Download Effectiveness of Individualized Aerobic Training at the Ventilatory

Copyright 1997 by The Genmtological Society of America
Journal ofGenmtologv: BIOLOGICAL SCIENCES
1997. Vol. 52A. No. s! B26O-B266
Effectiveness of Individualized Aerobic Training
at the Ventilatory Threshold in the Elderly
Claudine Fabre, Janick Masse-Biron, Said Ahmaidi, Brigitte Adam, and Christian Prefaut
Laboratory of Interaction Physiology, Hopital A. de Villeneuve, Montpellier, France.
This study was designed to specify whether an individualized training program at the ventilatory threshold in elderly
subjects produces greater training adaptations than a standardized training program performed at 50% of heart
rate reserve. Sixteen subjects participated in the study. Maximal exercise tests were performed on a treadmill before
and after the training program. Eight subjects trained at the ventilatory threshold (ITG) and eight trained at 50% of
heart rate reserve (STG). The mean training heart rate was 129 ± 14.2 bpm and 115 ± 7.9 bpm in the individualized
training group (ITG) and the standardized training group (STG), respectively. The maximal O2 uptake (VOiinax)
was improved significantly by 20% in ITG (within group p < .05), whereas no significant improvement was noted in
STG. The improvement in ITG compared to the nonsignificant change in STG was significant (p < .05). In addition,
submaximal ventilation and heart rate were more decreased in ITG than STG. We conclude that for elderly people
an individualized training program at the level of the ventilatory threshold is significantly more effective in terms of
V02max and submaximal cardiorespiratory adaptations.
E
NDURANCE training has been shown to be an effective method for improving both physical fitness and
health in elderly subjects (Pollock et al., 1976; Shepard,
1988). For decades, the training prescriptions have been
based on percentages of maximal oxygen uptake (%
V0 2 max), maximal heart rate (% HRmax), or heart rate
reserve (% HRr) (Malher et al., 1986). However, Katch et
al. (1978), studying normal healthy elderly subjects, and
Vallet et al. (1997), studying elderly chronic obstructive
pulmonary disease (COPD) patients, showed that at a preselected % HRmax, individual subjects may exercise above
or below their anaerobic threshold and thus exhibit dissimilar responses. Thus, these nonindividualized methods,
based on the relative-percent concept, make it difficult to
evaluate a given individual's exercise stress.
The heart rate recorded at the ventilatory threshold (VT),
described by Wasserman et al. (1973), may be a better basis
for activity prescription than an arbitrary relative-percent
for at least three reasons. First, VT takes into account a
specific level of metabolic stress, resulting in more homogeneous responses to training than an arbitrary percentage
of V02max or HR. Second, VT differs among people as a
function of age, gender, physical fitness, health, etc., in
such a way that training at the VT is in fact individualized.
Third, because VT marks the breakpoint in ventilation, we
can expect, from a ventilatory point of view, a good compliance with the training program — particularly because it
has been observed that VT occurs at the same load level as
the dyspnea threshold (Quantin et al., 1996). We have used
individualized training programs at the VT in asthmatic
children and COPD patients and obtained very good results
(Varray et al., 1991; Ahmaidi et al., 1993; Vallet et al., 1997).
This study was designed to determine whether, in elderly
subjects, an individualized training program (ITG) at the
ventilatory threshold leads to greater training responses
than standardized training programs (STG) performed at
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50% of heart rate reserve (50% HRr). Indeed, the American
College of Sports Medicine (1978) recommends a training
heart rate of 50 to 85% of heart rate reserve. The training
heart rate at 50% HRr was chosen because the elderly subjects were sedentary and had a poor level of conditioning.
METHOD
Subjects. —Twenty-five retirees, 8 men and 17 women,
recruited from the Universite de la Culture Permanente in
Nimes, France, expressed interest in a vigorous walking
program to improve functional capacity and aerobic fitness.
Before admittance to the study, all subjects were evaluated
for their cardiorespiratory health. Subjects having abnormal spirometric data, abnormal 12-lead electrocardiograms
(ECG), a supine blood pressure greater than 165/100 mmHg,
ST segment depression, or significant arrhythmias during
exercise testing were excluded from the study. Three subjects were excluded because of heart disease as shown by
the medical history and physical examination; thus, 22 subjects initially participated in the study. However, of the
original 22 subjects, only 16 completed their training program so that the study ended with each group composed of
eight subjects. Two participants (one in ITG and one in
STG) developed medical problems unrelated to training,
three (two in ITG and one in STG) did not complete the
required number of training sessions, and another subject
(STG) developed an inadequate rise in systolic blood pressure at the final examination (T3). These six subjects were
dropped from the analysis.
Subjects who were on medication for hypertension,
rheumatism, or depression at the time of the first examination maintained the same therapeutic regimen throughout
the study. The subjects (aged 64 ± 6.8 years, range 53-74)
had active life styles, but none had performed any regular
physical training for several years. Their activities — utility
TRAINING AT THE VENTILATORY THRESHOLD
walking, gardening, and mild indoor gymnastics — continued throughout the training program. Participants were,
however, discouraged from performing other vigorous activities during the 12-week program. The anthropometric characteristics and initial cardiorespiratory values are given in
Tables 1 and 3. After the procedures were explained in
detail, all subjects provided written consent.
Spirometry. — The maximum expiratory flow curves
were recorded on a digital spirometer (Datalink Pulmochart, Marne la Vallee, France) in order to record the forced
expiratory volume in one second (FEV,). In addition, we
calculated maximal voluntary ventilation (MVV = FEVi X
35; Gandevia and Hugh-Gions, 1957) and the ratio of maximal exercise ventilation to MVV (% MVV).
Physical measures. — Oxygen consumption (VO2) was
determined using an open circuit technique. The subjects
breathed through a rubber mouthpiece attached to a oneway valve (Warren E. Collins, Braintree, MA) with low
resistance and small dead space (90 ml). Inspiratory airflow was measured continuously during exercise through a
pneumotachograph (Fleich no. 3) and a pressure transducer
(MP45, Validyne Engineering Corp., Worthridge, CA) with
a measuring range of ± 2 cm H2O. The pneumotachograph
was placed on the inspiratory tubing in order to avoid problems due to water vapor. The calibration of the flow module
was accomplished by introducing a calibrated volume of air
at several flow rates. Expired gases were sampled in a mixing chamber (5-1) through a flexible hose dried with CaCl2
and analyzed for O2 with a polarographic analyzer (Godard
Capnographe, Statham, Netherlands) and for CO2 with an
infrared analyzer (Godard Rapox, Statham, Netherlands).
Each gas analyzer was calibrated before and after each test
according to a standard certified commercial gas preparation. The inspiratory air flows and the fraction of expired O2
(FeO2) and CO2 (FeCO2) were measured and computed
from the last 10 breath cycles of every minute. Averages
were established for minute ventilation (VE l.min~' BTBS
[body temperature pressure saturated]), VO2 (l.min"1 STPD
[standard temperature pressure dry]), CO2 production
(VCO2 l.min-1 STPD), respiratory ratio (R), and ventilatory
equivalents for O2 (VE/VO2) and CO2 (VE/VCO2).
During the test each subject's electrocardiogram was followed continuously on a cardioscope (Diascope, Simonsen
and Weel, Copenhagen, Denmark). Electrodes were placed
in the CM5 lead position. The heart rate was also assessed
with a cardiofrequency meter (Sportester PE 3000, Polar
Electro, Kemple, Finland). The arterial pressure was continuously recorded on a tensionmeter (Quinton Q 3000,
Seattle, WA). The maximal oxygen pulse (VO2max/HRmax)
was expressed in ml.bpnr1.
Maximal exercise test. — The test was performed on a
motor-driven treadmill (Gymrol 1800, Roche la Moliere,
France). VO2 was determined using a modified Balke and
Ware (1959) protocol. The speed of the treadmill was individualized from the value of heart rate at rest plus 25 bpm
and remained fixed during testing. During the determination of treadmill speed the subjects familiarized themselves
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with the test procedures. The grade after 3 min of warm-up
was increased by 1.25% every minute until exhaustion. The
observation of three of the four following criteria was necessary to assume that the subjects had reached their
V0 2 max: (J) stability of VO2 in spite of the increase in
work load; (2) stability of HR at a value close to the theoretical maximal HR, i.e., 210-.65 X age ± 10; (3) R > 1.10;
and (4) the inability of the subject to maintain the walking
speed. Before and after each test the accuracy of the treadmill speed was verified by a stopwatch recording of 15
treadmill belt revolutions. After completion of the exercise
test, the VT was determined for each subject by using the
V-slope method of Beaver et al. (1986). This method
involves the analysis of the behavior of VCO2 as a function
of VO2 and assumes that the threshold corresponds to the
break in the linear VCO2-VO2 relationship; indeed, this
threshold is also called the gas exchange threshold (GET)
(Patessio et al., 1993). The reading was effected independently by two experienced investigators. In the rare case of
discordance, the criteria of Wasserman et al. (1973) were
used to reach a consensus or to eliminate the subject. In this
study a consensus was always reached. The difference observed between the two investigators did not exceed 3%.
Protocol. — The subjects were tested before training
(TO) and after a 3-month aerobic training period (T3)
(physical, clinical, and spirometric examination and maximal exercise testing). After the first test, the subjects were
randomized into two groups (each n = 8), and training heart
rate (HRt) was determined. The standardized training group
(STG) trained at the standard level of 50% heart rate
reserve (HRt 50%) equal to 50% X (HRmax - HRrest) +
HRrest. The individualized training group (ITG) trained at
the heart rate corresponding to the gas exchange threshold
(HRt GET). The two groups showed no significant differences concerning age, sex, weight, height (Table 1), HRt
GET, HRt 50% (Table 2), initial V02max (Table 3) and life
style. The subjects did not know which method had been
used to determine their training heart rate.
Training program. — The training program consisted of
interval walking to HRt intensity twice a week on an outdoor
running track under the supervision of study personnel. The
principle of interval training is to alternate between periods
of exercise at the target heart rate and active recovery. An
example of a training session can be seen in Figure 1. Each
session differed in order to maintain high motivation, e.g., in
Session 1 the exercise was presented as 400 m X 8; in
Session 2, 800 m X 4, etc. However, total time spent at the
target heart rate was slowly increased over sessions as subjects progressed with a concomitant reduction in recovery
time. All sessions were preceded by a 10-min warm-up
(stretching and self-massage) and ended with a 10-min cooldown (stretching and relaxation). The interval walking durations progressively increased so that by the end of the training period, subjects were exercising for one full hour. A work
technique (respiratory movements in coordination with walking rhythm, stride length, velocity, etc.) was proposed at each
session. During training, HRt was continuously recorded by
means of a cardiofrequency meter (Sportester PE 3000, Polar
FABRE ETAL.
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Table 1. Anthropometric Characteristics of Standardized
Training Group (STG) and Individualized Training Group (ITG)
Subjects, n
Age,
years
Sex
Height,
cm
Body mass,
kg
STG
1
2
3
4
5
6
7
8
Mean ± SD
63
67
64
57
74
71
62
53
63.9 ± 6.8
F
F
M
F
F
M
M
F
149
152
173
159
145
175
164
144
157.6+ 12.2
46
48
75
56
41
84
73
47
58.7 ±16.4
ITG
1
2
3
4
5
6
7
8
Mean ± SD
65
65
64
57
63
69
57
63
62.9 ± 3.9
F
M
F
F
F
M
M
F
148
182
155
166
157
180
179
161
166 ± 13
59
103
62
48
46
84
87
59
68.5 ± 20.6
n.s.
n.s.
Differences
between groups
n.s.
Note: n.s. = not significant.
Electro, Kemple, Finland). The accuracy of this monitor was
established by comparing its results with the pulse rate monitored with actual ECG recordings during exercise on the
treadmill. The cardiofrequency meter was set in such a way
that subjects could exercise within ± 5 bpm of prescribed
intensity. An alarm sounded when the HR of the subject was
out of the preselected range. After each session, the HRt was
checked from the generated HR curves (Figure 1).
Walking/running tests were periodically performed on a
400 m running track to measure the. walking speed at HRt;
this was done to assess the modifications in submaximal
performance. The first test (Test 1) was conducted after one
month of training, the time deemed necessary for the subjects to achieve a stable HRt. The second test (Test 2) was
performed at the end of the 3-month training period. The
HRt was monitored with data from the Sportester, and the
speed was measured in km.h"1.
Statistical analysis. — The data collected on entry were
compared for homogeneity, HRt at GET and HRt 50%
between the two groups using an unpaired Student's /-test.
The walking speed at HRt measured before and after training
was analyzed by an unpaired Mest on the mean differences.
An analysis of variance (ANOVA), with group as a between-subject factor and time a within-subject factor, was
performed on variables at rest, and at submaximal and maximal intensities. When the ANOVA F ratio was significant
(p < .05), we tested for significant differences in terms of
between-group and within-group effects and Group by
Time interaction.
Table 2. Values of Heart Rate (bpm) Used for Training Intensities
Subjects, n
STG
1
2
3
4
5
6
7
8
M±SD
ITG
1
2
3
4
5
6
7
8
M±SD
HRmax
HR
rest
HR
GET
50% HRr
HRGET
% HRmax
50% HRr
% HR max
154
162
145
165
150
150
160
180
158 ±9.6
80
68
52
68
65
83
90
58
70 ±13
133
125
100
122
131
137
135
134
127 ±12.2
117
115
99
117
108
117
125
120
115 ±7.9
86
77
69
73
87
91
84
74
80 ± 7.9
76
71
68
71
72
78
78
66
73 ±4.5
176
140
160
156
155
178
152
183
162 ± 15
65
71
72
80
70
144
108
134
130
135
128
110
146
129 ±14.2***
120
105
116
118
113
81
77
83
83
87
72
72
81
79 ±5.6
68
75
72
75
72
65
78
80
73 ± 6.2
122
115
132
118 ±7.9
68
75
72
72 ±2.8
Notes: HR = heart rate; HR GET = HR corresponding to the gas exchange threshold; 50% HRr = 50% of HR reserve; HR GET % HRmax = value of
HR GET in % HRmax; 50% HR % HRmax = value of 50% HRr in % HRmax; STG = standardized training group; ITG = individualized training group.
***/; < .001 between HR GET and 50% HRr.
TRAINING AT THE VENTILATORY
Table 3. Cardiorespiratory Responses to Maximal Exercise
and at the Gas Exchange Threshold Before (TO)
and After 3 Months of Training (T3); Means ± SD
STG
ITG
p-value of
Interaction
, l.mirr
TO
T3
1.50 ± 0.53
1.59 ± 0.56
V02max, ml.kg '.min 1
TO
T3
25.45 ± 6.79
26.87 ± 3.96
HRmax, bpm
TO
T3
158 ± 9.60
157 ± 11.31
Peak O2 pulse, ml.bear'
TO
T3
16± 0.02
17± 0.01
1.77 ± 0.79
2.11 ± 0.96**
25.42 ± 5.65
30.63 ± 8.48*
<.O5
162 ± 15
162 ± 8.48
n.s.
16± 0.01
20 ± 0.02*
n.s.
VO2 at GET, ml.kg-'.minTO
T3
15.37 ± 3.68
17.36 ± 2.57*
14.84 ± 3.68
18.96 ± 2.69*
n.s.
GET, % VO2max
TO
T3
61.10 ± 11.88
67.50 ± 7.64
60.50 ± 16.4
63.70 ± 13.01
n.s.
127 ± 12.2
126 ± 8.48
129 ± 14.2
136 ± 11.31
n.s.
HR GET, bpm
T3
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expressed as ± SD. In addition, the 95% confidence interval
is given when helpful. The limit for statistical significance
was always set at p < .05.
RESULTS
Clinical adaptation to training. — Adherence to the
<.O5
1
TO
THRESHOLD
Notes: STG = standardized training group; ITG = individualized training group; VO2max = maximal O2 uptake; HRmax = maximal heart rate;
GET = gas exchange threshold; HR GET = heart rate at GET; n.s. = not
significant.
*p < .05; **p < .01, within group comparison.
Time (minutes)
Figure 1. Example of interval walking program of ITG subject no. 3.
This shows the HR during a training session. Hit = 138 bpm. The exercise
sequences lasted one minute, each followed by one minute of recovery.
This was repeated three times (a) and followed by exercise sequences of 2
minutes with the same recovery, three times (b); and then by 4-minute
sequences, also with one-minute recoveries (c). The session finished with
two exercise sequences of 10 minutes with a 3-minute recovery between
them (d).
The VE and HR kinetics for each subject were calculated
as a function of VO2 using a logarithmic equation of the
relation between these parameters and VO2. The values of
VE and HR were calculated before and after training at
60%, 80%, and 100% of pretraining V02max. The values
are reported as means. Dispersion around mean values is
training programs for the subjects was very good. There
were no injuries or untoward events associated with the
walking program.
The mean of HRt in STG was 115 ± 7.9 bpm (range
99-125). The mean of HRt in ITG was 129 ± 14.2 bpm
(range 108-144). Therefore, HRt at GET was significantly
higher (p between groups < .001). Moreover, HRt was much
more variable in the ITG than in the STG group (Table 2).
After 4 weeks of training, it was necessary for the following subjects — 3, 4, 6 of STG and 5, 7, 8 of ITG — to
alternate walking and jogging in order to train at the exact
HRt. At Test 1 of the 400 m running track test, the walking
speed at HRt was 5.91 km.h-1 (range 4.2-6.8) in STG and
6.07 km.h"1 (range 4.2-7) in ITG. At Test 2, the walking
speed at HRt was 6.02 km.h-1 (range 4.2-6.8) in STG and
6.62 km.rr1 (range 5-7.5) in ITG. The change in walking
speed at HRt (Test 2 - Test 1) was significantly higher in
ITG (0.6 ± 0.08) than in STG (0.1 ± 0.10 km.h-1), with significant differences between groups (p < .01).
Responses at rest. — Before training, the mean HR in
ITG was 70 ± 13; after training, it was reduced, though not
significantly, to 68.7 ± 10.6. In STG, HR was 73 ± 6.2 and
after 3 months of training it was reduced, again not significantly, to 71.8 ± 8.8.
Responses to maximal exercise. — Concerning the
V0 2 max, we noted a greater adaptation after training in
ITG compared to STG, demonstrated by the significant
Group by Time interaction (p < .05). The significant
improvement in V02max was 20% in ITG (p < .05), whereas no significant change appeared in V0 2 max for STG
(Table 3). For this variable, the 95% confidence interval
(CI) of differences between T3-T0 was -.07 to .25 l.min-'
for STG and .11 to .57 l.min-' for ITG. The HRmax was not
statistically different between the two groups initially, and
it remained unchanged after training. We observed a significant increase in maximal O2 pulse in ITG after training (p
within group < .05); there was no significant change in
STG, and the Group by Time interaction was not significant
(Table 3). The VEmax of both ITG and STG was increased
as a function of time during training (p within each group <
.01); thus, the differences between the two groups were not
significant (Table 4). Furthermore, for both groups, no differences were observed in maximal VE/VO2 and MVV
(Table 4). At T3 the % MVV was increased in ITG (p within group < .05) (Table 4).
Responses to submaximal exercise. — VO2 at the GET
was increased in both groups (p within each group < .05) as
a function of training, but the difference between the two
groups was not significant (Table 3).
We assessed VE and HR for the same absolute VO2
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FABRE ETAL.
Table 4. Ventilatory Responses to Maximal Exercise
Before (TO) and After (T3) Training; Means ± SD
/j = 8
ITG
n=8
p-value of
Interaction
VEmax, l.miir1 BTPS
TO
T3
53.6 ± 17.2
55.8 ±16.1**
59.9 ± 11.9
72.9 ± 12.8**
n.s.
VE/VO2
TO
T3
30.9 ± 6.8
31.1 ± 5.6
26.7 ± 6.5
28.0 ± 4.5
n.s.
MVV
TO
T3
76.3 ± 24
75.7 ± 24.3
83.9 ±16.9
73.2 ±28
n.s.
%MVV
TO
T3
72.6 ±21.2
74.8 ± 12.4
69.6 ± 28
81.9 ±25.7*
n.s.
STG
Notes: STG = standardized training group; ITG = individualized training group; VEmax = maximal minute ventilation; VE/VO2 = ventilatory
equivalent for Oy, MVV = maximal voluntary ventilation; % MVV = percentage of MVV; n.s. = not significant.
*p <.O5; **p < .01, within group comparison.
Table 5. Reductions With Training in Ventilation and Heart Rate
STG
n=8
ITG
i
VE
l.min"1
HR
bpm
VE
l.min"1
HR
bpm
-2.0 ± 3.7
n.s.
- 6 ± 5.6
p<.05
-8.3 ± 9.6
- 1 4 ± 11 .3
80%
-0.3 ±5.1
n.s.
- 5 ± 11.3
n.s.
-7.5 ±11.9
n.s.
-14± 14 .1
p < .05
100%
-4.9 ± 13
n.s.
- 4 ± 5.6
n.s.
-12.1 ± 18.1
n.s.
-14± 11 .3
p<.0\
%V0 2 maxatTO
60%
p<.05
p<.0\
Notes: STG = standardized training group; ITG = individualized training group; TO = before training; T3 = 3 months after training; VE =
minute ventilation; HR = heart rate; % VO2max = percentage of the maximal oxygen uptake; n.s. = not significant. Values ± SD represent changes
in VE and HR from TO to T3, measured at 60, 80, and 100% of the initial
V0 2 max(V0 2 maxatTO).
(60%, 80%, and 100% of pretraining VO2max) by the delta
values between TO and T3. For these levels, the modifications were slight and not significant in STG except for HR
at 60% of V02max, which was decreased by 6 ± 5.6 bpm (p
within group < .05). In ITG, the decrease in VE was marked
and significant at 60% of VO2max (35% reduction in VE, p
within group < .05). The HR in ITG was systematically
decreased at 60%, 80%, and 100% of V02max, for/? within
group < .01,/? < .05, and/? < .01, respectively (Table 5).
Individualized training at 50% heart rate reserve. — In
three subjects of ITG, the HRt GET was, in fact, at 50% of
their heart rate reserve (subjects 2, 6, and 7). In two subjects of STG, HRt 50% was at the level of HRt GET (subjects 3 and 4). Therefore, in five subjects, the training was
conducted at a HRt GET which was, in fact, at 50% of
heart rate reserve (113.6 ± 11.3 bpm vs 116.6 ± 9.4 bpm).
In these five subjects, VO2max increased from 2.29 ± 0.73
l.min 1 at TO to 2.51 ± 1.00 l.min 1 at T3, an increase
of 10%.
DISCUSSION
This study indicates that an individualized training program at the ventilatory threshold (determined in terms of
gas exchange threshold) is very well tolerated by the sedentary elderly even if it is conducted at a higher heart rate
than a standardized program at the level of 50% of heart
rate reserve. Because it is conducted at a higher intensity,
the individualized program is significantly more effective
than the standardized program in terms of improving
V02max and submaximal cardiorespiratory adaptations.
The training intensity was not readjusted at midpoint in
the program. Indeed, it is possible that GET would have
increased and HR would have decreased. However, the
decrease in resting HR was not significant after training,
and Vallet et al. (1994) showed that HR at GET after one
and two months of aerobic training was not modified in
spite of an increase in GET in COPD patients. Therefore,
we assume that the effect of this absence of readjusted
training intensity was minor.
In the literature, there are no cardiorespiratory differences
reported at rest (VO2, HR, VE) between young sedentary
and older sedentary people (De Vries and Adams, 1972;
Heath et al., 1981; Levy et al., 1993); however, differences
have been noted during exercise. VE and ventilatory equivalent for O2 (VE/VO2) are greater in older sedentary subjects
compared to young subjects (De Vries and Adams, 1972) for
all work levels. Inbar et al. (1994) demonstrated that for an
intensity below 50% of VO2, aging did not influence the
cardiorespiratory responses to exercise, but that after this
load it did. The variables studied by Inbar et al. (1994) were
VCO2, HR, O2 pulse, VE, Vt, and f. By aerobic training at a
standardized intensity, elderly subjects can reduce hyperventilation and VE/VO2 during submaximal exercise and
increase their GET (Yerg et al., 1985; Makrides et al., 1990;
Poulin et al., 1992). The present study showed that with an
individualized training program the adaptations of these different variables are better than with a standardized intensity
during the same period of training. This phenomenon was
also observed in COPD patients who followed either an
individualized program at the GET or a standardized training program (Vallet et al., 1997).
It is well known that endurance exercise training in
elderly persons can elicit sizable increases in V02max, as it
does in younger individuals (Seals et al., 1984; Hagberg et
al., 1989; Makrides et al., 1990). The improvement in
V02max as reported in the literature has ranged from 7 to
38% (Sidney and Shepard, 1978; Badenhop et al., 1983;
Seals et al., 1984; Thomas et al., 1985; Yerg et al., 1985;
Blumenthal et al., 1989; Hagberg et al., 1989; Makrides et
al., 1990; Masse-Biron et al., 1990; Blumenthal et al.,
1991), and this emphasizes the need to optimize the training programs. The discrepancies observed may be due to
differences in duration, intensity, or frequency of training.
Since the late 1980s it has been recognized that prolonged
endurance exercise training can elicit substantial cardiores-
TRAINING AT THE VENTILATORY THRESHOLD
piratory adaptations even in men and women in their 70s
(Hagberg et al., 1989). The exact role of intensity, however,
is not yet well understood. Preselected percentages of
V02max, HRmax, and HRr are usually used to determine
the intensity, although as early as 1978, Katch et al. showed
that at a preselected percentage of HRmax, subjects may
exercise above or below their GET. During work at 80%
HRmax, for example, half of their subjects remained below
their GET and exhibited fewer training responses. Therefore, programs using prescriptions based on the relativepercent concept may create multiple training stimuli among
the participants, which in turn results in a wide range of
improvement in cardiorespiratory and metabolic functions
(Dwnyer and Bybee, 1983). This observation suggests that
an exercise intensity based on the relative-percent concept
may have limited usefulness in ensuring that a desired level
of metabolic stress is attained for all subjects. The assumed
relation of GET to fuel use and lactate accumulation indicates that its use in training prescriptions may define a better metabolic level and more precise training stimuli.
Moreover, individualization of training intensity can maximize compliance to the training program.
To our knowledge, exercise in the elderly has been prescribed on the basis of anaerobic threshold only in three
studies. However, in the first investigation, Belman and
Gaesser (1991) did not train their subjects at the level of
lactate threshold but at an intensity above this threshold.
Takeshima et al. (1993) trained elderly subjects at the
anaerobic threshold and showed an improvement in
V02max of about 10%. Last, the exercise intensity was also
at the anaerobic threshold in the study of Motoyama et al.
(1995), but no cardiorespiratory parameters were studied.
We chose to compare individualized training at the GET
to a standardized training program performed at 50% of
heart rate reserve. Indeed, the American College of Sports
Medicine (1978) recommends a general range of training
intensities from 50-85% of heart rate reserve, but insists on
the importance of starting sedentary subjects at 50% of
HRr, which is usually done (Badenhop et al., 1983; Seals
et al., 1984; Yerg et al., 1985; Blumenthal et al., 1991; Levy
et al., 1993). As the GET in our study was at 60% HRr, we
in fact compared training programs at two levels of intensity in sedentary elderly subjects, the highest intensity
being also based on the principle of individualization.
Whatever the training intensity, training programs were
clinically very well tolerated, and subjects of both groups
expressed the same enthusiasm for the various exercise
components.
Previous studies have generally shown that in the elderly,
high-intensity training elicits greater increases in aerobic
capacity than low-intensity training (Sidney and Shepard,
1978; Seals et al., 1984; Makrides et al., 1990; MasseBiron et al., 1990). According to these studies, the difference in the improvement in V0 2 max that we recorded
between the two groups was first due to the difference in
training intensity. Whether the specific metabolic level and
the individualization of training enhanced the improvement
of V02max in ITG is difficult to assess in our study. However, in those five subjects in whom GET was at 50% of
HRr, the improvement in V02max was 10% (versus 6% in
B265
the entire 50% HRt group), suggesting that individualized
training is more effective; this finding must be confirmed
by further studies. The 20% increase in VO2max observed
in the ITG group is in the middle range of improvements
for this parameter, as reported by previous studies (Sidney
and Shepard, 1978; Yerg et al., 1985; Hagberg et al., 1989;
Masse-Biron et al., 1990). The STG group, on the contrary,
corresponded to a low-intensity training group with a
slight, but nonsignificant, change in V02max (6%). The
95% confidence intervals calculated for V0 2 max were
equivalent; thus, the nonsignificant VO2max change in STG
cannot be due to excessive heterogeneity in this group. The
data of Belman and Gaesser (1991) showed different
results. By training elderly subjects at intensities above and
below the lactate threshold, they observed in both groups a
small increase (7%) in VO2max. Their high-intensity group
was trained at a heart rate very close to that of our ITG
group. The small improvement in their V02max could be
explained by a shorter program (8 vs 12 weeks), and most
likely by their using a 30-min continuous training program
versus a progressively increased interval training program.
This observation is also true for the study of Takeshima et
al. (1993), who used the anaerobic threshold for the intensity of exercise but observed only an improvement of 10%
in V02max. Indeed, an interval training program seems to
be more effective. Makrides et al. (1990) showed a 38% increase in peak O2 with interval training consisting of
repeated 5-min bouts of high-intensity exercise (140 bpm,
85% of peak VO2) separated by recovery periods at a lower
intensity (65% of peak VO2). It is more difficult to explain
why the low-intensity training of Belman and Gaesser
(1991) was just as effective as their high-intensity training
in improving V02max.
An important difference between our two groups was the
dispersion of the training heart rate. In the ITG group the
mean HRt was 129 bpm and the standard deviation was
14.2 bpm. In the group trained at 50% HRr these values
were, respectively, 115 and 7.9 bpm. In the ITG, the standard deviation of the mean of the training heart rate was
therefore almost twice that of the 50% HRr group. Such a
large inter-individual difference in HRt in the former group
is very much consistent with the notion of individualized
training.
Training effectiveness is usually evaluated in terms of
V02max. However, the aims of training programs are not
only to increase aerobic capacity. In our experience, it is at
least as important to improve exercise tolerance at submaximal levels. In the STG group, we observed only a small
decrease in heart rate (-6 bpm), consistent with the decrease reported by Hagberg et al. (1989) for subjects
trained at the same intensity. In the ITG group, we observed
a significant decrease in heart rate (-14 bpm) at each submaximal level with a less substantial change in VE, smaller
than that described by Makrides et al. (1990). The shift to
the right of GET in both groups indicates a better O2 delivery to the contracting muscles and/or reduced diffusion distance from capillary to mitochondria, which is consistent
with the post-training reduction in lactacidemia in the
elderly that we have previously described (Masse'-Biron et
al., 1992). The dissociation in both groups between the
B266
FABRE ETAL.
uniform improvement of GET and the non-uniform improvement in V02max is consistent with the idea that the
mechanisms responsible for these improvements are probably dissociated (Belman and Gaesser, 1991).
In 1985, Cunningham et al. suggested that because the
VT occurs at a relatively high percentage of V02max in the
elderly, the use of % V02max as a guide for exercise prescription in this population may underestimate the necessary stimulus for inducing a training effect. The present
results support this hypothesis and show that using the VT,
an individualized variable, as a guide for exercise prescription induces improvements in aerobic capacity and in submaximal exercise tolerance.
Although individualized training programs seem to be
very effective for the elderly, they are difficult to prescribe
on a large scale because of current difficulties in conducting
exercise tests for every applicant. Therefore, standardized
training programs may remain useful. In this case, our
results have clearly demonstrated that 50% HRr is too low
a training intensity and that using 60% HRr should be a
better basis for standardized training programs in healthy
elderly subjects.
ACKNOWLEDGMENTS
This work was supported by INSERM Grant 931102.
Address correspondence to Dr. Claudine Fabre, Laboratoire de
Physiologie des Interactions, Service d'Exploration de la Fonction
Respiratoire, Hopital A. de Villeneuve, 34295 Montpellier, Cedex 5,
France. E-mail: [email protected]
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Received July 22, 1996
Accepted May 1, 1997