must be within 15 beats of the predicted maximum, the change in VO₂ between the final two stages must be less than 150 millilitres, and systolic blood pressure must exceed 200 mmHg. If all four criteria are met, the test reflects a true maximal VO₂; otherwise, the value is considered a peak VO₂. This distinction is typically relevant in research rather than routine clinical care.
In clinical settings, a fitness test usually provides other useful measures. These include measured submaximal or peak heart rate, measured workload such as watts, speed, incline, and total test duration, as well as ratings of perceived exertion using Borg scales. For example, during a treadmill test, you might record that the test lasted 11 minutes, reached a maximum speed of 8.5 km/h at a 15% incline, and achieved a peak heart rate of 188 beats per minute. This heart rate can then be expressed as a percentage of predicted maximum. Perceived exertion can also be documented, such as a rating of 5 on the Borg scale, which corresponds to “strong” exertion.
In addition to these measured outcomes, predicted peak VO₂ can be calculated using equations. The American College of Sports Medicine provides standardized equations, but many of these are not accurate for individuals with traumatic brain injury. For this reason, equations that have been specifically developed and validated in TBI populations should be used.
For the modified shuttle test, a validated equation is available. Predicted VO₂ peak is calculated as 4.12 multiplied by velocity maximum, minus 0.19. Velocity maximum is determined by the speed of the last completed level, adjusted based on the number of shuttles completed in the final level. This calculation has been built into the Bridges Fitness Training worksheet, allowing clinicians to input test values and automatically obtain the predicted VO₂ peak. A worked example is provided using a flip‑card format to allow self‑checking.
A similar approach applies to treadmill testing. A validated equation has been developed specifically for individuals with TBI using the individualized treadmill protocol discussed in the previous lesson. This calculation is more complex and incorporates the standardized ACSM treadmill equation. It requires knowing whether the participant was walking or jogging, whether they were holding onto the handrails, and the exact speed and incline achieved. This reinforces the importance of recording these variables during testing. The treadmill calculation is also built into the Bridges Fitness Training worksheet, with worked examples available.
Fitness test results can also be graphed to illustrate changes in fitness over time. The training worksheet includes a graphing function where values from two tests can be entered and automatically plotted. For example, shuttle test results collected four weeks apart may show a lower resting heart rate, lower heart rate at each level, and greater test duration, all indicating improved fitness.
Predicted VO₂ peak values can also be compared with normative data to determine how an individual compares with age‑ and sex‑matched populations. Normative values from the ACSM are included in the Bridges Fitness Training worksheet, allowing clinicians to identify percentile rankings. Worked examples are again provided to support learning.
Fitness test results can also be used to assess capacity to return to pre‑injury work and leisure activities. This involves referencing the Compendium of Physical Activity, which provides estimated MET values for a wide range of activities. For example, walking the dog has a MET value of 3, raking leaves has a MET value of 4, and playing basketball has a MET value of approximately 7.5.
To interpret this information, predicted VO₂ peak can be converted to METs by dividing by 3.5. For example, a predicted peak oxygen uptake of 31.5 millilitres per kilogram per minute equates to approximately 9 METs. This allows clinicians to determine whether an individual has sufficient aerobic capacity to safely and sustainably return to specific activities. Additional worked examples are provided using the training worksheet and Compendium resources.
Finally, fitness test results can support goal setting at the global and participation levels. Using MET values from the Compendium helps quantify the fitness required for meaningful life activities. This approach is particularly useful when justifying funding for fitness training interventions through insurance schemes or NDIS rehabilitation plans.
For example, a team‑based global goal may be for an individual to return to independently caring for her children. A supporting physiotherapy or exercise physiology goal might be to increase aerobic fitness to a good normative level, such as 31 millilitres per kilogram per minute or approximately 8.9 METs, depending on age. This level would allow her to participate in activities such as playing with her children, which has an estimated MET value of 5.8, without excessive fatigue. These quantified outcomes help clearly justify the inclusion of structured fitness training in rehabilitation.
This concludes Lesson Five. Please complete the quiz. Thank you.
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