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Lecture 3

# PHTY209 Lecture Notes - Lecture 3: Vo2 Max, Cardiorespiratory Fitness, ExtrapolationExam

Department
Physiotherapy
Course Code
PHTY209
Professor
Lee Plumbe
Lecture
3

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Sub-maximal Physical Work Capacity testing for the prediction of VO2max
Participant _________ Age: 19 Mass: 56kg Height________
Background:
Cardiorespiratory fitness is a measure of how efficiently the heart, lungs and muscles work
together to keep the body functional over a period of time (Frey, 2017). This study was
designed to develop a sub-maximal physical work capacity test to predict the maximal
oxygen uptake (VO2max) of an adult participant. In this test VO2max was predicted thought
extrapolation of maximal heart rate (bpm) with maximal power (watts). Since heart rate is
directly proportional to power and VO2 max, and thus further accurately calculated using the
linear regression equation ( VO2max = 0.18 + (0.0134 * Wmax)
Heart rate is defined by “the amount of work the heart must do to meet the increased
demands of the body when engaging in activity" (Wilmore & Costill, 2004). In accordance
with Wilmore and Costill, heart rate is increases proportionally with the intensity of the
movement and the volume of oxygen consumed (VO2), where VO2 is the volume of oxygen
consumed per minute. This confirms that heart rate is directly proportional to VO2. The aim
of this report was to test the correlation between heart rate and VO2max by running the
participants thought series of work load and noting the changes in the heart rate. The aim was
confirmed as when there is an increase in power, there is an increase in heart rate which then
increases the Vo2 of the participant proportionally, as shown by the above graph.
Does a 2 min HR power relationship extrapolate to the same predicted VO2max as a 3
min HR power relationship. Ie is a plateau (equilibrium) HR reached at 2 mins of constant
content/9780781792073_Plowman/samples/Chapter_13_Cardiovascular_Respo
nses.pdf
- At the onset of short-term, light- to moderate-intensity exercise, there is an initial
increase in cardiac output (Q) to a plateau at steady state. Car- diac output
plateaus within the first 2 min of exercise, reflecting the fact that cardiac output is
sufficient to transport the oxygen needed to support the metabolic demands (ATP
production) of the activity. Cardiac out- put increases owing to an initial increase
in both stroke volume (SV) and heart rate (HR). Both variables level off within 2
min.
- During exercise of this intensity the cardiorespi- ratory system is able to meet the
metabolic demands of the body; thus, the term steady state, that is the exercise
is performed at an intensity such that energy expenditure is balanced with the
energy required to perform the exercise.

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- There is a linear relationship between heart rate, mechanical power output
and predicted VO2max.
- HR increases in proortion to power output until 85% of the velocity at
VO2max.
- The present study, substituting the maximal heart rate for that suggested by
Anderson et al (1971) for each age-group revealed no significantd ifference in
the extrapolated results.
- Neither VO2max nor HR increases linearly at high power outputs during
incremental exercise tetsing (Zoladz, Duda, & Majerczak, 1998)
https://pdfs.semanticscholar.org/73a6/4b1158963d557855f3dd574e80ca01b1
f0e8.pdf
- Refer to
3319056357-c2.pdf?SGWID=0-0-45-1499980-p176652143.
- Therefore, VO2 attained a steady level which can be maintained for a long
period of time.
- The steady-state oxygen consumption is proportional to the exerted
mechanical power.
- Once the steady state has been attained, the flow of oxygen is the same at all
levels along the respiratory system.