A thorough critique of the Progressive Speed Protocol used for measuring maximal oxygen
uptake.
By Richard Brennan
INTRODUCTION
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Maximal oxygen uptake (VO2max) has been defined as ‘the maximal rate of oxygen consumption by
active muscle during exercise to fatigue’ (Mauger & Sculthorpe, 2011) and ‘the maximum rate at
which an individual can take up and utilize oxygen while breathing at sea level’ (Astrand et al., 2003).
VO2 max is also defined by the Fick equation: (left ventricular (LV) end-diastolic volume – LV endsystolic volume) x heart rate x atrio-venous oxygen difference.
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Since Hill & Lupton’s research in 1923 VO2max has been used as the ‘gold standard’ criterion
when measuring cardiorespiratory fitness. It has been described as ‘the single physiological variable
that best defines the functional capacity of the cardiovascular systems’ (Cooke, 2009). There is a
linear relationship between workload and oxygen intake up to a certain point. After this point
workload can usually be further increased but oxygen consumption does not increase but instead
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can level off or possibly decline (Mitchell et al., 1957). Since VO2 max can be increased with
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appropriate training it can be used as an indicator of training status. Information from VO2 max tests
can be used to design training programs or to assess the efficacy of an existing training program.
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In order to remove local muscular fatigue as a limiting factor it is recommended that VO2
max assessments are performed using large muscle groups. Treadmills, stationary bikes, rowers and
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swim flumes are examples of equipment used for VO2 max tests. However, when tested on a
treadmill subject have shown higher values than those attained on a stationary bike. The higher
.
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score is used as the more accurate VO2 max value (Beam & Adams, 2011). VO2 max tests directly
measure oxygen consumption, as well as respiratory exchange ratio, blood lactate, heart rate and
rating of perceived exertion although sometimes blood lactate testing is omitted in order for the test
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to be non-invasive. The VOmax2 test is considered to be valid, dependent on the fitness of the
subject and the modality used (Beam & Adams, 2011), and reliable with a test-retest reliablility of
0.95 (Taylor et al., 1955).
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The protocols used for VO2 max tests using a treadmill can be put into 2 distinct groups,
continuous and discontinuous tests. Both types of test normally involve incremental increases in
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work rate although a decremental protocol has also been shown to elicit a higher VO2 max in
subjects who have previously completed an incremental protocol (Beltrami et al., 2011).
Discontinuous tests may include short breaks for the subject to recover and for blood to be taken or
may involve stages with 2-3 days rest between (Duncan et al, 1996). Continuous tests, do not include
any breaks in work. Continuous treadmill protocols result in maximal physiological values (Duncan et
al, 1996). Within this subgroup of continuous tests exist protocols which differ in duration and
method of increment increase. Increases in work rate can be achieved by increasing treadmill incline
or treadmill speed or both.
The Test
THE PROGRESSIVE SPEED PROTOCOL (PSP).
The Progressive Speed Protocol (PSP) first described by Scrimgeour et al., (1986) then by
Matter et al., (1987), Noakes et al., (1990), Gibson et al., (1999) and Christie & Lock, (2009) is a
continuous, horizontal treadmill test which is usually completed by 10 minutes. The work rate is
increased by increments in the speed but not the incline of the treadmill. Previously reported
starting speeds have varied from 8km/h with increments of 0.5 km/h every 30 seconds, (Scrimgeour
et al, 1986) to 10 km/h with increments of 1km/h every minute, (Noakes et al., 1990) to 12km/h also
with increments of 1km/h every minute (Matter et al., 1987), (Gibson et al., 1999), (Christie & Lock,
2009). Subjects run until volitionally terminating the test, normally through exhaustion. Maksud and
Coutts (1971) found no significant difference between continuous and discontinuous exercise in
determining VO2 max and concluded by saying that a continuous test ‘…permits reasonably accurate
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measurement of max VO2 in group studies’.
Prior to the test the subject performs a warm-up. Various warm-ups have been used and
include running on the treadmill for 5 minutes at 8km/h then resting for 5 minutes (Scrimgeour et
al., 1986) or cycling for 5 minutes using a stationary cycle ergometer at an intensity decided by the
subject followed by stretching of the gastrocnemius, quadriceps and hamstring muscle groups
(Christie & Lock, 2009). No warm-ups were described by Matter et al., (1987), Noakes et al., (1990)
or Gibson et al., (1999).
Immediately before starting the test the subject is fitted with an air tight mask covering his
nose and mouth and a telemetric heart rate monitor. If the subject’s HR reaches a number within 10
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beats per minute of age-related maximum then a secondary determinant of VO2 max has been
reached BASES (1997). The subjects rating of perceived exertion (RPE) is recorded every 2 minutes
using the Borg 6-20 scale. Achieving 19-20 on the Borg scale is one of the secondary determinants of
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VO2 max as recommended by BASES (1997). Respiratory exchange ratio (RER) is also recorded as well
.
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as oxygen consumption (VO2). An R value over 1.15 satisfies a further criterion for VO2 max as does a
plateau in oxygen consumption as mentioned previously BASES (1997).
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CRITERIA FOR ACHIEVING VO2 MAX.
Source
O2 uptake plateau
Respiratory
exchange ratio
Blood lactate
Heart Rate
Rating of perceived
exertion
BASES
Australian Sports
Commission
Ex. Phys. Lab Manual –
Beam & Adams
Ex. Phys. Lab Manual –
Eston & Reilly
A plateau despite
increases in work
R value >1.10
5 min post exercise of
>8.0 mmol/L
N/A
N/A
A plateau despite
increase in power
R value >1.0
High blood lactates
Plateau of HR
No rating but state:
exhaustion
An increase in O2
uptake <2ml kg-1
min or 3%.
R value >1.15
4-5 min post exercise of
> 8.0 mmol/L
Within 10 beats
of age
predicted max
19 or 20.
Subjective fatigue &
volitional exhaustion
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Not all subjects display a plateau in when VO2 is graphed against work rate. It has been shown on
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more several occasions that about 50% of subjects who are close to VO2 max do not display a
plateau (Howley, Bassett and Welch, 1995). A subject may suffer fatigue or exhaustion, have an RPE
of 19-20 or have a heart rate within 10 beats per minute of maximum heart rate before a plateau is
.
evident even though the subject has reached VO2 max. It is because of this that Bassett & Howley
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(2000) state ‘…the plateau in VO2 cannot be used as the sole criterion for achievement of VO2 max.’
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Regardless of the protocol all VO2 max tests will be measuring the same physiological variables.
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Oxygen Consumption (VO2).
How much oxygen is being consumed by the body per minute. This is simply the difference between
the amount of oxygen being inhaled (VIO2) and the volume of oxygen being exhaled (VEO2). The
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calculation is expressed in L.min-1. This is known as absolute oxygen uptake. When VO2 max is being
used to express an individuals aerobic fitness it is expressed relative to body mass, mL.kg-1.min-1 this
is known as relative oxygen uptake. With short (around 10 minutes) continuous treadmill tests
metabolic gas analysis is usually undertaken using automated gas analysis systems such as the
Oxycon Pro, although the validity and reliability of such systems has been questioned (Rosdahl et al.,
2010).
Ventilation (VE). The total amount of air exhaled per minute. This measurement is initially expressed
as VE ATPS (ambient temperature pressure saturated) and must be transformed to VE STPD (standard
temperature pressure dry) in order to account for ambient conditions which clearly vary from one
laboratory or testing area to another. When using the Oxycon Pro software the ambient
temperature and pressure readings are entered before the test starts.
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Advice regarding the optimal duration for achieving true VO2 max readings, whilst using a
continuous protocol, varies and includes small and frequent workload increments (Myers and Bellin,
2000) a recommended test duration of around 10 minutes (Buchfuhrer et al, 1983), (Yoon et al.,
2007). These recommendations are substantially less than those protocols used in clinical practice
such as the Astrand test , Balke test and Bruce test. It is not unusual for these tests to last more than
20 minutes. Lukaski et al., (1989) found that certain step protocols, (Bruce and Ellestad) resulted in
greater oxygen debt and higher levels of blood lactate compared to the Balke protocol but that the
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Balke protocol resulted in a much longer test duration and lower VO2 max scores. Although these
protocols are still widely used there is a growing trend towards using more individualised ramp
protocols which include small but frequent increases in intensity as opposed to the step protocols
mentioned earlier, in fact Froelicher et al., (1975) state that, ‘We do not feel either (Bruce or Balke)
protocol is optimal for clinical usage.’ The American College of Sport Medicine, American Heart
Association and the American College of Cardiology all recommend individualising the test in order
to optimise exercise testing (Myers and Bellin, 2000).
Buchfuhrer et al., (1983) found that the optimal time for an individualised test was
approximately 10 minutes although this was a very small study of 6 subjects . A more recent study by
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Yoon et al., (2007) involving 16 subjects performing 4 different protocols concluded that ‘when
testing young, healthy, active individuals the protocol duration for VO2 max assessment should be
between 8-10 minutes’. This has been further supported by Mauger & Sculthorpe (2011) who
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proposed a ‘self-pacing’ protocol timed to last 10 minutes and found that this elicited higher VO2
max readings than traditional methods. In a comparison of ramp versus standard protocols Myers et
al., (1991) also recommend a test duration of 10 minutes and concluded by saying ‘maximal oxygen
uptake is more accurately predicted using protocols with shorter and smaller work increments’. One
drawback of individualising ramp protocols however is some knowledge of the subject’s capacity for
exercise is required although this can be gained through a self-administered questionnaire (Myers &
Bellin, 2000).
Gibson et al., (1979) reported work capacity being limited by discomfort caused by the mouthpiece.
They also found that the latter stages of the Bruce protocol caused localised muscle fatigue in the
legs due to the treadmill incline. Their recommendations for treadmill testing included an initial
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warm-up of at least 5 minutes at 50% VO2 max and that either the grade or the speed be increased
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but not both. Freund et al., (1986) found that there was no difference in VO2 max values between
different tests when comparing inclined protocols and horizontal protocols although their subjects
were experienced runners. Previous research by Taylor et al., (1955) suggests that an inclined
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protocol will achieve a higher VO2 max but this was using untrained subjects.
Figure 1. (Gibson et al., 1998)
This illustrates the readings from 4 subject who either
did or did not reach a plateau near the end of their
treadmill test. Interestingly the Progressive Incline
Plateau lasts almost 3 times as long than the
Progressive Speed Protocol.
When comparing test results over time it is important that the same protocol has been used (Myers
& Bellin, 2000). One disadvantage is, unlike the Bruce protocol for example, the paucity of data on
the PSP. This means judging the starting speed may be difficult. In order to overcome this a
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questionnaire such as The Huet Questionnaire (Trivel et al., 2004) may be used to predict VO2 max
and then a starting speed can be suggested based on the result.
Summary
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The Progressive Speed Protocol (PSP) can directly measure VO2 max. By increasing the work rate
gradually every minute until either exhaustion, an R value >1.0, an RPE rating of 19 or a plateau in
O2 consumption has been achieved a subjects capacity for aerobic work can be measured quickly
and non-invasively.
Practical Application




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
Complete relevant paperwork.
Calibrate the gas analyser.
Make sure the treadmill is horizontal using a spirit level.
Explain the RPE Borg Scale and its use correctly before the test starts.
Explain how the emergency stop works.
Wear the heart rate monitor during the warm-up. This will ensure it is
working and if not that it can be changed before the test starts.
 Warm-up for 5 minutes prior to the test at an intensity of approximately
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50% of their predicted VO2 max.
 Jump around with the mask fitted to see if any movement occurs as
expired air can be lost through a poor fitting mask.
 Encourage the subject verbally toward the end.
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