Available online at www.sciencedirect.com
Journal of Science and Medicine in Sport 15 (2012) 259–265
Original research
Is the six-minute walk test appropriate for detecting changes in
cardiorespiratory fitness in healthy elderly men?
Marcos G. Santana a,b,c,∗ , Claudio A.B. de Lira c , Giselle S. Passos a,c ,
Carlos A.F. Santos d , Alan H.O. Silva a , Cristina H. Yoshida a , Sergio Tufik a , Marco T. de
Mello a,b
a
Disciplina de Medicina e Biologia do Sono, Departamento de Psicobiologia - Universidade Federal de São Paulo, Brazil
b Programa de Pós-graduação em Nutrição - Universidade Federal de São Paulo, Brazil
c Universidade Federal de Goiás - Campus Jataí, Brazil
d Disciplina de Geriatria e Gerontologia, Departamento de Medicina - Universidade Federal de São Paulo, Brazil
Received 11 August 2011; received in revised form 4 November 2011; accepted 10 November 2011
Abstract
Objectives: The purpose of this study was to determine whether the six-minute walk test (6-MWT) can detect changes in cardiorespiratory
fitness (CRF) induced by exercise training in healthy elderly men.
Design: Randomized and prospective controlled trial.
Methods: Thirty-two healthy untrained men, between 65 and 75 years of age, were randomly assigned to one of three groups: control (C,
n = 12), endurance training (E, n = 10), or concurrent training (ER, n = 10). Training groups underwent 24 weeks of exercise, 3 times a week.
All participants were subjected to cardiopulmonary exercise testing and the 6-MWT, before and after the training period.
Results: At follow-up, the E and ER groups had significantly higher peak oxygen uptake (V̇ O2 peak) (15.0 ± 9.1 and 12.6 ± 10.4%, respectively) and 6-MWT distances (5.5 ± 5.3 and 4.6 ± 2.8%, respectively) compared to the C group. In pre-intervention (n = 32), the 6-MWT
distance correlated positively with (V̇ O2 peak) (r = 0.51, p = 0.001) and V̇ O2 at anaerobic threshold (r = 0.39, p = 0.010). On the other hand,
there was no significant correlation between the changes (after–before) in the 6-MWT distance and V̇ O2 peak (E and ER groups: r = 0.38,
p = 0.097).
Conclusions: The 6-MWT is not appropriate to evaluate changes in CRF in healthy elderly men who performed endurance and concurrent
training for 24 weeks.
© 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
Keywords: Concurrent training; Physical activity; Older adults; Incremental exercise test; Functional capacity
1. Introduction
Chronic exercise has been recommended as an important tool to reduce the risk of cardiovascular and endocrine
diseases and to improve bone and muscle conditioning in
elderly people.1 It is well established that chronic aerobic
exercise improves maximal oxygen uptake due to central
and peripheral cardiac adaptations.2 Additionally, exercise
∗
Corresponding author.
E-mail addresses: [email protected] (M.G. Santana),
[email protected] (M.T. de Mello).
interventions that improve endurance and neuromuscular
performance in elderly people are becoming recognized as
effective strategies to increase functional independence and
to decrease the prevalence of many diseases associated with
aging.1 In concurrent training, both endurance and strength
performance can be simultaneously improved in untrained
participants.3
Traditionally, improvements in aerobic power are assessed
by increases in peak/max oxygen uptake (V̇ O2 peak/max).
This physiological variable is considered the gold standard
in the assessment of functional capacity and cardiorespiratory fitness (CRF) and is measured by cardiopulmonary
1440-2440/$ – see front matter © 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.jsams.2011.11.249
260
M.G. Santana et al. / Journal of Science and Medicine in Sport 15 (2012) 259–265
exercise testing (CPET).4 CPET analyses the function of the
cardiovascular, respiratory and neuromuscular systems, providing a global assessment of the integrative physiological
response.5 Clinically, a low CRF is associated with allcause mortality and cardiovascular diseases (CVD) events
in healthy individuals.6 In addition, physical performance
have great value when used as baseline factors to discriminate future health and function in elderly people.7 However,
CPET is a high-cost exam and requires specially trained staff.
Therefore, simple and inexpensive tests are required in the
field to assess functional capacity.8
The 6-min walk test (6-MWT) is a simple, safe and lowcost field test often used for the elderly and patients with
chronic heart failure or chronic obstructive pulmonary disease to regularly assess their functional exercise capacity
and the effects of a rehabilitation/exercise program.4 Previous studies have used the 6-MWT performance to predict
the V̇ O2 peak in clinical populations,9 as well as in healthy
elderly people.10 Kervio et al.10 estimated the V̇ O2 peak
in healthy elderly from anthropometric values and 6-MWT
parameters. More recently, Ross et al.9 demonstrated that
the 6-MWT is appropriate to estimate V̇ O2 peak in patients
with moderate-to-severe heart or lung disease, using only the
covered distance.
Some studies have investigated the association between
the distance covered obtained from CPET and the 6MWT performance.11,12 In this way, correlations have been
observed between the distance covered during the 6-MWT
and V̇ O2 peak in elderly healthy participants.11,12 However,
to our knowledge, there are no studies that used the 6-MWT
performance to evaluate improvement in cardiorespiratory
parameters in healthy elderly men submitted to chronic exercise. We hypothesised that changes in CRF could be detected
by changes in the 6-MWT performance. Thus, the aim of
this study was to analyse whether the 6-MWT can detect
changes in CRF induced by exercise training (endurance and
concurrent) in elderly men.
2. Methods
The thirty-two participants, recruited using advertisements placed in local newspapers, were healthy men between
65 and 75 years old. The inclusion factors used for the healthy
elderly were: untrained, no current smoking, no chronic disease, and a body mass index lower than 35 kg m−2 . After
a clear explanation of the procedures, including the risks
and benefits of participation, written informed consent was
obtained. Participants underwent a detailed medical examination and an electrocardiogram test. Participants then were
randomly assigned to one of three groups: control group (C,
n = 12, age: 69.8 ± 1.6 years, height: 168.7 ± 8.4 cm, body
mass: 75.9 ± 8.9 kg, body mass index: 26.6 ± 2.0 kg m−2 ),
endurance training group (E, n = 10, age: 70.0 ± 2.8 years,
height: 168.4 ± 6.2 cm, body mass: 75.0 ± 7.0 kg, body mass
index: 26.5 ± 2.6 kg m−2 ), or concurrent training group (ER,
n = 10, age: 67.6 ± 3.1 years, height: 171.7 ± 3.2 cm, body
mass: 71.9 ± 9.7 kg, body mass index: 24.3 ± 3.1 kg m−2 ).
All experimental procedures were approved by the Ethics
Committee of Federal University of Sao Paulo (Sao
Paulo – Brazil) in accordance with the Declaration of
Helsinki.
The study was organised in four successive phases: basal
medical examination, pre-intervention evaluations, training period and post-intervention evaluations. Basal medical
examination was performed three weeks before the beginning of the training period. Participants underwent a detailed
medical examination and an electrocardiogram test, with
direct medical supervision, to volitional fatigue on a treadmill (Micromed, Centurion 200, São Paulo, Brazil). In the
week before and after the training period, all the participants
performed three exercise tests in the following order: CPET,
6-MWT and 1-RM test. These tests were separated by at least
48 h of rest.
Participants were instructed to arrive at the laboratory in a
rested and fully hydrated state, having not consumed caffeine
in the previous 4 h, and to avoid strenuous exercise in the 48 h
preceding a test session. To minimise the effects of diurnal
biological variation, all the tests were performed in the same
time of day (10:00 a.m. ± 2 h).
Participants were given a standardised set of instructions
explaining the CPET test. After these preliminary procedures,
the participants were submitted to an exercise test on a treadmill (Life Fitness, 9500 HR, Chicago, IL, USA). Following a
previous study, the test started at 1.6 km h−1 , followed by progressive increases in the treadmill speed and slope at a rate of
0.8 km h−1 and 1%, respectively, every 2 min until volitional
exhaustion was reached.13 Respiratory gas samples were
analysed breath-to-breath using a portable metabolic system
(K4b2 , Cosmed SRL, Pavona, Rome, Italy). Before each test,
the gas analysers were calibrated according to the manufacturer’s recommendations. Heart rate (HR) was recorded
using a HR monitor (Polar Electronics, FS1, Kempele, Oulu,
Finland).
Peak oxygen uptake and HRmax were defined as the
mean oxygen uptake (V̇ O2 ) and HR values, respectively, during the last 20 s of exercise. The anaerobic threshold (AT)
was estimated by the gas exchange method,14 inspecting the
inflection point of carbon dioxide output (V̇ CO2 ) with respect
to V̇ O2 and, secondarily, by the ventilatory method15 when
ventilatory equivalent for O2 (V̇ E/V̇ O2 ) and end-tidal partial
pressures for O2 (PETO2 ) increased, while ventilatory equivalent for CO2 (V̇ E/V̇ CO2 ) and end-tidal partial pressures for
CO2 (PETCO2 ) remained stable.
The 6-MWT was performed twice to minimise the learning effect. The tests were separated by at least 1 h of
recovery. These technical aspects are in line with the American Thoracic Society recommendations for the 6-MWT.8 The
6-MWT was performed in a 20-m-long indoor hallway free
of obstacles. The length of the corridor was marked every
1 m. Participants were instructed to walk at a self-selected
regular pace to cover as much distance as they could during
M.G. Santana et al. / Journal of Science and Medicine in Sport 15 (2012) 259–265
the allotted time. If necessary, slowing down and stopping to
rest were allowed. At the end of each minute participant were
given feedback on the elapsed time and standardised encouragement in the form of statements such as “you are doing
well, keep it up” and “do your best.”16 The highest distance
between two tests was used for the statistical analysis.
To better characterise physiological response during the 6MWT, V̇ O2 and HR were defined as the mean obtained during
the last 20 s of exercise. These parameters were measured
with the same metabolic system used in the CPET, previously
described and validated.17
Strength performance was assessed by one repetition maximum (1-RM) test18 to determine maximal strength in the
following strength devices: (1) chest press, (2) leg press, (3)
vertical traction, (4) leg curl, (5) bicep curl, (6) abdominal
crunch, (7) arm extension, and (8) lower back (Technogym,
Gambettola, Italy). Briefly, the 1-RM test protocol consisted
of a 5-min warm-up on a cycloergometer (Life Fitness, 9500
HR, Chicago, IL, USA) followed by static stretching exercises, then two series with eight repetitions on the test devices,
the first with a light load and the second with a heavy one, then
the first attempt at the test increasing load until the maximum
was obtained in one repetition. There were at most three subsequent attempts at 3-min intervals. The examiner constantly
encouraged the participants. All participants were tested by
a single evaluator who was trained and experienced in 1-RM
test. The participants had three sessions to become familiar
with the equipment. The strength tests were performed before
(week 0), during (weeks 6, 12, and 18), and after (week 24)
the training period. The tests in week 0 served to determine
individual workloads. The tests in weeks 6, 12, and 18 served
for workload adjustment.
Participants in each group participated in their respective
training program for 24 weeks (72 training sessions). The
exercise protocols were designed in accordance with published guidelines for elderly people.19,20 All training sessions
were supervised by experienced exercise instructors. All participants of training groups completed 72 exercise sessions.
Missed training sessions were compensated for during the
subsequent training weeks so that the total amount of training
sessions was reached.
The endurance training protocol consisted of supervised
walking/jogging on a treadmill (Life Fitness, 9500 HR,
Chicago, IL, USA) three times per week on non-consecutive
days. The grade of the treadmill was set at 0%. Training
intensity and duration were progressively increased within
the 24 weeks. Exercise duration was limited to 30 min during
the first and second weeks and was then increased by 5 min
biweekly until week 8; after that, exercise duration was fixed
at 45 min. Training intensity was determined by the percentage of heart rate reserve (HRR).21 Resting measures of HR
were recorded after each participant had sat quietly in a chair
for 5 min. The average values of HR recorded over the last
minute were considered to be the resting values, as has been
previously reported.22 Training intensity was set at 50% of
HRR until the 8th week, then intensity was progressively
261
increased (55% in weeks 9 and 10, 60% in weeks 11 and 12,
65% in weeks 13 through 16, 70% in weeks 17 through 20,
and 75% for the rest of the training period). Participants could
exercise within ±5 bpm of the prescribed intensity. Each session included a warm-up and cool-down period involving
5 min of low-intensity walking.
The concurrent training protocol consisted of endurance
and resistance training. Endurance training had the same
characteristics as the E group. Resistance training was performed in this order: (1) chest press, (2) leg press, (3) vertical
traction, (4) leg curl, (5) bicep curl, (6) abdominal crunch, (7)
arm extension, and (8) lower back (Technogym, Italy). The
individual loads were determined on the bases of the initial 1RM test. Resistance training used 50% of the 1-RM in weeks
1–4, 55% in weeks 5–8, 60% in weeks 9–12, 70% in weeks
13–16, 75% in weeks 17–20, and 80% in weeks 21–24. The
participants were instructed to perform three sets of 12 repetitions of each activity in weeks 1–12 and three sets of 10
repetitions in weeks 13–24. Each set was interspersed by a
90-s recovery interval. Each session included a warm-up and
cool-down period involving 5 min of low-intensity cycling
and had a duration of approximately 60 min. The concurrent training protocol included three sessions per week on
non-consecutive days. In each session, the mode of exercise
alternated between endurance and resistance training; therefore, participants completed 50% of each of the endurance
and resistance training sessions.
The C group underwent testing as described above and
were asked not to make changes in their physical activity
habits over the 24-week treatment period. They received
monthly follow-up phone calls during the treatment period.
STATISTICA version 7.0 for Windows was used for statistical analyses. All variables presented normal distributions
(p > 0.05) according to Kolmogorov–Smirnov tests. Prior to
intervention, significant differences were analysed by oneway analysis of variance (ANOVA). The changes in study
variables between the groups were compared with an analysis of co-variance (ANCOVA) using the pre-intervention
values (week 0) as the covariates. ANCOVA was chosen
to eliminate any effect of the relation between the variables
and their pre-intervention values. When a significant effect
was achieved, Tukey’s post hoc procedures were performed
to identify differences between the means. Within group
analyses were performed with paired samples t-tests. Pearson product-movement correlation coefficient was used to
assess relationships between the CPET and 6-MWT parameters. Differences were considered significant at the level of
p < 0.05. Data are presented as the means ± SD.
3. Results
The treadmill performances of the participants are shown
in Table 1. No significant differences were observed between
groups before the training period. The V̇ O2 peak obtained
after the training period was significantly higher in the E
262
10.4b
6.9
6.9
7.4b
±
±
±
±
12.7
3.6
3.6
11.4
5.8 a
13.5
8.4
1.6 a
±
±
±
±
33.2
161.8
106.6
17.3
3.7
14.0
8.1
1.9
Data are presented as the mean ± SD. C: control group; E: endurance training group; ER: concurrent training group; V̇ O2 : oxygen uptake; HR: heart rate.
a p < 0.05, post different from pre.
b p < 0.05, significant difference versus the control group.
±
±
±
±
9.1b
7.6 b
7.6 b
12.2 b
±
±
±
±
5.5 a
11.0
7.4
2.5 a
3.7
14.5
9.4
1.4
3.3
18.2
12.3
1.4
±
±
±
±
28.2
149.2
99.3
15.3
28.0
150.7
100.3
15.0
±
±
±
±
−0.9
1.6
1.6
−1.5
±
±
±
±
8.5
7.3
7.3
4.9
27.3
147.2
98.2
15.2
±
±
±
±
3.7
13.6
9.1
1.5
31.5
158.0
105.4
17.9
±
±
±
±
15.1
7.8
7.8
18.7
28.9
156.6
103.1
15.6
10.7
−3.2
−1.2
-3.3
17.8
53.9
103.5
64.2
2.2
6.7
9.2
6.2
±
±
±
±
16.2
56.4
105.3
67.5
18.0
10.8
8.1
6.5
±
±
±
±
1.3
−12.3
0.6
−4.6
3.1
3.4 a
10.2
4.5
±
±
±
±
−9.8
−8.9
−1.0
−1.8
1.9a
7.6a
8.4
4.8
±
±
±
±
13.4
48.6
93.1
62.0
2.1
7.2
15.0
6.0
±
±
±
±
15.0
53.5
95.2
63.8
At anaerobic threshold
V̇ O2 (mL kg−1 min−1 )
% V̇ O2 peak
HR (bpm)
% Attained HRmax
At maximal exercise
V̇ O2 (mL kg−1 min−1 )
HR (bpm)
% Predicted HRmax
Duration (min)
Pre
Post
%
±
±
±
±
11.2
9.6
10.2
4.7
15.7
57.5
98.8
67.3
±
±
±
±
2.7
5.5
8.5
5.3
15.7
50.0
99.2
62.8
Pre
Post
Pre
E (n = 10)
C (n = 12)
Table 1
Physiological parameters and percent change obtained in cardiopulmonary exercise testing before and after 24 weeks of training.
%
ER (n = 10)
Post
±
±
±
±
2.9
7.0
6.3
4.3
%
±
±
±
±
19.5
17.7
9.4
5.8
M.G. Santana et al. / Journal of Science and Medicine in Sport 15 (2012) 259–265
and ER groups compared to pre-training values (15.0 and
12.6%, respectively). Moreover, the time to exhaustion was
significantly higher when compared to pre-training values (E:
18.7% and ER: 11.4%).
All participants finished the 6-MWT without difficulty or
premature stop. The 6-MWT performances of the participants are shown in Table 2. The distances completed and,
consequently, the walking speeds were significantly higher
in the E (5.5%) and ER (4.6%) groups when compared to the
pre-training values.
The 24 weeks of resistance training for the ER group significantly increased 1-RM in all eight exercises tested. As
expected, there were no significant alterations in the C and E
groups (Table 3).
In the pre-intervention period (n = 32), the 6-MWT distances correlated positively with the V̇ O2 peak (r = 0.51,
p = 0.001) and V̇ O2 at AT (r = 0.39, p = 0.010). On the other
hand, there was no significant correlation between changes
(after–before) in the distance covered in the 6-MWT and
changes (after–before) in the V̇ O2 peak (E and ER groups:
r = 0.38, p = 0.097).
4. Discussion
The purpose of this study was to determine whether the 6MWT is able to detect changes in the CRF of healthy elderly
men submitted to two modes of exercise programs. Following
24 weeks of a training program performed by the E and ER
groups, there was an increase in V̇ O2 peak and covered distance in the 6-MWT (Table 1). However, these results did not
support our hypothesis that changes in CRF could be detected
by changes in the 6-MWT performance, since there was no
a relationship between the changes (after–before) in CRF
V̇ O2 peak and the 6-MWT performance (covered distance).
The magnitude of increase in V̇ O2 peak was similar
between E and ER groups, 15.1% (4.2 mL kg−1 min−1 )
and 12.7% (4.3 mL kg−1 min−1 ), respectively, even with a
reduced frequency and volume weekly of endurance training
in the ER group. These results provide consistent evidence
that adding strength training to endurance training does not
interfere with CRF development. We also verified that there
was increase muscle in strength in the ER group even with a
reduced frequency and volume weekly of strength training.
As previously observed by Wood et al.23 and Izquierdo et al.24
the reduced volume maybe an important factor in designing
training regimes to performance adaptations with concurrent
training in elderly men.
Physiologically, the increase in V̇ O2 peak (for E and ER
groups) in the current study was higher than 1 Metabolic
Equivalent (1-MET = 3.5 mL kg−1 min−1 ). In a recent metaanalysis, Kodama et al.6 reported that the increase of 1-MET
in CRF is associated with a decrements in risk of all-cause
mortality (13%) and cardiovascular diseases (15%). The
author explained that a increase of 1-MET in CRF is comparable to a 7-cm, 5-mmHg, 88 mg dL−1 , and 18 mg dL−1
decrement in waist circumference, systolic blood pressure,
Table 2
Physiological parameters and percent change obtained in the six-minute walk test before and after 24 weeks of training.
C (n = 12)
Pre
601.5
1.67
24.3
86.5
124.8
83.9
%
Post
±
±
±
±
±
±
61.0
0.17
3.0
11.4
14.9
5.7
580.8
1.61
23.2
83.8
120.8
80.4
±
±
±
±
±
±
35.3
0.10
3.3
13.0
14.2
8.5
−3.0
−3.0
−4.1
−2.9
−2.9
−3.5
Pre
±
±
±
±
±
±
5.9
5.9
10.6
10.7
7.4
9.7
614.2
1.71
24.5
90.3
130.5
88.6
ER (n = 10)
%
Post
±
±
±
±
±
±
59.4
0.16
3.1
9.3
19.0
10.3
646.7
1.80
27.9
88.7
131.9
83.5
±
±
±
±
±
±
57.1 a
0.16 a
5.6 a
9.1
16.8
9.5
5.5
5.5
13.4
−1.4
1.7
−5.1
Pre
±
±
±
±
±
±
5.3 b
5.3 b
12.8 b
9.0
8.5
7.9
640.4
1.78
25.6
88.5
140.5
89.5
%
Post
±
±
±
±
±
±
47.1
0.13
5.2
11.5
17.6
5.2
669.1
1.86
29.8
90.2
143.3
88.7
±
±
±
±
±
±
43.0 a
0.12 a
4.8 a
10.2
13.2
6.4
4.6
4.6
14.3
4.3
3.0
−0.9
±
±
±
±
±
±
2.8 b
2.8 b
10.1 b
22.9
13.2
7.2
±
±
±
±
±
±
±
±
9.7b
29.0b
8.5b,c
19.7b,c
15.8b,c
18.4b,c
34.2b,c
15.2b,c
Data are presented as the mean ± SD. C: control group; E: endurance training group; ER: concurrent training group; V̇ O2 : oxygen uptake; HR: heart rate.
a p < 0.05, post different from pre.
b p < 0.05, significant difference versus the control group.
Table 3
Absolute and percent change in muscle strength after 24 weeks of training.
C
E
Pre
Chest press (lb)
Leg press (lb)
Vertical traction (lb)
Leg curl (lb)
Biceps curl (lb)
Abdominal crunch (lb)
Arm extension (lb)
Lower back (lb)
105.5
266.7
156.2
95.0
55.0
67.9
107.1
105.0
%
Post
±
±
±
±
±
±
±
±
20.9
54.2
22.3
16.4
10.9
17.2
24.1
16.4
109.2
283.0
157.9
94.6
52.1
70.8
105.4
102.9
±
±
±
±
±
±
±
±
21.8
72.8
20.4
17.5
11.8
15.3
19.3
21.8
4.4
6.1
1.4
−0.1
−5.3
5.2
−0.4
−2.6
ER
Pre
±
±
±
±
±
±
±
±
8.9
11.8
6.0
10.4
9.8
8.3
11.1
7.4
95.5
284.0
144.5
91.5
48.0
69.5
99.5
111.0
%
Post
±
±
±
±
±
±
±
±
25.5
106.2
24.7
23.7
16.0
18.3
21.9
24.0
95.0
288
151.5
93.5
48.5
72.0
97.5
107.5
±
±
±
±
±
±
±
±
24.9
101.2
24.3
25.7
9.7
18.4
25.1
24.9
−0.2
3.4
5.2
2.2
5.2
3.9
−1.6
−2.2
Pre
±
±
±
±
±
±
±
±
5.7
16.6
9.8
11.8
17.5
7.4
16.4
15.2
84.0
223.0
148.0
96.5
43.0
65.5
93.5
101.5
%
Post
±
±
±
±
±
±
±
±
7.0
51.2
12.5
18.1
7.5
11.4
22.7
12.7
103.5
307.0
169.0
122.0
61.0
86.0
130
121.5
±
±
±
±
±
±
±
±
8.8a
63.2a
15.5a
17.8a
13.1a
13.7a
23.4a
18.6a
23.5
40.1
14.4
29.1
41.5
32.6
44.2
20.1
M.G. Santana et al. / Journal of Science and Medicine in Sport 15 (2012) 259–265
Distance (m)
Speed (m s−1 )
V̇ O2 (mL kg−1 min−1 )
%V̇ O2 peak
HR (bpm)
%HRmax
E (n = 10)
Data are presented as the mean ± SD. C: control group; E: endurance training group; ER: concurrent training group.
a p < 0.05, post different from pre.
b p < 0.05, significant difference versus the control group.
c p < 0.05, significant difference versus the endurance training group.
263
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M.G. Santana et al. / Journal of Science and Medicine in Sport 15 (2012) 259–265
triglyceride level, and fasting plasma glucose, respectively,
and a 8 mg dL−1 increment in high-density lipoprotein
cholesterol. From the clinical viewpoint, these values may
be considerable.
With regard to the 6-MWT, the distance covered by the
three groups (C, E and ER) before the training period was
greater than that reported in previous studies for participants of a similar age.10,25 To help predict the total distance
walked during the 6-MWT, some researchers established a
reference equation.26 When applying this reference equation, it was revealed that the groups walked about 24% more
than the predicted distance in the pre-evaluation. Additionally, the mean walking speed observed during the 6-MWT
before and after the training program was between 1.61 and
1.86 ms−1 , respectively. These speeds are above the comfortable gait speed27 in healthy adults in the same age group
(1.39 ± 0.02 ms−1 ). This highlights the greater performance
of our participants and consequently explains the greater relative workload (%V̇ O2 peak) found in the 6-MWT, i.e., above
the AT (between 48.6 and 57.5% of V̇ O2 peak).
The improvements observed in the 6-MWT performance
in the E and ER groups were modest (5.5 and 4.6%, respectively), as previously reported by another study28 in a similar
population submitted to a 12-month concurrent training
program. These modest improvements are likely the consequence of a possible “ceiling effect”, which takes into account
that our participants are healthy and did not have functional
limitations, as established by the higher speed obtained during the 6-MWT and normal V̇ O2 peak compared to values
expected for their age and gender.20 In other words, even
if the participant is able to run, due to excellent functional
capacity, 6-MWT specifications only allow that the test be
done walking.
The impact of the health status on the 6-MWT performance was investigated in 165 elderly people. The covered
distance decreased significantly with increasing age and
with worsening health status (corrected for age).29 Patients
with dilated cardiomyopathy were also investigated, and the
results demonstrated that covered distance and V̇ O2 peak
were closely correlated.30 In addition, the authors found a correlation between the 6-MWT covered distance and the New
York Heart Association functional class. Corroborating these
results, other work has found that the 6-MWT test cannot
predict outcomes in patients with a history of heart failure.31
However, when the authors separated patients into those that
covered a distance below 300 m, they found that the 6-MWT
was a useful tool to predict outcomes in the lower-functioning
patients. In contrast, when the distance covered was above
300 m, the 6-MWT was not able detect changes. In our study,
none of the participants walked less than 300 m. Therefore,
in part, this could explain why the 6-MWT was not able to
detect changes in V̇ O2 peak resulting from exercise training. Nonetheless, when we analysed the correlation before
training, we were able to find the classic results reported in
the literature, i.e., a positive correlation between the distance
covered in the 6-MWT and V̇ O2 peak.25,32
There was not a significant correlation between changes in
the 6-MWT performance and changes in V̇ O2 peak obtained
in CPET after the training period. Thus, improvements in
V̇ O2 peak after training could not be detected by improvements in the 6-MWT performance. Our findings are in
contrast with a previous study33 that studied children with
congenital heart disease submitted to an aerobic training
program. Their study found that improvements in CPET variables were correlated with improvements in distance covered
during a 6-MWT. These conflicting results are likely a consequence of the excellent functional capacity of our volunteers
as discussed above.
A possible limitation of this study was the use of a 20 m
corridor to perform the 6-MWT, which induces numerous
laps. This could lead to an underestimation of the covered
distance during the 6-MWT. To verify this limitation, it would
be interesting to conduct other studies using different corridor
lengths in the same population.
5. Conclusion
In conclusion, this study showed that, for healthy elderly
men, the changes in 6-MWT performance and the changes
in CPET measures are not correlated. Thus, the use of the
6-MWT is not appropriate to evaluate improvements in cardiorespiratory parameters resulting from endurance training
or concurrent training. However, the 6-MWT is a notable
tool to evaluate functional capacity improvements due to
exercise programs. Therefore, in healthy elderly people,
the information provided by a 6-MWT should be considered complementary to a CPET, not a replacement for
it.
Practical implications
• The 6-MWT is a simple, useful test to evaluate improvements in functional capacity after exercise training.
• The 6-MWT is not appropriate to evaluate improvements
in CRF of elderly healthy men who have undergone exercise training.
• Although the 6-MWT after exercise training has been sensitive to detect improves in the functional capacity, relevant
to many daily activities, it reflect no improves on CRF as
observed in CPET.
• The CPET and the 6-MWT could be used together in order
to provide a complete physical fitness evaluation of health
men after exercise training.
Acknowledgements
We would like to thank all of the participants who volunteered their time to participate in the study.
M.G. Santana et al. / Journal of Science and Medicine in Sport 15 (2012) 259–265
The authors would like to thank the institutions that made
this manuscript possible: AFIP, FAPESP, CEPID/FAPESP,
CEPE, CEMSA, and FADA/UNIFESP.
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