Download Quantity and Quality Position Stand

Quantity and Quality Position Stand
Section 3. Cardiorespiratory Fitness (Swain)
3.1. Volume of Exercise
The total volume of exercise performed on a weekly basis is the product of
intensity x duration (per session) x frequency (sessions per week). This can be translated
into energy expenditure (EE), i.e., kcal.wk-1. The volume of exercise should be indicated
in terms of net EE, not gross. For example, a 70-kg person expends approximately 1.2
kcal.min-1 for resting EE, and when walking at 4.8 kph (3.0 mph) expends an additional
2.8 kcal.min-1 (based on the ACSM metabolic equation for walking).(ACSM GETP8, in
press) If the person walked for 30 min per day, 5 days per week, the net EE caused by the
walking would be 84 kcal per session or 420 kcal.wk-1. An additional 36 kcal would be
expended per 30-min session for on-going resting metabolism, which would have
occurred even if the person had not exercised. Thus, it is essential that net EE be used
when determining expected weight loss associated with exercise.
The ACSM and AHA have recently recommended that healthy adults engage in
moderate intensity aerobic activity for at least 30 min on 5 days per week, or vigorous
intensity aerobic activity for at least 20 min on 3 days per week, or a combination of
moderate and vigorous intensity activities 3-5 days per week.(Haskell et al., 2007) A
target volume recommendation from the U.S. Surgeon General’s office and the ACSM is
a minimum of 1,000 kcal.wk-1.(SG report, 1996; ACSM GETP8, in press) However,
Church et al. (2007) reported that individuals with low baseline fitness (16 mL.min-1.kg-1,
or 4.6 METs) experienced improvements in aerobic capacity (VO2max), with exercise
volumes as low as one third of this weekly target, obtained by walking 72 min per week.
In general, greater volume of exercise will result in greater benefits.(SG report,
1996) In Church et al.’s study, greater increases in aerobic capacity were obtained when
volume was raised from approximately 330 to 840 kcal.wk-1, and to 1,000 kcal.wk-1 (4%,
8% and 12%, respectively).(Church et al., 2007) However, a separate study using
subjects with a higher baseline fitness (30 mL.min-1.kg-1, or 8.6 METs) found that 1,000
kcal.wk-1 and 1,500 kcal.wk-1 both resulted in an 8% increase in VO2max.(Asikainen et al.,
2003) While volume of exercise plays a role in increasing aerobic capacity, the intensity
component of the exercise dose has a greater impact on improving VO2max (see below).
Beyond aerobic capacity, greater volume of training clearly leads to greater fat
loss,(Slentz et al., 2004) as expected based on energy balance.
The maximum appropriate volume of exercise is not known. For successful longterm weight loss, a minimum of 2,000 kcal.wk-1 is recommended,(Jakicic et al., 2001
ACSM position stand) requiring 60-90 min per day of moderate intensity
activity.(Weinsier et al., 2002) In the Tour de France, elite athletes expend approximately
4,000 kcal.d-1 during exercise over the course of three weeks, for a net EE of 28,000
kcal.wk-1, with no apparent ill effects.(Saris et al., 1989)
In conclusion, a minimum goal of 1,000 kcal.wk-1 is appropriate for most adults,
although lower volumes are initially effective with deconditioned individuals. To
optimize fitness and health benefits while minimizing the risk of overtraining and
orthopedic stress, average adults are encouraged to gradually increase weekly volume
until weight loss and fitness goals are reached, which may occur in the range of 2,0004,000 kcal.wk-1.(ACSM GETP8, in press) Greater volume may be considered on an
individual basis.
3.2. Intensity of Exercise
Intensity of aerobic exercise is best indicated relative to one’s capacity,
specifically as a percentage of the difference between resting and maximum oxygen
consumption (%VO2 reserve, or %VO2R) or as the same percentage of the difference
between resting and maximum heart rate (% heart rate reserve, or %HRR). Light
intensity is defined as < 40% VO2R or HRR, moderate intensity as 40-59% VO2R or
HRR, vigorous intensity as 60-84% VO2R or HRR, and near-maximal intensity as 85100% VO2R or HRR (Table 1). Other relative means of assigning intensity are
percentage of maximum heart rate (HRmax), percentage of maximum oxygen consumption
(%VO2max) and ratings of perceived exertion. Intensity may also be prescribed as an
absolute workload (e.g., speed and grade on a treadmill, power on an ergometer) or as
METs.
3.2.1. Threshold Intensity
According to the overload principle of training, exercise at too low of an intensity
will not challenge the cardiorespiratory system sufficiently to result in increased aerobic
capacity. The minimum intensity that elicits a training induced increase in aerobic
capacity is known as the threshold. In Karvonen et al.’s classic study, it was reported that
young men must exercise at an intensity of at least 70% HRR to improve
cardiorespiratory fitness.(Karvonen et al., 1957) In a comprehensive review, Swain and
Franklin (2002) evaluated 18 clinical trials that measured pre and post VO2max in 37
training groups, and found that subjects with mean baseline VO2max values of 40-51
mL.min-1.kg-1 (11-14 METs) required an intensity of at least 45% VO2R to increase
VO2max. No threshold was found for subjects with mean baseline capacities < 40 mL.min1.
kg-1 (< 11 METs), with ~30% VO2R being the lowest intensity studied. Recent clinical
trials with higher fit subjects (mean VO2max = 52-60 mL.min-1.kg-1, 15-17 METs)
obtained no increase in VO2max using 72-75 %VO2R, but did increase VO2max using
interval training at 85-100% VO2R.( Esfarjani & Laursen, 2007; Helgerud et al., 2007)
As one’s genetic potential is approached, it becomes increasing difficult to further raise
VO2max. Studies of runners with mean baseline VO2max values of 62 and 71 mL.min-1.kg-1
obtained little to no increase, respectively, in VO2max using interval training at
VO2max.(Smith et al., 1999; Billat et al., 1999)
Given that the threshold intensity rises with baseline fitness, recommended
minimum intensities for increasing VO2max are 30% VO2R for adults of low to average
fitness (< 11 METs), 45% VO2R for moderately fit adults (11-14 METs), and 85% VO2R
for highly fit adults (> 14 METs). Exercise for weight loss does not need to reach these
threshold intensities. Nor have threshold intensities been established for other potential
benefits of exercise, such as reduced resting blood pressure and improved insulin
sensitivity.
3.2.2. Value of Higher Intensities
Threshold intensities are the minimum effective level for increasing VO2max.
Additionally, intensities above threshold vary in their effectiveness. Among the
components of an exercise prescription (frequency, duration, intensity and volume),
intensity has the greatest influence on raising VO2max. Swain and Franklin’s review
revealed that, when volume of exercise is held constant, training at vigorous intensities
resulted in greater increases in aerobic capacity than training at moderate
intensities.(Swain and Franklin, 2002). This is illustrated in Figure 1.(Swain, 2005) Since
Swain and Franklin’s review, 11 additional clinical trials have compared the effects of
training at two or more intensities with volume held constant (Table 2). Eight of the 11
studies found significantly greater increases in VO2max in the higher intensity groups. The
most recent study, by Gormley et al., compared moderate (50% VO2R), vigorous (75%
VO2R) and near-maximal intensity (95% VO2R), and obtained increases in VO2max of
10%, 14% and 21%, respectively.(Gormley et al., submitted)
The use of interval training was once restricted to athletes. However, recent
studies have successfully used such training with average young adults,(Gormley et al.,
submitted) relatively fit young men,(Helgerud et al., 2007) older men and
women,(Nemeto et al., 2007) middle-aged male cardiac patients,(Warburton et al., 2005)
older male and female cardiac patients,(Rognmo et al., 2004) and elderly heart failure
patients.(Wisloff et al., 2007) Interval training is typically performed at near-maximal
intensity (90-100% VO2R) in bouts of 2-5 min, separated by bouts of equal duration at a
light to moderate intensity. Usually, 4-6 intervals are performed in a single training
session, and 2-3 sessions are performed per week. Depending on the mode of exercise,
high intensity interval training entails added orthopedic stress, and is typically performed
for only 4-6 weeks at a time, although it has been successfully used for as long as 12-16
weeks.(Warburton et al., 2005; Wisloff et al., 2007)
The ACSM and AHA currently recommend that one means of attaining sufficient
aerobic exercise is to combine moderate intensity and vigorous intensity sessions for a
total of 3-5 sessions per week.(Haskell et al., 2007) Two recent clinical trials have
studied combination training with total volume controlled. One compared training at a
moderate intensity, 5 days per week, with combination training consisting of moderate
intensity exercise 3 day per week and near-maximal interval training 2 days per
week,(Warburton et al., 2005) while the other compared 4 days per week of vigorous
intensity exercise with combination training consisting of vigorous intensity exercise 2
days per week and maximal intensity interval training 2 days per week.(Esfarjani and
Laursen, 2007) Both studies obtained greater improvements in fitness in the combination
group. To date, no studies have evaluated the combination of moderate and vigorous
intensity training sessions. However, the evidence that vigorous intensity training
provides greater benefits than moderate intensity training, and the evidence that
combinations of near-maximal intensity sessions with either moderate or vigorous
intensity sessions provides greater benefits than either intensity of continuous training
alone, supports the use of combination training in general.
Intensity has an apparent impact on additional health-related benefits of exercise.
In 2006, Swain and Franklin reviewed both epidemiological studies and clinical trials in
which intensity was varied while volume was controlled.(Swain and Franklin, 2006)
Epidemiological studies revealed lower incidence of heart disease and lower risk factors
(blood pressure, insulin resistance, dyslipidemia) with higher intensities of physical
activity, while clinical trials revealed greater increases in aerobic capacity and suggested
greater improvements in blood pressure and insulin resistance. The most recent clinical
trials presented in Table 2, only two of which were included in Swain and Franklin’s
review,(Asikainen et al., 2003; Kang et al., 2002) found that higher intensities of exercise
were better than lower intensities at decreasing blood pressure,(Asikainen et al., 2003;
Kang et al., 2002; Nemeto et al., 2007) improving indices of blood glucose
control,(Asikainen et al., 2003; DiPietro et al., 2006) decreasing LDLcholesterol,(O’Donovan et al., 2005) increasing LDL particle size,(Kang et al., 2002) and
improving left ventricular function.(Wisloff et al., 2007) Additional studies are warranted
to further elucidate the role of exercise intensity in improving health-related study endpoints.
3.2.3. Percent Oxygen Consumption Reserve (%VO2R)
In its 1998 position stand, the ACSM adopted VO2 reserve as the primary means
of assigning aerobic exercise intensity.(Pollock et al., 1998) The use of %VO2R has
several advantages over %VO2max. %VO2R has a one-to-one relationship with %HRR,
providing an accurate means of translating intensity into a heart rate prescription.(Swain
and Leutholtz, 1997) There is a discrepancy between %VO2max units and %HRR units
that is larger in low fit clients than higher fit clients, and larger at lower intensities than
higher intensities.(Swain and Leutholtz, 1997) The close relationship of %VO2R and
%HRR has been confirmed in a large variety of populations, including young adults
engaged in stationary cycling,(Swain and Leutholtz, 1997) treadmill exercise(Swain et
al., 1998) and elliptical exercise,(Dalleck and Kravitz, 2006) cardiac patients with or
without beta-blocker medication,(Brawner et al., 2002) diabetic patients with or without
autonomic neuropathy,(Colberg et al., 2003) obese individuals,(Byrne and Hills, 2002)
and elite competitive bicyclists.(Lounana et al., 2007)
A second advantage of %VO2R is that it places clients with different levels of
baseline fitness at the same relative intensity, while %VO2max does not. Consider a
prescribed intensity of 40% VO2max in three clients, one deconditioned (5 MET capacity,
or 17.5 mL.min-1.kg-1), one average (10 METs; 35 mL.min-1.kg-1) and one highly trained
(20 METs; 70 mL.min-1.kg-1). An intensity of 40% VO2max yields target VO2s of 7.0, 14.0
and 28.0 mL.min-1.kg-1, respectively. As percentages of VO2R, these translate to 25%,
33% and 37%, respectively. Therefore, when prescribed a given intensity based on
%VO2max, the deconditioned client would be asked to use a much smaller portion of his
or her exercise capacity than the other clients.
A third advantage of using %VO2R is that it directly relates to workload and net
EE, while %VO2max does not. In the example above, 40% of VO2max is 25% of VO2R for
the deconditioned client, and would also be 25% of maximal workload. If 40% of VO2R
were prescribed, all three clients would be at 40% of their respective maximal workloads.
To prescribe exercise using %VO2R, the desired intensity (e.g., moderate is 4059% VO2R) must be translated to a target HR using either %HRR (preferred) or %HRmax,
or a target workload based on the ACSM metabolic equations or MET tables, or an
indicator of perceived exertion, as discussed below.
3.2.4. Percent Heart Rate Reserve (%HRR)
The %HRR method is the most accurate means of assigning a target HR. This is
because of its close relationship with %VO2R, and because it accounts for variations in
clients’ resting HR, while the %HRmax method does not. For example, consider two
clients who have the same maximal HR of 160 bpm but have resting HRs of 55 and 85
bpm. If both are placed at an intensity of 64% HRmax, they would both be instructed to
exercise at 102 bpm. However the client with the lower resting HR would be raising his
HR by 47 bpm (to 45% of HRR or VO2R), while the other raises his HR by only 17 bpm
(to 23% of HRR or VO2R). Using the %HRmax method, the relative intensity would be
twice as great for the client with the lower resting HR.
Resting HR should be measured after at least 5 min of quiet rest, preferably in the
position to be used during exercise, such as seated for stationary cycling. Maximum HR
should be obtained from an incremental exercise test. Otherwise, it may be estimated
using the Tanaka et al. equation: HRmax = 208 – 0.7(age in years). This equation was
established in a large cross-sectional study,(Tanaka et al., 2001) and a nearly identical
equation has been confirmed longitudinally.(Gellish et al., 2007) The well-known
formula of 220 – age may still be used for simplicity, but the Tanaka equation is more
accurate, especially for older clients, and is thus preferred. Regardless of which equation
is used to estimated HRmax, one must recognize that true HRmax varies widely among
individuals of a given age, thus the resulting target HRs are also only estimates.
Target HR with the %HRR method is calculated with the Karvonen
equation:(Karvonen et al., 1957)
Target HR = (intensity fraction)(HRmax – HRrest) + HRrest
where the intensity fraction is selected from the percentages provided in Table 1.
3.2.5. Percent Heart Rate Maximum (%HRmax)
As mentioned above, the %HRmax method is not as accurate as the %HRR method
for prescribing target HRs. However, it is useful when working with clients in a group
setting. There is a significant discrepancy between units of %HRmax and units of %VO2R
or %HRR. %HRmax values must be adjusted upward (see Table 1) to provide comparable
intensities.(Howley, 2001; Swain and Franklin, 2002).
3.2.5. Workload
%VO2R may be translated to a workload, such as a speed and grade on a treadmill
or a power output on a cycle ergometer, using the ACSM metabolic equations.(ACSM
GETP8, in press) First, the target VO2 would be determined from a modified Karvonen
equation:
Target VO2 = (intensity fraction)(VO2max – VO2rest) + VO2rest
where the intensity fraction is selected from Table 1; VO2rest may be estimated as
3.5 mL.min-1.kg-1.
An alternative means of establishing a target workload is to collect workload and VO2
data during an incremental exercise test, and identify the workload associated with the
desired VO2.
3.2.6. Metabolic Equivalents (METs)
A compendium of approximate MET levels for a variety of physical activities can
be used to prescribe exercise intensity.(Ainsworth et al., 2000)These MET levels are
rough values, and are influenced by the relative effort a client may choose to exert, and
by the client’s skill for many of the activities. To use the compendium, the target VO2
derived from %VO2R can be converted to a MET value by dividing VO2 in mL.min-1.kg-1
by 3.5. Alternatively, VO2max can be converted to a MET level, and the target MET level
calculated with a modified Karvonen equation:
Target MET level = (intensity fraction)(METmax – 1) + 1
The MET is based on the average VO2 during seated, casual rest, which is
approximately 3.5 ml.min-1.kg-1.(Swain and Leutholtz, 1997; Swain et al., 1998; Howley,
2000). Supine rest following a 12-hr fast is lower.(Byrne et al., 2005) Further, resting
VO2 expressed relative to body mass is lower in individuals with more, versus less, body
fat.(Byrne et al., 2005) Despite these points, the MET should continue to be defined as
3.5 ml.min-1.kg-1, because values in the compendium are derived as VO2 measured in
ml.min-1.kg-1 divided by 3.5 ml.min-1.kg-1 per MET, and are not based on multiples of
actual resting VO2 in different individuals.(Ainsworth et al., 2000) For a client prescribed
exercise using the compendium, a small difference between true resting VO2 and 3.5
ml.min-1.kg-1 is not multiplied when at higher MET levels, but remains a small difference.
3.2.7. Percent Maximal Oxygen Consumption (%VO2max)
As discussed above, the %VO2max method of prescribing exercise intensity is
less preferred than the %VO2R method, because %VO2max does not match up well with
%HRR, does not provide consistent relative intensities for clients with varying levels of
baseline fitness, and does not correlate as readily with workload and net EE. Nonetheless,
the %VO2max method is often used to prescribe exercise intensity, and is a valid means as
long as the noted limitations are taken into consideration. To use the %VO2max method,
Table 1 should be consulted to obtain appropriate intensities for clients of varying fitness.
To convert the VO2 obtained from %VO2max into a practical means of monitoring
exercise intensity, a workload or HR must be calculated. This can be done from the
information in Table 1, or can be done directly from workload or HR data collected
during an incremental exercise test.
3.2.8. Perceived Exertion
Clients may be taught to subjectively regulate their intensity through a variety of
methods, including the talk test and various scales for rating one’s perceived level of
exertion.
The talk test can establish a moderate exercise intensity. The client is asked to
work at a level that causes a sensation of increased breathing, but that still allows
comfortable speaking in complete sentences. When asked “Can you still speak
comfortably?”, answering “yes” is consistently associated with an intensity below the
ventilatory threshold.(Persinger et al., 2004) The intensity when a client provides an
equivocal answer is approximately at the ventilatory threshold, while intensities at which
the client says “no” are above the ventilatory threshold.
Among rating of perceived exertion (RPE) scales, the original, 6-20 Borg scale is
mostly widely used,(Borg, 1974) although a “category-ratio” Borg scale is also
available.(Noble et al., 1983) The OMNI scale has been recently reported,(Robertson et
al., 2004; Utter et al., 2004) which uses pictures illustrating varying levels of exertion
along with short descriptors and numbers from 0 to 10. The Borg scales(Borg, 1974;
Noble et al., 1983) and OMNI scale(Irving et al., 2006; Robertson et al., 2004; Utter et
al., 2004) have been validated against physiological measures such as VO2, HR and
lactate concentration during incremental exercise. However, when a client is asked to
report increasing numbers on a scale as the intensity of exercise is increased, strong
correlations with physiological measures that also increase must occur. Research is
needed to determine whether these scales can place a client at a desired intensity during a
prescribed exercise session. To maximize the utility of these scales, clients should be
familiarized with them during an incremental exercise test, and the levels corresponding
to desired exercise intensity pointed out.
3.3. Duration and Frequency of Exercise
As noted earlier, the volume of exercise per week is the product of intensity x
duration (per session) x frequency (sessions per week). Increases in one or more of these
factors produce increases in volume and, as noted previously, greater volume of exercise
leads to greater benefits. In its 1998 position stand, the ACSM provided a thorough
review of past studies leading to the recommendations of 20-60 minutes for exercise
duration and 3-5 sessions per week for exercise frequency for average adults.(Pollock et
al., 1998) Greater volumes are needed for long-term weight loss.
With intensity controlled, various combinations of session duration and session
frequency can be used to produce a given volume. Few clinical trials have examined
possible differential effects of varying duration and frequency while keeping volume
constant. One study compared 15 weekly bouts of 10-min duration versus 5 weekly bouts
of 30-min duration, and found that both regimens increased VO2max by ~8%.(Murphy and
Hardman, 1998) Another study using the same regimens found similar improvements in
HDL- and total-cholesterol between groups.(Murphy et al., 2002) One study compared 5
weekly bouts of 40-min duration with 20 weekly bouts of 10-min duration, and obtained
similar decreases in body mass and increases in cardiorespiratory fitness.(Jakicic et al.,
1999) Finally, a study compared 10 weekly bouts of 150 kcal per session with 5 weekly
bouts of 300 kcal per session, and found that VO2max increased similarly in both groups,
and that diastolic blood pressure, fasting glucose and body weight decreased similarly in
both groups.(Asikainen et al., 2003) Therefore, within the range of duration and
frequency combinations that have been examined, there appears to be no differential
effect on health-related training adaptations, and the use of multiple short bouts of
aerobic exercise (but no lower than 10-min in duration) is recommended as one approach
for achieving targeted volumes.
3.4. Mode of Exercise
Modes of exercise that produce substantive acute increases in oxygen
consumption are continuous, rhythmic and use a large amount of muscle mass, such as
walking, running, cycling and swimming. Consequently, a variety of exercise modes can
successfully be used to improve cardiorespiratory fitness.(Pollock et al., 1998) While
central adaptations of the cardiopulmonary system can be obtained with a variety of
modes, local muscular adaptations are specific to the muscle(s) being trained.(Pollock et
al., 1998)
Within limits, the more muscle mass that can be engaged during a given exercise,
the higher will be the VO2. Swimming utilizes less muscle mass than cycling, thus
triathletes - who are well trained in both modes - have a higher VO2max while
cycling.(Roels et al., 2005) However, when individuals are highly trained in only one
mode of exercise, VO2max in that mode may equal or exceed that in modes using a greater
muscle mass. Swimmers who train in swimming but not cycling have a higher VO2max
when swimming.(Roels et al., 2005) Running utilizes more muscle mass than cycling,
and runners have an 11% higher VO2max running than swimming.(Bassett and Boulay,
2000) However, for triathletes, the difference is only 6%, and for cyclists the difference is
less than 3%, demonstrating an interaction of muscle mass and training
specificity.(Bassett and Boulay, 2000)
Some modes of exercise, such as running, have greater impact forces and thus
entail greater orthopedic stress than other modes, such as cycling and swimming.
Therefore, greater caution must be used when increasing volume or intensity in higher
impact modes of exercise. However, high impact also provides greater stress for the
development of bone mineral density.(NEED REFS) Therefore, individual consideration
must be made to optimize bone health while minimizing the risk of orthopedic and
overuse injury.
Resistance training is valuable for improving muscular strength (see below). It
can cause a modest increase in VO2max in sedentary individuals, but should not be
considered a primary means of improving cardiorespiratory fitness.(Pollock et al., 1998)
Even circuit resistance training, involving moving from one exercise station to others in
rapid sequence, produces little improvement in VO2max.(Pollock et al., 1998) Compared
to aerobic modes of exercise, acute resistance training elicits a higher heart rate at a given
VO2,(Baum et al., 2005) or a lower VO2 at a given heart rate.(Bloomer, 2005) An
elevated heart rate does not indicate an aerobic training stimulus unless the mode of
exercise is aerobic.
3.5. Individual Variability
While the basic principles of training apply to all individuals, the degree of
adaptation, such as an increase in VO2max, varies with several factors, including baseline
fitness, sex, age and genetics.
3.5.1. Baseline Fitness
As noted above, increases in VO2max following training are inversely related to
baseline fitness, that is, for a given training stimulus, individuals with low baseline fitness
will demonstrate greater percentage increases in VO2max. Alternatively, less intensity of
training is needed to produce comparable changes in fitness. Consistent with the
progression principle of training, as fitness improves, the intensity of training must
increases if further increases in VO2max are desired.
3.5.2. Sex
There are clear physiological differences between men and women that impact the
development of VO2max. Women have a lower oxygen-carrying capacity and have lower
potential for reaching the highest levels of VO2max.(Pollock et al., 1998) However,
women have equal adaptive responses to men following standard training
regimens.(Pollock et al., 1998)
3.5.3. Age
Aerobic capacity declines with age, however, the rate of decline is strongly
influenced by physical activity.(Pollock et al., 1998) Sedentary elderly respond similarly
to younger adults to aerobic training.(Pollock et al., 1998)
3.5.4. Genetics
3.6. Maintenance (Franklin)
3.7. Detraining (Franklin)
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TABLE 1. Cardiorespiratory Exercise Intensity: Comparison of Methods
%HRR or
VO2R
%HRmax*
RPE*
20 MET
10 MET
5 MET
%VO2max
%VO2max
%VO2max
Light
30
57
10
34
37
44
Moderate
40
64
12
43
46
52
50
70
13
53
55
60
60
77
14
62
64
68
70
84
16
72
73
76
80
91
17
81
82
84
Near-
90
96
19
91
91
92
maximal
100
100
20
100
100
100
Vigorous
* Values for %HRmax are approximate, and vary with resting HR. Values for RPE are
crude, and should be confirmed during supervised exercise.
HRR = heart rate reserve; VO2R = oxygen consumption reserve; HRmax = maximum heart
rate; RPE = rating of perceived exertion, 6-20 scale;(Borg, 1974) MET = metabolic
equivalents (multiples of 3.5 mL.min-1.kg-1); VO2max = maximum oxygen consumption.
Adapted from Howley, 2001, and GETP8 Table 1.2.
Table 2. Recent clinical trials that controlled volume in two or more intensity groups
Study
Subjects
Intensity
groups
(%VO2R)
72
48
Initial VO2max
(mL.min-1.kg-1)
Kang et al.,
2002
13-16 y,
M/F
Asikainen
et al., 2003
57 y, F
60
49
38
29
30
31
8.7
9.6
8.4
Rognmo et
al., 2004
O’Donovan
et al., 2005
Warburton
et al., 2005
62 y, M/F
(CHD)
41 y, M
83 int
49
75
55
90 int + 65
65
31.8
32.1
31.8
31.0
32
18*
8
22*
16
18
13
DiPietro et
al., 2006
73 y, F
76
58
21.4
21.2
ns
ns
Helgerud et
al., 2007
25 y, M
Wisloff et
al., 2007
76 y, M/F
(HF)
85 int
72
47
90 int
47
55.5
59.6
55.8
13
8.8
ns
ns
46*
14
Esfarjani &
Laursen,
2007
Nemeto et
al., 2007
19 y, M
100 int + 75
75
51.3
51.8
9.1
ns
63 y, M/F
64 int
41
22.3
22.4
9
ns
Gormley et
al.,
submitted
21 y, M/F
95 int
75
50
35.7
33.6
35.3
20.6*
14.3*
10.0
56 y, M
(CHD)
19.6 overall
VO2max
Increase
(%)
23.9*
11.6
Other changes
Only 72% group
had decrease in
dia BP and
triglycerides,
and increase in
LDL particle
size
Only 60% group
had decrease in
dia BP and
fasting glucose
Only 75% group
decreased LDL
Only 90% group
increased VT
and time to
exhaustion
Only 76% group
increased insulin
sensitivity
Only 90%
increased LV
function
Only 100%
group increased
LT
Only 64% group
decreased dia
BP, increased
thigh strength;
64% group had
greater decrease
in sys BP
%VO2R = percentage of oxygen consumption reserve; VO2max = maximum oxygen
consumption; M = male; F = female; BP = blood pressure; dia = diastolic; sys = systolic;
LDL = low density lipoprotein-cholesterol; CHD = coronary heart disease patients; HF =
heart failure patients; int = interval training; ns = not significant; * = significantly greater
than next group.