Submaximal Exercise Testing

 

Objectives for Laboratory 7

• Reinforce the terminology and techniques associated with measuring blood pressure at rest and during exercise.
• Learn the skills needed for administering two types of submaximal exercise tests.
• Reinforce the terminology and techniques associated with measuring heart rate at rest and during exercise.
• Estimate VO2max by the measure of HR response to submaximal exercise.

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Submaximal Exercise Testing

Knowing a subject's cardiorespiratory capacity, or VO2max, can be useful for exercise prescription or diagnostic purposes in at-risk populations. Tests for estimating VO2max can be maximal (i.e., involving incremental workloads to the point of failure; see the following laboratory) or submaximal (i.e., ending before extreme exertion). Submaximal estimates of cardiorespiratory capacity can be more practical because they do not require expensive automated metabolic laboratory equipment and trained personnel. However, they do require some knowledge and skill to carry them out properly. Many submaximal tests exist, and they differ by target population, duration, and modality (e.g., bikes, treadmills). Depending on the submaximal tests protocol, you may be required to monitor HR (heart rate), BP (blood pressure), patient symptoms, time, ergometer work rates, and Rate of Perceived Exertion (RPE). The most important one for this Laboratory activity will be monitoring HR.

 

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 The Relationship between Heart Rate and Oxygen Consumption

In non-disabled individuals, heart rate and oxygen uptake have a linear relation up to submaximal workloads. The figure below shows the outputs obtained from a VO2max test. Notice how closely related exercise responses are between VO2 (red line) and HR (purple line). This relationship motivates the great interest that field exercise professionals have in monitoring HR responses during exercise. During a submaximal exercise test, it is possible to estimate the VO2 max using submaximal HR responses.

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Measurement of Heart Rate

Heart Rate (HR) during exercise can be measured by palpation, auscultation, ECG, and wearable technology (e.g., heart rate monitor, smartwatches). 

As you will practice in this lab, measuring HR by palpation is a free and vital—literally—skill that exercise professionals must master. 

HR can be palpated at several sites, including the radial, brachial, carotid, temporal, and femoral arteries. This is relatively easy to do when the subject is at rest but can be challenging during exercise due to extraneous noise. Therefore, the radial, carotid, and temporal sites are preferred during exercise. While the carotid and temporal sites are ideal for self-palpation of the heart rate, the radial site is the most appropriate when monitoring a subject's heart rate. After detecting the pulse in one of the sites shown in the figure below, with a stopwatch, count the number of beats over 6, 10, or 15 s and multiply the number of beats by 10, 6, or 4, respectively, to extrapolate the average number of beats per minute. Assessing HR during longer intervals yields greater accuracy. In the example below, the participant's pulse count measurements were taken within the same time window. Results showed that pulse cont was 5 after a 6-second count, 9 after a 10-second count, and 13 after a 15-second count. When extrapolating these pulse counts to beats per minute (bpm), which is the unit used to report the heart rate, the estimated heart rate were 60 bpm for the 6-second count, 55 bpm after the 10-second count, and 52 bpm after the 15-second count. It is important to note that although measurements were taken within the same time window, HR was slightly different between conditions.