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ORIGINAL ARTICLE
Cardiocirculatory and metabolic responses at different
walking intensities
M Schwarz, A Urhausen, L Schwarz, T Meyer, W Kindermann
...............................................................................................................................
See end of article for
authors’ affiliations
.......................
Correspondence to:
Dr Schwarz, Institute of
Sports and Preventive
Medicine, University of
Saarland, Saarbru¨cken,
Germany; mschwarz@mx.
uni-saarland.de
Accepted 6 June 2005
.......................
Br J Sports Med 2006;40:64–67. doi: 10.1136/bjsm.2005.020198
Objectives: Although walking is a common physical activity, scientifically based training guidelines using
standardised tests have not been established. Therefore this explorative study investigated the
cardiovascular and metabolic load resulting from different walking intensities derived from maximal
velocity (V
max
) during an incremental treadmill walking test.
Methods: Oxygen uptake, heart rate (HR), blood concentrations of lactate and catecholamines, and rating
of perceived exertion were recorded in 16 recreational athletes (mean (SD) age 53 (9) years) during three
30 minute walking trials at 70%, 80%, and 90% of V
max
(V
70
,V
80
, and V
90
) attained during an
incremental treadmill walking test.
Results: Mean (SD) oxygen uptake was 18.2 (2.3), 22.3 (3.1), and 29.3 (5.0) ml/min/kgatV
70
,V
80
, and
V
90
respectively (p,0.001). V
70
led to a mean HR of 110 (9) beats/min (66% HR
max
), V
80
to 124 (9)
beats/min (75% HR
max
), and V
90
to 152 (13) beats/min (93% HR
max
)(p,0.001). Mean (SD) lactate
concentrations were 1.1 (0.2), 1.8 (0.6), and 3.9 (2.0) mmol/l at V
70
,V
80
, and V
90
respectively
(p,0.001). There were no significant differences between catecholamine concentrations at the different
intensities. Rating of perceived exertion was 10 (2) at V
70
, 12 (2) at V
80
, and 15 (2) at V
90
. Twelve subjects
reported muscular complaints during exercise at V
90
but not at V
70
and V
80
.
Conclusions: Intensity and heart rate prescriptions for walking training can be derived from an incremental
treadmill walking test. The cardiovascular and metabolic reactions observed suggest that V
80
is the most
efficient workload for training in recreational athletes. Further studies are needed to confirm these findings.
O
ver the last few decades, walking has been established
as one form of endurance training for preventive
purposes. Sufficient training effects with little risk of
overstrain have been suggested.
1–4
Data on appropriate
training intensities for walking vary in the literature, and
published test procedures only partly allow training recom-
mendations to be derived. With regard to intensity, many
authors refer to maximal heart rate or maximal oxygen
uptake.
5–7
For efficient cardiocirculatory training, the
American College of Sports Medicine (ACSM) recommends
55/65–90% of maximal heart rate (HR
max
) or 40/50–85% of
maximal oxygen uptake reserve (V˙
O
2R
)orHR
max
reserve
(HR
R
).
8
However, approaches that use an incremental tread-
mill walking test (ITWT) as the basis for individual training
recommendations are rare.
9–11
The purpose of this study was to check whether an ITWT is
applicable for the derivation of individual training recom-
mendations. A secondary aim was to investigate if walking
allows middle aged people to reach sufficient training
intensity at comfortable speeds.
METHODS
This study was approved by the institution’s review board
and complies with the Declaration of Helsinki. Each
participant gave written informed consent.
Subjects
Sixteen healthy subjects (10 men, six women) took part in
the study. Their mean (SD) age was 53 (9) years, height 169
(8) cm, and weight 67 (11) kg. They were familiar with the
walking technique and had been participating in recreational
sport for an average of 34 months. Mean (SD) P
max
obtained
from an incremental cycling test was 2.6 (0.6) W/kg.
Study design
Firstly, all subjects had a clinical and laboratory routine
examination and performed an incremental cycling test to
rule out any health risks. Two to seven days later an ITWT
was conducted followed by three walking tests at constant
velocities: 70%, 80%, and 90% of the maximal velocity (V
max
)
obtained during the ITWT. Figure 1 shows the course of the
study. The test period ranged between two and four weeks for
each subject. The participants were told to neither change
their normal training load during the study nor perform
intensive or prolonged physical exercise on the day before the
tests.
ITWT
One ITWT was performed for training purposes two to seven
days before the second ITWT which served as the basis for the
later tests of constant velocity. Starting at 4.3 km/h, the
velocity was increased by 0.7 km/h every three minutes until
exhaustion or V
max
was reached with the appropriate walking
technique (no race walking or running). The test was carried
out without treadmill inclination to simulate as close as
possible walking in the field. After two to seven days, a
second identical ITWT was performed. During these tests, HR
was measured and recorded continuously with a portable
device (Accurex-Plus; Polar, Kempele, Finland). For the
determination of the blood lactate concentration (Super GL;
Greiner, Flacht, Germany), capillary blood was taken from
the hyperaemised earlobe at rest and after each stage during
a break of about 20 seconds. From the lactate curve, the
individual anaerobic threshold (IAT) was determined by the
Abbreviations: HR, heart rate; IAT, individual anaerobic threshold;
ITWT, incremental treadmill walking test; RPE, rating of perceived
exertion; V˙
O
2
, oxygen uptake
64
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method of Hagberg and Coyle,
12
which was evaluated with
race walkers. For the radioenzymatic determination of
catecholamines
13
before and immediately after exercise,
300 ml arterialised capillary blood was taken from the
hyperaemized earlobe. In addition, gas exchange parameters
(Meta-Max; Cortex, Leipzig, Germany) were continuously
measured, and the rating of perceived exertion (RPE)
recorded.
14
With reference to V
max
, individual intensities for three
constant velocity exercises were determined (70%, 80%, and
90% of V
max
=V
70
,V
80
, and V
90
).
Walking endurance exercises
The subjects walked at the three intensities (V
70
,V
80
, and
V
90
) on the same treadmill for 30 minutes in random order.
Before the 30 minute exercise, each subject walked for three
minutes at V
70
to warm up. During the exercise and for three
minutes after it had finished, HR and oxygen uptake (V˙
O
2
)
were continuously measured. With reference to V˙
O
2
and
respiratory exchange ratio, energy output was calculated;
3.5 ml/min/kg was considered to be 1 MET. Capillary samples
for determination of lactate and catecholamine as well as the
recording of RPE were carried out after 10 and 20 minutes of
exercise during a 30 second break. Technical abnormalities
and physical complaints were only recorded; no quantifica-
tion was performed.
Statistical analysis
After normal distribution of data had been confirmed with
the Kolmogoroff-Smirnov test, descriptive statistical analysis
was performed; mean (SD) values were calculated. In the
case of normally distributed data, a two factorial (intensity
and time) analysis of variance was performed. The Scheffe´
test was used for post hoc comparisons. For ordinally scaled
values (RPE), calculations were performed by non-para-
metric procedures (rank correlation according to Spearman).
The significance level for the a error was set at p,0.05.
RESULTS
ITWT
During the ITWT, the subjects reached a mean (SD) V
max
of
8.3 (0.6) km/h, and a mean (SD) V˙
O
2
MAX of 33.2 (5.1) ml/
min/kg. Table 1 gives the ITWT results.
Walking trials
Oxygen uptake
The subjects reached a V˙O
2
of 18.2 (2.3) ml/min/kg (55%
V˙
O
2
MAX)atV
70
, 22.3 (3.1) ml/min/kg at V
80
(67% V˙O
2
MAX),
and 29.3 (5.0) ml/min/kg at V
90
(88% V˙O
2
MAX). There was a
significant effect of intensity on V˙
O
2
. Figure 2 gives the
results from post hoc testing. At V
80
,V
90-
, and V
IAT
all
subjects were above 60% V˙
O
2
MAX.
HR
Mean HR reached 110 (9) beats/min during V
70
(66% HR
max
),
124 (9) beats/min during V
80
(75% HR
max
), and 152 (13)
beats/min during V
90
(93% HR
max
) (fig 3). During V
80
and
V
90
all subjects were above 65% HR
max
. HR during the 80%
endurance exercise was significantly (p,0.05) lower than HR
at IAT (131 (14) beats/min, 79% HR
max
). There was a
significant effect of intensity on HR. Figure 3 shows different
results from post hoc testing.
Lactate concentration
During the 30 minute walking tests, mean lactate concentra-
tion reached 1.1 (0.2), 1.8 (0.6), and 3.9 (2.0) mmol/l at V
70
,
V
80
, and V
90
respectively. There was a significant effect of
intensity on lactate between V
70
and V
80
as well as between
V
80
and V
90
(fig 4).
Energy consumption
The total energy consumption during the 30 minute walking
tests was 744 (93) kJ (177 (22) kcal or 5.2 (0.7) MET) at V
70
,
930 (129) kJ (221 (31) kcal or 6.3 (2.5) MET) at V
80
, and
1224 (207) kJ (291 (49) kcal or 8.4 (1.4) MET) at V
90
. There
was a significant effect of intensity (p,0.001).
Catecholamine concentration
The catecholamine concentrations did not differ significantly
between the three intensity levels. After 30 minutes of
Physical examination and laboratory screening
Incremental cycling test (P
max
)
Maximal velocity (V
max
)
80% (V
80
) 90% (V
90
) of V
max
70% (V
70
)
Incremental treadmill walking test
2–7 days
30 minute walking tests
Randomised order
2–7 days
Figure 1 Overview of the study design.
Table 1 Results from the incremental treadmill walking
test
Variable Max IAT
Velocity (km/h) 8.3 (0.6) 6.9 (0.6) (83% V
max
)
Heart rate (beats/min) 166 (14) 131 (14)
Lactate (mmol/l) 6.1 (1.8) 2.0 (0.3)
V˙
O
2
MAX (ml/min/kg) 33.2 (5.1) 23.4 (4.8)
Energy cost (kJ/min) 46.7 (7.1) 32.9 (6.8)
MET 9.5 (1.5) 6.7 (1.4)
Values are maximal performance (Max) and individual anaerobic
threshold (IAT) during walking and are expressed as mean (SD) (n = 16).
40
34
28
22
16
10
4
Time (minutes)
V
70
(5.8 km/h)
VO
2
(ml/min/kg)
·
Rest 10 20 30
V
80
(6.6 km/h)
V
90
(7.5 km/h)
Figure 2 Oxygen uptake (V˙ O
2
) during the 30 minute walking trials at
70%, 80%, and 90% of the maximal velocity obtained in the incremental
treadmill walking test (V
70
,V
80
, and V
90
). Values are mean (SD) (n =
16). All three values at each time point are significantly different from
each other (p,0.001).
Cardiocirculatory and metabolic responses at different walking intensities 65
www.bjsportmed.com
walking, the mean maximal free noradrenaline concentra-
tions were 6.48 (2.17), 5.47 (1.34), and 6.26 (1.76) nmol/l at
V
70
,V
80
, and V
90
respectively. The corresponding adrenaline
concentrations were 1.17 (0.28), 1.00 (0.27), and 1.10
(0.31) nmol/l.
RPE
A mean RPE of 10 (2) (‘‘very easy’’ to ‘‘quite easy’’), 12 (2)
(‘‘quite easy’’ to ‘‘a little difficult’’), and 15 (2) (‘‘difficult’’)
was recorded at V
70
,V
80
, and V
90
respectively. There was a
significant effect of intensity on RPE (p,0.001). An RPE of
19 (‘‘very, very difficult’’) was reported by one subject during
V
90
. At the end of the endurance test, 12 subjects felt that
walking at V
80
was more comfortable than at V
70
or V
90
.
Complaints
At V
90
, 12 out of 16 subjects reported physical problems
mainly in the lower legs. During V
70
and V
80
, no problems
were reported by the subjects.
DISCUSSION
It has been shown that V˙O
2
during V
70
corresponds to the
minimum intensity (55% V˙
O
2
MAX) for training as recom-
mended by ACSM, whereas V
90
approaches the upper limit
(88% V˙
O
2
MAX).
8
Thus, low intensity walking at V
70
may lead
to health benefits when it is performed frequently and for
long enough.
15
However, V
80
(67% of V˙O
2
MAX) may be more
appropriate for efficient endurance training. All subjects were
above 60% V˙
O
2
MAX or 50% V˙O
2R
during V
80
. In contrast, V
90
seems quite often to induce muscle pain in the lower legs
even after only 30 minutes.
The mean maximal HR reached 220 minus age, indicating
sufficient maximal effort on a treadmill.
16
If the mean HR
response of the three walking endurance exercises is
considered, at V
70
the subjects are at the minimum HR,
and at V
80
and V
90
they are within the recommended HR
range. At V
80
and V
90
, all subjects are above the minimum HR
described by ACSM.
8
The mean lactate concentration during V
70
was similar to
resting concentrations, suggesting that the exercise intensity
is low. During V
90
the mean lactate concentration indicates
intense physical performance. The mean lactate concentra-
tion during V
80
was close to the IAT and within the range of
extensive endurance training and
17
and thus compatible with
appropriate recreational intensity.
According to Morris and Hardman,
3
in people with a body
weight of about 70 kg, the energy consumption during
walking on even ground at a velocity of 6.4–8.0 km/h
corresponds to 25–36 kJ/min. In 40–56 year old men,
Pollock et al
7
measured an energy consumption of 28.3–
36.5 kJ/min for a velocity range of 6.8–7.6 km/h. The results
of our study (5.8–7.5 km/h and 25–40 kJ/min) correspond
well to these results.
The catecholamine concentrations did not differ signifi-
cantly between intensities. Therefore this variable may not be
suitable for defining efficient walking intensities. If the
observed concentrations of noradrenaline and adrenaline are
compared with those from earlier studies for cardiac patients
during a strength endurance circuit and badminton training,
they fall in the same range.
18 19
Another variable that suggests that V
80
is an adequate
exercise intensity is the mean RPE (12 (2)). Dishman
20
recommends the same RPE for endurance training with
appropriate intensity. Spelman et al
21
recommended an RPE
of ‘‘quite easy’’ (Borg scale 11) for walking training with 50%
190
170
150
130
110
90
70
Time (minutes)
V
70
(5.8 km/h)
Heart rate (beats/min)
Rest 10 20 30
V
80
(6.6 km/h)
V
90
(7.5 km/h)
Figure 3 Heart rate during the 30 minute walking trials at 70%, 80%,
and 90% of the maximal velocity obtained in the incremental treadmill
walking test (V
70
,V
80
, and V
90
). Values are mean (SD) (n = 16). All
three values at each time point are significantly different from each other
(p,0.001).
6
5
4
3
2
1
4
Time (minutes)
†††
†††
††
V
70
(5.8 km/h)
Lactate concentration (mmol/l)
Rest 10 20 30
V
80
(6.6 km/h)
V
90
(7.5 km/h)
Figure 4 Lactate concentration during the 30 minute walking trials at
70%, 80%, and 90% of the maximal velocity obtained in the incremental
treadmill walking test (V
70
,V
80
, and V
90
). Values are mean (SD) (n =
16). ***Significantly different from V
80
and V
70
(p,0.001), ,
significantly different from V
70
(p,0.01, p,0.001 respectively).
What is already known on this topic
N
Data on appropriate training intensities for walking
vary in the literature, and published test procedures
only partly allow training recommendations to be
derived
N
Approaches using an incremental treadmill walking
test (ITWT) as the basis for individual training
recommendations are rare
What this study adds
N
An ITWT is applicable for deriving individual intensity
recommendations for walking training
N
The most promising intensity is 80% of the maximal
velocity reached during ITWT
66 Schwarz,Urhausen,Schwarz,etal
www.bjsportmed.com
of V˙O
2
MAX. Also, the 70% walking endurance performance
was subjectively perceived as too low (‘‘very easy’’) and V
90
was too intense and described as ‘‘very difficult’’.
Furthermore, orthopaedic problems occurred during the
highest exercise intensity, mainly with pretibial muscles, as
in earlier studies with recreational athletes.
22 23
Although
symptoms in most cases disappeared quickly after exercise,
straining beyond the pain limit should be avoided, as
irreversible damage such as neurological disorders and
muscle necroses has been described.
24 25
In conclusion, an ITWT is appropriate for deriving
individual intensity recommendations for walking training.
The most promising intensity is 80% of the maximal velocity
reached during ITWT.
Authors’ affiliations
.....................
M Schwarz, L Schwarz, T Meyer, W Kindermann, Institute of Sports and
Preventive Medicine, University of Saarland, Saarbru¨cken, Germany
A Urhausen, Centre de l’ Appareil Locomoteur, de Medicine du Sport et
de Pre´vention, Luxembourg
Competing interests: none declared
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