Dose-response relationship of endurance training for autonomic circulatory control in healthy seniors

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DOI: 10.1152/japplphysiol.00085.2005 · Source: PubMed
Abstract
Aging results in marked abnormalities of cardiovascular regulation. Regular exercise can improve many of these age-related abnormalities. However, it remains unclear how much exercise is optimal to achieve this improvement or whether the elderly can ever improve autonomic control by exercise training to a degree similar to that observed in healthy young individuals. Ten healthy sedentary seniors [71 +/- 3 (SD) yr] trained for 12 mo; training involved progressive increases in volume and intensity. Static hemodynamics were measured, and R-wave-R-wave interval (RRI), beat-to-beat blood pressure (BP) variability, and transfer function gain between systolic BP and RRI were calculated at baseline and every 3 mo during training. Data were compared with those obtained in 12 Masters athletes (68 +/- 3 yr) and 11 healthy sedentary young individuals (29 +/- 6 yr) at baseline. Additionally, the adaptation of these variables after completion of identical training loads was compared between the seniors and the young. Indexes of RRI variability and baroreflex gain were decreased in the sedentary seniors but preserved in the Masters athletes compared with the young at baseline. With training in the seniors, baroreflex gain and resting BP showed a peak adaptation after moderate doses of training following 3-6 mo. Indexes of RRI variability continued to improve with increasing doses of training and increased to the same magnitude as the young at baseline after heavy doses of training for 12 mo; however, baroreflex gain never achieved values equivalent to the young at baseline, even after a year of training. The magnitude of the adaptation of these variables to identical training loads was similar (no interaction effects of age x training) between the seniors and the young. Thus RRI variability in seniors improves with increasing "dose" of exercise over 1 yr of training. In contrast, more moderate doses of training for 3-6 mo may optimally improve baroreflex sensitivity, associated with a modest hypotensive effect; however, higher doses of training do not lead to greater enhancement of these changes. Seniors retain a similar degree of "trainability" as young subjects for cardiac autonomic function to dynamic exercise.
Dose-response relationship of endurance training for autonomic circulatory
control in healthy seniors
Kazunobu Okazaki, Ken-ichi Iwasaki, Anand Prasad, M. Dean Palmer, Emily R. Martini,
Qi Fu, Armin Arbab-Zadeh, Rong Zhang, and Benjamin D. Levine
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas,
and University of Texas Southwestern Medical Center, Dallas, Texas
Submitted 25 January 2005; accepted in final form 9 May 2005
Okazaki, Kazunobu, Ken-ichi Iwasaki, Anand Prasad, M.
Dean Palmer, Emily R. Martini, Qi Fu, Armin Arbab-Zadeh,
Rong Zhang, and Benjamin D. Levine. Dose-response relationship
of endurance training for autonomic circulatory control in healthy
seniors. J Appl Physiol 99: 1041–1049, 2005. First published May 12,
2005; doi:10.1152/japplphysiol.00085.2005.—Aging results in marked
abnormalities of cardiovascular regulation. Regular exercise can improve
many of these age-related abnormalities. However, it remains unclear
how much exercise is optimal to achieve this improvement or whether
the elderly can ever improve autonomic control by exercise training to
a degree similar to that observed in healthy young individuals. Ten
healthy sedentary seniors [71 3 (SD) yr] trained for 12 mo; training
involved progressive increases in volume and intensity. Static hemo-
dynamics were measured, and R-wave-R-wave interval (RRI), beat-
to-beat blood pressure (BP) variability, and transfer function gain
between systolic BP and RRI were calculated at baseline and every 3
mo during training. Data were compared with those obtained in 12
Masters athletes (68 3 yr) and 11 healthy sedentary young individ-
uals (29 6 yr) at baseline. Additionally, the adaptation of these
variables after completion of identical training loads was compared
between the seniors and the young. Indexes of RRI variability and
baroreflex gain were decreased in the sedentary seniors but preserved
in the Masters athletes compared with the young at baseline. With
training in the seniors, baroreflex gain and resting BP showed a peak
adaptation after moderate doses of training following 3– 6 mo. Indexes
of RRI variability continued to improve with increasing doses of
training and increased to the same magnitude as the young at baseline
after heavy doses of training for 12 mo; however, baroreflex gain
never achieved values equivalent to the young at baseline, even after
a year of training. The magnitude of the adaptation of these variables
to identical training loads was similar (no interaction effects of age
training) between the seniors and the young. Thus RRI variability in
seniors improves with increasing “dose” of exercise over 1 yr of
training. In contrast, more moderate doses of training for 3– 6 mo may
optimally improve baroreflex sensitivity, associated with a modest
hypotensive effect; however, higher doses of training do not lead to
greater enhancement of these changes. Seniors retain a similar degree
of “trainability” as young subjects for cardiac autonomic function to
dynamic exercise.
aging; autonomic nervous system; blood pressure
THE MORBIDITY AND MORTALITY of cardiovascular disease in-
crease steeply with advancing age (24). The potential mecha-
nisms for the age-related increase in cardiovascular risk may
include increased blood pressure (BP) (24, 34) and impaired
autonomic control of the circulation with aging (7, 10, 11, 27,
32, 41). There is substantial evidence that elevated BP and
impaired cardiac autonomic function, which is manifest by
decreased heart rate (HR) variability (HRV) and arterial
baroreflex sensitivity, are associated with this increasing car-
diovascular risk (17, 24, 34) and are independent predictors of
cardiac events and overall mortality in clinically disease-free
individuals (15, 48).
Regular physical activity, on the other hand, is known to
prevent or even improve the age-related abnormalities of BP
(18, 34) and cardiac autonomic function (27, 33, 38, 39, 43)
and, thereby, may ameliorate the increasing cardiovascular risk
with aging (8, 11, 20). However, the optimal “dose” of exercise
required to achieve maximal improvement in these variables is
unclear. Recently, our laboratory reported in healthy young
subjects that the peak improvement in indexes of cardiovascu-
lar variability, along with a modest hypotensive effect due to
systemic vasodilation, were observed after moderate doses of
training achieved in 3– 6 mo, but more intense and prolonged
training over 9 –12 mo did not lead to greater enhancement of
these changes (22). We hypothesized that sedentary senior
individuals who begin with depressed HRV and baroreflex
sensitivity may have an even greater degree of “trainability” as
young individuals for the cardiovascular adaptation to exercise.
To test this hypothesis, we quantified the dose-response rela-
tionship between exercise duration/intensity and the adaptation
of BP and cardiac autonomic function in healthy but initially
sedentary seniors. Data were compared with those obtained in
healthy sedentary young individuals and Masters athletes who
had trained for decades to determine whether and how much
exercise training is required to restore the age-related abnor-
malities. In addition, the adaptation of these variables in
sedentary seniors was compared with young subjects after
completion of identical training loads.
METHODS
Subjects population. Ten healthy but initially sedentary senior
subjects older than 65 yr of age (4 women, 6 men; age, 71 3 yr;
mean SD; all Caucasian), and 12 age-matched Masters athletes (6
women, 6 men; age, 68 3 yr; all Caucasian) were recruited.
Sedentary participants were excluded if they were exercising for 30
min, three times per week. Masters athletes were recruited as previ-
ously reported (3). They had participated in regular endurance com-
petitions for 23 8 yr, with a weekly running mileage of 32 10
miles or equivalent swimming or cycling. In addition, 11 healthy
sedentary young subjects (5 women, 6 men; age, 29 6 yr; all
Caucasian), who were reported previously from our laboratory with
regard to cardiovascular adaptation to 1-yr endurance training (22),
Address for reprint requests and other correspondence: B. D. Levine,
Institute for Exercise and Environmental Medicine, 7232 Greenville Ave.,
Suite 435, Dallas, TX 75231 (e-mail: BenjaminLevine@TexasHealth.org).
The costs of publication of this article were defrayed in part by the payment
of page charges. The article must therefore be hereby marked advertisement
in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
J Appl Physiol 99: 1041–1049, 2005.
First published May 12, 2005; doi:10.1152/japplphysiol.00085.2005.
8750-7587/05 $8.00 Copyright
©
2005 the American Physiological Societyhttp://www. jap.org 1041
according to the same standards and criteria, were used for compar-
ison. All subjects were carefully screened for comorbidities, including
systemic hypertension, obstructive coronary artery disease, or struc-
tural heart disease by use of 24-h BP recordings, resting and exercise
ECG, and echocardiograms. Exclusion criteria included mean daytime
BP 140/90 mmHg, ECG changes suggestive of ischemic heart
disease, left bundle branch block, atrial flutter/fibrillation, atrioven-
tricular block greater than first degree, depressed systolic function,
baseline or exercise-induced wall motion abnormalities, valvular heart
disease other than mild valvular insufficiency, right or left ventricular
hypertrophy by ECG or echocardiograms, untreated thyroid disorders,
chronic lung disease, regular cigarette smoking within the previous 10
yr, body mass index 30 kg/m
2
, cardiovascular medications, and
anticoagulation with warfarin. All subjects signed an informed con-
sent form for this study, which was approved by the Institutional
Review Boards of the University of Texas Southwestern Medical
Center at Dallas and Presbyterian Hospital of Dallas.
Exercise training. The sedentary seniors and the young controls
exercised in accordance with a training program prescribed individ-
ually for each subject with the goal of increasing duration and
intensity over 1 yr. Each quarter (Q) was periodized with gradually
increasing stress. Workouts were varied with respect to mode (walk,
run, cycle, swim), duration, and intensity to optimize the training
response. Table 1 is a template of workouts prescribed over the 1-yr
training program for the sedentary seniors. A template of workouts for
the young controls was reported previously (22). Because the seden-
tary seniors had a lower exercise capacity than the young controls at
baseline, the workouts prescribed in each month for the sedentary
seniors were lower in intensity and less in duration than those for the
young controls, to reduce the risk of injury. The training programs for
Q2 and Q4 in the sedentary seniors were designed to be identical to
those for Q1 and Q2 in the young controls, respectively. On the basis
of the HR measured at maximal steady state (MSS) estimated from
ventilatory threshold and the maximal HR (HR
max
) during a maximal
exercise test performed before and every 3 mo of training (see
Maximal exercise test section), five training zones (recovery, base
pace, MSS, race pace, and intervals) were determined. The target HR
for the MSS was set at 5 beats/min of the HR at MSS, which was
generally equivalent to 85–90% of HR
max
. The target HR for the
base pace was set within 20 beats/min below the lower limit of the
MSS range, which was equivalent to 75– 85% of HR
max
. The target
HR for the intervals was set within 5–10 beats/min below the HR
max
.
The target HR for the race pace was set as the difference between the
MSS and the interval range. The majority of training sessions, par-
ticularly during the early phase of the program, were prescribed as
“base pace.” Initially, the sedentary seniors performed at the base
pace, 3 times/wk for 25 min/session, by walking. As the subjects
became fitter, the duration of the base pace sessions was gradually
prolonged, including the addition of one “long-distance” session per
week. Subsequently, high-intensity sessions, including “MSS” and
“intervals,” were added gradually and were always followed by a
“recovery” session. Each subject also performed 10 min of light
exercise and some stretching exercise before and after the main
workout as a warm-up and a cool-down. All of the training sessions
were supervised closely by exercise physiologists. Training mode,
intensity (zone), and duration for every training session were docu-
mented strictly for each subject. Also, HR was monitored and mea-
sured during every training session using a HR monitor (Polar Van-
tage XL, Kempele, Finland). Files from the HR monitor were down-
loaded, and the training progress was evaluated weekly. To quantify
the training stimulus, we used the method of Banister et al. (5) for the
calculation of the training impulse (TRIMP) (Fig. 1). This method
multiplies the duration of a training session by the average HR
achieved during that session, weighted for exercise intensity (5).
Maximal exercise test. A modified Astrand-Saltin incremental
treadmill protocol was used to determine peak exercise capacity (4).
Subjects walked or jogged at a constant speed, which was determined
based on the individual subjects’ fitness to achieve a peak work rate
at 10 –12 min; the grade was subsequently increased by 2% every 2
Table 1. Template of workouts prescribed over a 1-yr training and achieved monthly TRIMP for sedentary seniors
Month Long Distance Base Pace MSS Intervals* Monthly TRIMP
1st 15 @ 25 min 400148
2nd 15 @ 30 min 496236
3rd 15 @ 33 min 30 min 621287
4th 15 @ 35 min 30 min 735415
5th 15 @ 35 min 2 @ 30 min 806416
6th 15 @ 40 min 2 @ 30 min 953489
7th 12 @ 40 min 30 min 3 @ 8 (30 s “on” 90 s “off”) 971407
8th 4@45min 3@35minand4@40min 2@30min 3@8 (45 s “on” 75 s “off”) 1,058330
9th 4@50min 4@35minand4@40min 2@30min 4@8 (60 s “on” 60 s “off”) 1,123519
10th 4 @ 50 min 5 @ 35 min and7@40min 2@30min 4@8 (60 s “on” 60 s “off”) 1,244617
11th 4 @ 55 min 12 @ 45 min 2 @ 30 min 4 @ 8 (60 s “on” 60 s “off”) 1,256619
12th 4 @ 60 min 12 @ 45 min 2 @ 30 min 4 @ 8 (75 s “on” 45 s “off”) 1,265585
Monthly training impulses (TRIMP) are means SD for sedentary seniors, n 10. Target heart rate (HR) for maximal steady state (MSS) is set at 5
beats/min of the measured HR at MSS during maximal exercise test. Target HR for base pace and long distance is set within 20 beats/min below the lower limit
of the MSS range. Target HR for intervals is set within 5–10 beats/min below maximal HR during maximal exercise test. *All interval sessions were followed
by a recovery day, usually consisting of 20–30 min of walking. The workouts in the 6th and 12th mo for sedentary seniors are similar to the workouts in 3rd
and 6th mo for young controls, who are reported previously (22).
Fig. 1. Intensity and duration of training, as quantified by the monthly training
impulse (TRIMP) index during 12 mo of training for sedentary seniors (F).
Data (means SE) are shown with monthly TRIMP during first 6 mo of 1-yr
training for young controls (22). Arrows indicate when experiments were
performed (young controls: before and 3 and 6 mo after training; sedentary
seniors: before and 3, 6, 9, and 12 mo after training). Dashed arrows indicate
when the age effects on cardiovascular adaptation to training were compared
between the sedentary seniors and the young controls.
1042 AGE, EXERCISE, AND HEART RATE VARIABILITY
J Appl Physiol VOL 99 SEPTEMBER 2005 www.jap.org
min until exhaustion. Measures of ventilatory gas exchange were
made by using the Douglas bag technique. Gas fractions were ana-
lyzed by mass spectrometry (Marquette MGA1100), and ventilatory
volume was measured using a Tissot spirometer. HR was monitored
continuously via ECG. Maximal oxygen uptake (V
˙
O
2 max
) was defined
as the highest oxygen uptake (V
˙
O
2
) measured from at least a 40-s
Douglas bag. The criteria to confirm that V
˙
O
2 max
was achieved
included an increase in V
˙
O
2
150 ml, despite increasing work rate of
2% grade; a respiratory exchange ratio 1.1; and HR within 5
beats/min of age-predicted maximal values. In all cases, at least two
of these criteria were achieved.
During the maximal exercise test, breath-by-breath ventilatory
gas-exchange variables were calculated from gas fractions measured
at the mouth by mass spectrometry (Marquette MGA1100) and
minute ventilation (V
˙
E) measured by a turbine flowmeter (VMM,
Interface Associates) and were displayed online. The ventilatory
threshold for all tests was determined by a single, blinded observer
during simultaneous examination of multiple plots of V
˙
O
2
vs. V
˙
E,V
˙
O
2
vs. V
˙
E/V
˙
O
2
,V
˙
O
2
vs. CO
2
production (V
˙
CO
2
), and V
˙
O
2
vs. V
˙
E/V
˙
CO
2
by
using commercial software (First Breath, Marquette). The HR at the
work rate where the ventilatory threshold was observed was identified
as the HR at MSS.
Protocol. Experiments were performed at baseline for all groups,
and 3, 6, 9, and 12 mo after the start of training program for the
sedentary seniors and the young controls. Studies were performed in
the morning at least 2 h after a light breakfast and 12 h after the last
caffeinated or alcoholic beverage was consumed, in a quiet environ-
mentally controlled laboratory with an ambient temperature of 25°C,
after at least 30 min of quiet rest in the supine position. No high-
intensity training sessions were allowed within 72 h of testing,
although easy base pace exercise was allowed up to 24 h before the
study. An analog ECG was obtained, and beat-by-beat arterial BP was
obtained at the finger by photoplethysmography (Finapres, Ohmeda)
at heart level. Intermittent BP was measured in the arm by electro-
sphygmomanometry (Suntech) with a microphone over the brachial
artery and the detection of Korotkoff sounds gated to the ECG.
Cardiac output (CO) was measured with a modification of the foreign
gas rebreathing method by using acetylene as the soluble and helium
as the insoluble gas (47). Stroke volume (SV) and total peripheral
resistance (TPR) were calculated from CO, HR, and BP (electro-
sphygmomanometry) measured at the same time. After the establish-
ment of resting hemodynamic steady state (30 min of repeated
measurements until sequential CO measurements were within 500
ml), 6 min of data, including beat-by-beat arterial BP and ECG, were
recorded during spontaneous respiration. Respiratory rate and tidal
volume were monitored by a turbine flowmeter (VMM, Interface
Associates). Subjects were then asked to control their respiratory
frequency at a fixed rate of 12 breaths/min (0.2 Hz) by following a
graph on a computer. After a 2-min adjustment period, 6 min of data
were recorded again for the controlled respiration data collection
period. The data from the spontaneous respiration protocol were used
to determine mean values for HR, R-wave-R-wave intervals (RRI),
systolic BP (SBP), diastolic BP (DBP), and respiratory rate, and the
data from both the spontaneous and the fixed respiration protocol were
used for spectral and transfer function analysis.
Spectral and transfer function analysis. The analog ECG and
arterial BP were sampled simultaneously at 1 kHz, digitized at 12 bits
(Metrabyte, DAS-20), and analyzed as previously reported (22, 23).
Briefly, the beat-to-beat values of RRI, HR, and SBP were obtained by
using a custom program for peak detection and were linearly inter-
polated and resampled at 2 Hz to create an equidistant time series for
spectral and transfer function estimation (1). The time series of RRI,
HR, and SBP were first detrended with third-order polynominal fitting
and then subdivided into 128-point segments with 50% overlap.
Fast-Fourier transforms were implemented within each Hanning-
windowed data segment and then averaged to calculate the autospec-
tra of RRI and SBP (Fig. 2). The low-frequency (LF, 0.05– 0.15 Hz)
and high-frequency (HF, 0.15– 0.30 Hz) power of RRI (LFRR and
HFRR, respectively) and SBP (LFBP and HFBP, respectively) were
calculated from the integration of the autospectra. These values at
each specific frequency range were also normalized by dividing by the
total spectral power (30). This data acquisition and processing strategy
conforms to consensus panel recommendations for the assessment of
cardiovascular variability (2). The transfer function gain, phase, and
coherence between SBP and RRI were estimated by using the cross-
spectral method (23, 37). The LF and HF transfer function gain
(GainLF and GainHF, respectively), phase, and coherence were esti-
mated as mean values in the same frequency range as above. The
transfer function gain between changes in the SBP and RRI was used
to reflect baroreflex sensitivity (37), whereas the estimated phase was
used to reflect the time relationship between these two variables (37).
The assumption of linearity and reliability of the transfer function
estimation was evaluated by the coherence. In addition, standard
deviation of RRI (SDRR) was calculated.
Statistics. Numerical data are presented as means SD, except
for graphics, in which the SE of the mean is used. In the sedentary
seniors, the effects of each quarter of training were determined by
using one-way repeated-measures ANOVA. The effects of age and
identical training loads were determined by using two-way repeated-
measures ANOVA. Differences in variables among groups were
determined by using one-way ANOVA. Student-Newman-Keuls
method was used for multiple comparisons during post hoc testing.
To express the dose-response relationship between the exercise
stimulus and changes in variables, correlations between the
monthly TRIMP and variables at the baseline, 3, 6, 9, and 12 mo
were estimated from a second-order regression. A P value of
0.05 was considered statistically significant. All analyses were
performed with a personal computer-based analysis system (Sig-
maStat 3.00, SPSS).
RESULTS
Monthly TRIMP during 1 yr of training for the sedentary
seniors is shown in Table 1 and also in Fig. 1 with monthly
Fig. 2. A–C: representative frequency-domain analysis of changes in systolic
blood pressure (SBP) and R-wave-R-wave interval (RRI) in a sedentary senior
subject before (Pre) and after (Post) 12 mo of training. D–F: values obtained
from a young individual before and after 6 mo of training. A and D: power
spectral density (PSD) of SBP. B and E: PSD of RRI. C and F: transfer
function gain between SBP and RRI.
1043AGE, EXERCISE, AND HEART RATE VARIABILITY
J Appl Physiol VOL 99 SEPTEMBER 2005 www.jap.org
TRIMP during the first 6 mo of 1-yr training for the young
controls (22). Monthly TRIMP for both groups steadily in-
creased during the training periods. For the sedentary seniors,
monthly TRIMP at 6 mo was above 930, which is equivalent
to the monthly TRIMP typically observed in a traditional
cardiac rehabilitation program (75% HR
max
, 140 min/wk).
Monthly TRIMP at 12 mo was 1,300, which was approxi-
mately equivalent to training at 75% HR
max
, 200 min/wk.
By design, monthly TRIMP at 6 (953 489) and 12 mo
(1,265 585) for the sedentary seniors was not different from
that at 3 (1,061 388) and 6 mo (1,558 364) for the young
controls, respectively (P 0.579 and 0.151). Cumulative
TRIMP from 4 to 6 mo (Q2; 2,493 1,294) and 10 to 12 mo
(Q4; 3,764 1,762) for the sedentary seniors was not different
from that between 1 and 3 mo (Q1; 2,601 938) and 4 and 6
mo (Q2; 4,672 1,015) for the young controls, respectively
(P 0.829 and 0.159). Therefore, the age effects on cardio-
vascular adaptation to training were compared between the
sedentary seniors and the young controls after “moderate” (6
mo for the sedentary seniors, 3 mo for the young controls) and
“heavy” (12 mo for the sedentary seniors, 6 mo for the young
controls) training. For the purposes of this study, moderate
training was approximately equivalent to training at 75%
HR
max
, 150 min/wk, which is the amount of training cur
-
rently recommended by national organizations for cardiovas-
cular health and fitness (46); heavy training was 25% more
volume (approximately equivalent to training at 75% HR
max
,
200 min/wk) with the addition of interval sessions and
achieves the amount of training associated with the maximal
protective mortality benefit of recreational exercise in longitu-
dinal population studies (25).
Steady-state hemodynamics. Table 2 shows physical charac-
teristics during 1 yr of training in the sedentary seniors with
those obtained in the Masters athletes and the young controls at
baseline. At baseline, there were no significant differences in
body weight and height among the groups. V
˙
O
2 max
was sig
-
nificantly lower in the sedentary seniors than the Masters
athletes or the young controls. HR was significantly lower in
the Masters athletes than the sedentary seniors and the young
controls. Peak HR was significantly lower in both senior
groups than the young controls. SBP and DBP were signifi-
cantly higher, CO was lower, and therefore TPR was signifi-
cantly higher in the sedentary seniors than the Masters athletes
and the young controls. SV was significantly lower in the
sedentary seniors than the Masters athletes and the young
controls.
During 1 yr of training for the sedentary seniors, body
weight decreased significantly at 9- and 12-mo time periods.
V
˙
O
2 max
increased gradually and achieved statistical signifi
-
cance at 6, 9, and 12 mo; however, it remained significantly
decreased compared with the Masters athletes and the young
controls throughout training. Resting HR and peak HR de-
creased gradually throughout training, and resting HR achieved
statistical significance at 12 mo compared with the young
controls. Respiratory rate remained unchanged throughout
training. SBP and DBP measured by cuff decreased signifi-
cantly at 3 mo; however, more prolonged and intense training
did not lead to greater reduction in BP. SBP gradually in-
creased back toward the baseline level during the last 9 mo,
whereas DBP remained significantly decreased up to 12 mo.
These patterns were similar with BP measured by averaging 6
min of quiet resting beat-by-beat data from finger photo-
plethysmography. CO and SV increased gradually, and TPR
decreased throughout training.
Cardiovascular variability and baroreflex sensitivity. Rep-
resentative frequency domain analyses of changes in RRI and
SBP in a senior subject before and after 1 yr of training are
shown compared with those in a young subject before and after
6 mo of training in Fig. 2. Table 3 summarizes the indexes of
cardiovascular variability and baroreflex sensitivity. These in-
dexes from controlled respiration are correlated to the doses of
exercise with a second-order regression model, as shown in
Fig. 3. Data are shown with those obtained from the Masters
athletes and the young controls at baseline. At baseline, the
indexes of HRV and baroreflex sensitivity were decreased
significantly in the sedentary seniors, whereas these indexes
were maintained in the Masters athletes compared with the
young controls. During 1 yr of training for the sedentary
seniors, the indexes of HRV and BP variability increased
progressively throughout training with increasing monthly
TRIMP, although normalized power in LFRR and HFRR
remained unchanged. In contrast, GainLF and GainHF exhib-
ited a “bell-shaped” curve that had a peak adaptation between
3 and 6 mo, equivalent to a monthly TRIMP of 620–950,
which was approximately equivalent to training at 75%
HR
max
, 95–150 min/wk. However, more prolonged and in
-
tense training did not lead to greater improvement for barore-
flex gain. Estimated coherence between SBP and RRI both in
Table 2. Body weight, maximal oxygen uptake, and hemodynamics during quiet, supine rest
Sedentary Seniors
Masters
Athletes
Young
ControlsBaseline 3 mo 6 mo 9 mo 12 mo
Body wt, kg 74.210.5 73.510.6 72.810.3 72.211.3* 70.810.2* 64.613.5 70.510.9
V
˙
O
2max
,ml kg
1
min
1
22.43.6
†‡
23.53.1
†‡
24.54.3*
†‡
25.84.9*
†‡
26.74.4*
†‡
38.35.9 39.44.7
HR, beats/min 639
638
6212
628
5910
535
667
Peak HR, beats/min 16213
16013
16013
15812
15913
16110
19510
Respiratory rate, breaths/min 13.65.0 14.04.2 14.43.9 14.13.5 13.63.6 12.83.1 11.92.7
SBP, mmHg 14011
†‡
1238* 12812*
12712*
13722
†‡
12420 11510
DBP, mmHg 797
†‡
705* 705* 69 4* 734* 6811 677
Stroke volume, ml 75.220.1
†‡
84.020.6 85.122.0 85.016.9 93.417.7* 96.320.8 96.518.2
Cardiac output, 1/min 5.00.6
5.40.8
5.40.8
5.60.8 5.50.6 5.61.1
6.41.0
TPR, dyn s cm
5
1,612255
†‡
1,334209*
1,360284*
1,284218*
1,387170*
1,280259
1,051179
Values are means SD; n 10 for sedentary seniors, 12 for Masters athletes, and 11 for young controls. V
˙
O
2max
, maximal oxygen uptake; SBP, systolic
blood pressure; DBP, diastolic blood pressure; TPR, total peripheral resistance. P 0.05 compared with *baseline,
young controls, and Masters athletes.
1044 AGE, EXERCISE, AND HEART RATE VARIABILITY
J Appl Physiol VOL 99 SEPTEMBER 2005 www.jap.org
LF and HF was near or above 0.5 with a negative phase at
baseline and during training; neither coherence nor phase
changed during training, confirming the validity of using this
technique for the assessment of transfer function gain and
phase (37). Most importantly, SDRR, LFRR, and HFRR in the
sedentary seniors were not appreciably increased during the
first 6 mo of training; however, all of those indexes increased
up to similar levels as the young controls after 12 mo of
training. On the other hand, GainLF and GainHF in the
sedentary seniors remained decreased throughout training com-
pared with those in the young controls, regardless of training
intensity.
Effects of age on trainability. Figure 4 shows the adaptation
of RRI, indexes of cardiovascular variability, and baroreflex
sensitivity after moderate and heavy identical training loads in
the sedentary seniors and the young controls, with P values by
two-way repeated-measures ANOVA. As expected, the age
effects were significant in all of the indexes of HRV and
baroreflex sensitivity. On the other hand, there were no signif-
icant interaction effects in any variable, indicating that the
trainability for cardiac autonomic function after the identical
training loads was similar between the groups. There were no
age, training, or interaction effects in LFBP and HFBP. All of
the indexes of HRV and baroreflex sensitivity were signifi-
cantly lower in the sedentary seniors than the young controls
throughout training, except for LFRR and HFRR after heavy
training, at which point there were no significant differences
between the groups.
DISCUSSION
The major findings from the present study are 1) autonomic
modulation of the heart in sedentary seniors improves with
increasing dose of exercise over 1 yr of training; 2) resting BP
and indexes of baroreflex sensitivity in seniors show a peak
adaptation after relatively light doses of training for 3– 6 mo;
however, higher doses of training do not lead to greater
enhancement of this effect; 3) a heavy dose of training for 12
mo reestablishes most of the age-related deterioration in in-
dexes of HRV to youthful levels, but it does not restore the
age-related decrease in baroreflex sensitivity; and 4) seniors
retain a similar degree of trainability for indexes of HRV and
baroreflex sensitivity compared with young individuals to
identical training loads.
HRV. All of the indexes of HRV were significantly attenu-
ated in the sedentary seniors compared with the young controls
at baseline in the present study, as reported in previous cross-
sectional studies (7, 10, 11, 27, 41). Spectral analysis of HRV
quantifies the dynamic, frequency-dependent changes in HR,
which reflects autonomic modulation of sinus node activity (1,
30). HF power of RRI variability (0.15 Hz) appears to be
modulated predominantly by respiration-induced changes in
vagal activity, whereas LF power of RRI variability (0.15
Hz) is modulated by both vagal and sympathetic activity (1,
30). The prominent decrease in HFRR and LFRR in the
sedentary seniors indicates attenuated autonomic modulation
of sinus node activity, mainly because of decreased vagal
activity with aging (16, 40, 44). For example, parasympathetic
blockade with atropine in humans increases the HR substan-
tially less in elderly than younger subjects (44), suggesting that
the HR at rest is under less parasympathetic control with aging.
However, an alternative interpretation is that decreases in sinus
node function with age make it less sensitive to alterations in
vagal or sympathetic neural activity, which could be normal,
but still have a more limited ability to modulate phase IV
depolarization at the sinus node.
Table 3. Cardiovascular variability
Sedentary Seniors
Masters
Athletes
Young
ControlsBaseline 3 mo 6 mo 9 mo 12 mo
Spontaneous respiration
SDRR, ms 3111
†‡
3210
4029 4025 4929* 5129 4817
LFRR, ms
2
326377 229232
565962 8411,298 1,2802,612 1,1051,496 756625
HFRR, ms
2
88107
111110
240359 297404 422744 8911,697 763774
NormLFRR 0.260.16 0.190.12 0.200.08 0.280.15 0.260.19 0.240.18 0.260.13
NormHFRR 0.080.04
†‡
0.110.09
0.110.06
0.140.08 0.100.05
0.200.16 0.250.19
LFBP, mmHg
2
6.64.7 7.27.9 7.46.3 5.85.7 12.611.5*
4.97.9 3.62.8
HFBP, mmHg
2
1.20.7 1.41.5 2.43.1 1.71.6 1.50.9 1.01.2 1.81.0
GainLF, ms/mmHg 5.23.3
†‡
6.04.5
7.15.9 8.26.7 7.96.1 10.36.2 11.84.9
GainHF, ms/mmHg 6.43.6
†‡
8.87.7 10.613.0 10.59.5 9.66.4 20.320.0 15.17.3
Controlled respiration
SDRR, ms 2813
†‡
3419
3726
4336 4939* 4723 6130
LFRR, ms
2
12494
297576 287385 396654 7751,757 6191,003 747689
HFRR, ms
2
207396
378638
6501,068 1,3362,802 1,3782,748 2,0824,707 2,7203,675
NormLFRR 0.170.11 0.150.08 0.170.09 0.150.10 0.160.09 0.160.11 0.190.14
NormHFRR 0.200.15
0.210.10
0.300.14 0.270.20
0.280.15
0.240.16
0.450.24
LFBP, mmHg
2
3.41.9 5.54.7 4.52.8 10.823.7 15.327.2 3.86.6 2.71.7
HFBP, mmHg
2
4.02.4 3.32.0 4.02.6 5.15.2 6.88.3 4.03.9 6.25.4
GainLF, ms/mmHg 4.62.2
†‡
5.54.3
6.75.2
5.53.6
5.33.9
9.77.7 12.36.4
GainHF, ms/mmHg 5.43.1
6.45.1
8.37.8
6.64.1
6.64.4
12.512.9 16.09.1
Values are means SD; n 10 for sedentary seniors, 12 for Masters athletes, and 11 for young controls. SDRR, standard deviation of R-wave-R-wave
intervals (RRI); LFRR and HFRR, power in low and high frequency of RRI, respectively; NormLFRR and NormHFRR, normalized power in low and high
frequency of RRI, respectively; LFBP and HFBP, power in low and high frequency of SBP, respectively; GainLF and GainHF, low and high frequency transfer
function gain between SBP and RRI, respectively. P 0.05 compared with *baseline,
young controls, and Masters athletes.
1045AGE, EXERCISE, AND HEART RATE VARIABILITY
J Appl Physiol VOL 99 SEPTEMBER 2005 www.jap.org
Arguing against an intrinsic defect in sinus node responsive-
ness with aging alone (10) is the fact that HRV in the Masters
athletes was well maintained compared with the young controls
in the present study, as well as previous cross-sectional studies
(11, 13), suggesting that regular physical activity can prevent
the age-related abnormalities of cardiac autonomic function.
Conversely, longitudinal studies that investigated the effects of
aerobic training on HRV in healthy but initially sedentary
elderly subjects have provided inconclusive results: some stud-
ies reported increased HRV after training (27, 33, 38, 39, 43),
whereas others did not (9, 49). One potential reason for this
discrepancy may be differences in exercise loads performed by
subjects in the previous studies.
In the present study, we found that the indexes of HRV in
the sedentary seniors improved with increasing dose of exer-
cise throughout the year of training. More importantly, these
indexes were not appreciably increased after light-moderate
doses of training after 3– 6 mo, equivalent to a monthly TRIMP
of 620 –950, 75% HR
max
, 95–150 min/wk, but required
heavier doses of training over 12 mo, equivalent to a monthly
TRIMP of 1,300, 75% HR
max
, 200 min/wk, to achieve a
significant effect. Previous longitudinal studies that reported an
increase in indexes of HRV after training in healthy sedentary
elderly subjects used relatively higher doses of exercise (27,
33, 38, 39, 43). For example, Levy et al. (27) showed in elderly
men (age, 60 to 82 yr) that SDRR measured during 2-min
supine rest increased after 6-mo high-intensity training at
50 85% HR reserve for 180 –225 min/wk. In contrast, other
studies using relatively lower doses of exercise failed to show
an increase in indexes of HRV in a similar population (9, 49).
Boutcher and Stein (9) reported in middle-aged men (mean
age, 46 yr) that time domain parameters of HRV measured
during 15-min supine rest remained unchanged after 8-wk
light-intensity training, 60% HR reserve, 60 –90 min/wk.
More recently, Uusitalo et al. (49) also failed to show an
increase in frequency-domain parameters of HRV measured
during 5-min supine rest after 5-yr of low-intensity training,
40 60% V
˙
O
2 max
, 30 60 min/day, 3–5 days/wk, in middle-
aged and older men (age, 53–63 yr). Taken together, these data
suggest that indexes of HRV in healthy elderly subjects are
beneficially modulated only when training is performed vigor-
ously enough, i.e., heavy doses of training equivalent to exer-
cise at 75% HR
max
for 200 min/wk for at least 6–12 mo.
One previous study by Levy et al. (27) reported effects of
similar aerobic training on HRV in healthy young and elderly
subjects. They suggested that an increase in SDRR after 6 mo
of aerobic training occurred in both age groups. In the present
study, we confirmed and extended this observation by carefully
Fig. 3. Dose-response relationship of dynamic cardiovascular indexes to
exercise intensity and volume of training (monthly TRIMP) in sedentary
seniors (n 10, F). Data are shown with values obtained from Masters athletes
(n 12, E) and young controls (n 11, ) at baseline. Means and SE bars are
presented. A: standard deviation of RRI (SDRR). B: power in high frequency
of blood pressure (HFBP). C and D: power in low (LFRR) and high frequency
of RRI (HFRR), respectively. E and F: low- (GainLF) and high-frequency
transfer function gain (GainHF), respectively. P 0.05 compared with
*pretraining baseline, †young controls, and ‡Masters athletes.
Fig. 4. RRI and indexes of cardiovascular variability at baseline and after
moderate and heavy doses of training in sedentary seniors (n 10, F) and
young controls (n 11, ) with P values of the effects of age, training (Tr),
and the interaction of age training (Int) by two-way repeated-measures
ANOVA. BL, baseline; moderate, moderate volume of training (6 mo for
sedentary seniors, 3 mo for young controls); heavy, heavy volume of training
(12 mo for sedentary seniors, 6 mo for young controls). A: RRI. B: SDRRI. C
and D: power in LFRR and HFRR, respectively. E and F: GainLF and Gain
HF, respectively. P 0.05 compared with *pretraining baseline within group,
†young controls at the same points, and §young controls at baseline.
1046 AGE, EXERCISE, AND HEART RATE VARIABILITY
J Appl Physiol VOL 99 SEPTEMBER 2005 www.jap.org
controlling the exercise stimulus in young and older groups of
subjects. We showed that there were no significant interaction
effects of age and training in any index of HRV and baroreflex
sensitivity as well as RRI in the sedentary seniors and the
young controls, after identical moderate and heavy loads of
training. From these observations, we conclude that senior
subjects retain a similar degree of trainability of cardiac auto-
nomic function in response to dynamic exercise as young
subjects.
Baroreflex sensitivity and BP variability. Transfer function
analysis of spontaneous variations between BP and RRI has
been employed for the evaluation of dynamic properties of
baroreflex function in humans (22, 23, 50). The assessment of
baroreflex function in this analysis reflects a closed-loop rela-
tionship between BP and RRI with the basic premise that
oscillations in BP lead to baroreflex-mediated oscillations in
RRI (14). In contrast, a mathematical simulation of cardiovas-
cular control showed that the feed-forward effects of HR on BP
may be more complicated than simple buffering via the barore-
flex (6). For example, Taylor and Eckberg (45) showed that
oscillations in BP were reduced when the RRI was fixed via
cardiac pacing in humans in the supine position and suggested
that respiratory sinus arrhythmia can contribute to arterial
pressure oscillations. However, Zhang et al. (50) recently
reported that, after ganglion blockade, BP variability at high
frequencies remained unchanged even though R-R variability
was virtually abolished under supine resting conditions. This
result provides evidence that BP variability at high-respiratory
frequencies is mediated to a large extent by mechanical effects
of respiration on intrathoracic pressure and/or cardiac filling
and is less influenced by feed-forward effects of changes in
RRI on BP variability. In addition, the phase was always
negative, both in HF and LF in all groups, and did not change
during training in the present study. Finally, transfer function
gain correlates significantly with other measures of baroreflex
function, including vasoactive drug methods and sequence
analysis (31, 35, 36). Therefore, the premise of this study is
that the possibility of feed-forward effects of RRI on BP are
minimal under the specific conditions of the study and that the
technique of transfer function analysis provides a reasonable
index of dynamic baroreflex function.
In contrast to the prominent plasticity of HRV, baroreflex
sensitivity of the sedentary seniors after training remained
considerably lower than that of the young controls at baseline,
even at the peak response to training. In addition, contrary to
the results of the indexes of HRV, baroreflex sensitivity of the
sedentary seniors showed a peak adaptation after more mod-
erate doses of training; more prolonged and intense exercise
did not lead to greater enhancement of these changes. These
observations appear inconsistent with previous observations
from cross-sectional studies that baroreflex sensitivity by the
cross-spectral method is decreased along with HRV in seden-
tary elderly subjects but that both indexes are maintained in
physically fit elderly individuals (11, 13, 21). Similarly, in the
present study, baroreflex sensitivity in the Masters athletes was
preserved along with HRV compared with the young controls.
One potential explanation for this inconsistency between
cross-sectional and longitudinal studies may be the effect of
circulatory mechanics on cardiovascular variability. Changes
in cardiac compliance influence the change in left ventricular
filling from the respiratory shift in thoracic blood volume and
thereby modulate beat-to-beat SV and BP, influencing the
amount of baroreceptor distortion during a pressure pulse (26).
Recently, our laboratory demonstrated that lifelong endurance
training preserves ventricular compliance, which is decreased
prominently with sedentary aging in these same subjects (3).
This increased ventricular compliance may augment respira-
tory fluctuation in SV and thereby BP in lifelong fit compared
with unfit individuals.
The fact that BP variability at the respiratory frequency, i.e.,
HFBP, increased after 9 –12 mo of training in the present study
suggests that ventricular compliance, or at least respiratory
modulation of SV, may well have increased during training in
the sedentary seniors. Such increased BP variability should
increase the signal to arterial baroreceptors; however, GainHF
was not correspondingly enhanced after 9 –12 mo of training.
This discrepancy suggests that, although cardiac mechanics
may have been improved, other components of baroreflex
sensitivity (21, 29), i.e., most likely the mechanical transduc-
tion of pressure by the baroreceptors, or sensitivity of the
baroreceptor-HR reflex arc, remain unchanged, despite 12 mo
of training in the sedentary seniors. It has been suggested that
the age-related decrease in cardiovagal baroreflex sensitivity is
caused mostly by an attenuated mechanical transduction of
pressure into baroreceptors due to decreased arterial compli-
ance (29). Conversely, preserved baroreflex sensitivity in fit
elderly subjects is associated with a preserved mechanical
transduction by an improved arterial compliance (21, 29), as
well as a preserved neural transduction (21). It may be that
more prolonged training, possibly supplemented by other ther-
apies designed to improve arterial stiffness, is necessary to
improve baroreflex sensitivity in chronically sedentary seniors.
Clinical implications. A critical question regarding the ef-
fects of exercise on cardiovascular morbidity and mortality is
the intensity and duration of exercise training required to
achieve a clinically meaningful reduction in cardiovascular risk
(19, 22, 25, 34). Decreases in vagal activity, manifested by
decreased indexes of HRV and baroreflex sensitivity, known to
become manifest with aging (7, 10, 11, 27, 41), may reflect a
decrease in fibrillation threshold and predispose to ventricular
fibrillation (20). Epidemiological studies have shown an in-
verse association between indexes of HRV or baroreflex sen-
sitivity and an increased incidence of cardiac events and
mortality in clinically disease-free individuals, even after ad-
justing for other known risk factors (15, 48). In contrast, it has
been suggested that increases in cardiac parasympathetic ac-
tivity with aerobic training may exert a protective effect against
life-threatening arrhythmias (8, 20). Therefore, the increased
HRV parameters after heavy doses of training for 12 mo in the
sedentary seniors may reduce the risk of ventricular fibrillation
and may be a key mechanism for the reduction in cardiovas-
cular risk associated with exercise training in this population.
Limitations. Because training increased in dose over the
entire study, and there was no control group that did not
exercise, we cannot differentiate clearly the effects of time or
duration of training per se from the specific doses of training.
In addition, because the periods of training to achieve the
similar doses of training in the sedentary seniors were twice as
long as those in the young controls, we cannot exclude the
possibility that the difference in the duration of training be-
tween the two groups might affect the results. Hence, our
results must be interpreted cautiously. However, we suspect
1047AGE, EXERCISE, AND HEART RATE VARIABILITY
J Appl Physiol VOL 99 SEPTEMBER 2005 www.jap.org
that continued training over time at any given dose is not likely
to change cardiovascular parameters such as those measured
here. In addition, these measures of HR and BP variability
appear robust and change little over time periods as long as 1
yr without any intervention (23, 39, 43). Moreover, our labo-
ratory previously demonstrated that the cardiovascular adapta-
tion to the same dose of endurance training was comparable
between subjects in their late twenties and in their fifties in the
same subjects in a long-term longitudinal study, even though
the dose of training was achieved over a 6-mo interval later in
life compared with 8 wk at a younger age (28).
The subjects examined in the present study were elderly but
free from known cardiovascular disease. Thus the present
results are more relevant to primary rather than secondary
coronary heart disease prevention. Because the presence of
cardiovascular disease decreases HRV, regardless of aging (2,
7), the results of this study could be different in patients with
manifest cardiovascular disease. It is possible that such patients
could have a greater range of responsiveness and thus have a
more robust or sustained response to training. Indeed, the
effects of aerobic training on HRV and baroreflex sensitivity in
chronic heart failure or myocardial infarction patients suggest
a considerable and significant improvement in these parameters
(12, 42).
In conclusion, indexes of HRV in sedentary seniors improve
with increasing dose of exercise over 1 yr of training, with
heavy doses of training for 12 mo, equivalent to exercise at
75% HR
max
for 200 min/wk, restoring most of the age-
related deterioration in these indexes. Conversely, lower doses
of training for 3–6 mo, equivalent to exercise at 75% HR
max
for 95–150 min/wk, achieve a modest hypotensive effect and
may improve indexes of baroreflex sensitivity. However,
higher doses of training do not lead to greater enhancement of
these changes, and the age-related decrease in baroreflex sen-
sitivity is not restored to youthful levels even after 12 mo of
heavy training. Finally, healthy sedentary seniors retain a
similar but not greater degree of trainability to dynamic exer-
cise as healthy young individuals for autonomic control of the
circulation.
ACKNOWLEDGMENTS
The authors express appreciation to the subjects for willing participation in
the project. The authors thank Kimberly Williams and Marta Newby at the
Institute for Exercise and Environmental Medicine, Dallas, TX, for help with
the data collection.
GRANTS
This study was supported by National Institute on Aging Grant AG-17479 02.
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1049AGE, EXERCISE, AND HEART RATE VARIABILITY
J Appl Physiol VOL 99 SEPTEMBER 2005 www.jap.org
    • "Orthostatic hypotension is a common symptom in PD and a reduced baroreflex response plays a role in its pathophysiology [107]. Endurance exercise training has been associated with improvement of the baroreflex function in healthy seniors [108] . Although the benefits of endurance exercise training on autonomic cardiovascular adaptations have been well demonstrated in various populations, no study has examined this relation in PD. "
    [Show abstract] [Hide abstract] ABSTRACT: Background: Despite the benefits of medications and surgical interventions for Parkinson's disease (PD), these treatments are not without complications and neuroprotective strategies are still lacking. Therefore, there is a need for effective alternative approaches to treat motor and non-motor symptoms in PD. During the last decade, several studies have investigated endurance exercise training as a potential treatment for individuals with PD. Objective: This paper reviews the therapeutically beneficial effects of endurance exercise training on motor and non-motor symptoms in PD. Methods: First, we performed a systematic review of the literature on the effects of endurance exercise training on motor and non-motor signs of parkinsonism, functional outcomes including gait, balance and mobility, depression and fatigue, quality of life and perceived patient improvement, cardiorespiratory function, neurophysiological measures, and motor control measures in PD. Second we performed a meta-analysis on the motor section of the UPDRS. Then, we focused on several important factors to consider when prescribing endurance exercise training in PD such as intensity, duration, frequency, specificity and type of exercise. In addition, we identified current knowledge gaps regarding endurance exercise training in PD and made suggestions for future research. Results: A total of eight randomized controlled trials met the inclusion criteria and were reviewed. This systematic review synthesizes evidence that endurance exercise training at a sufficiently high level enhances cardiorespiratory capacity and endurance by improving VO2 max and gait in moderately to mildly affected individuals with PD. However, there is not yet a proven effect of endurance exercise training on specific features of PD such as motor signs of parkinsonism. Conclusion: Endurance exercise training improves physical conditioning in PD patients; however, to date, there is insufficient evidence to include endurance exercise training as a specific treatment for PD. There is a need for well-designed large-scale randomized controlled trials to confirm benefits and safety of endurance exercise training in PD and to explore potential benefits on the motor and non-motor signs of PD.
    Full-text · Article · Nov 2014
    • "In all cases, at least three of these criteria were achieved, confirming the identification of VO 2max per the ACSM guidelines [30]. During exercise testing, arterial pressure (Tango+, Suntech), electrocardiogram (Mortara, Mortara Instrument), cardiac output (C2H2 rebreathing method) and ventilation were measuredcontinuously to monitor cardiopulmonary responses.Of note, our previous studies have demonstrated that by using these methods, VO 2max can be measured reliably in sedentary elderly subjects [31, 32]. "
    [Show abstract] [Hide abstract] ABSTRACT: Background: With age, performance of motor tasks becomes more reliant on cognitive resources to compensate for the structural and functional declines in the motor control regions in the brain. We hypothesized that participants with amnestic mild cognitive impairment (aMCI) are more prone to motor dysfunctions than cognitively normal older adults under dual-task conditions where competitive demands challenge cognitive functions while performing a motor task simultaneously. Methods: Sixteen aMCI participants (females=9, age=64±5yrs, clinical dementia rating score=0.5) and 10 age- and education-matched cognitively normal adults (females=5, age=62±6yrs) participated. Using a 10-meter-walk test (10MW), gait velocity was recorded at baseline and under 4 different dual-task (DT) conditions designed to challenge working memory, executive function, and episodic memory. Specifically, DT1: verbal fluency; DT2: 5-digit backward span; DT3: serial-7 subtraction; and DT4: 3-item delayed recall. Physical function was measured by Timed Up-and-Go (TUG), simple reaction time (RT) to a free-falling yardstick, and functional reach (FR). Results: No difference was found in physical functions, aerobic fitness, and exercise cardiopulmonary responses between aMCI participants and controls. However, aMCI participants showed more pronounced gait slowing from baseline when compared to the controls (p<0.05; p=0.001; p<0.001; p<0.001, respectively). Conclusions: Our finding supports the theory of shared resource of motor and cognitive control. Participants with aMCI manifested more gait slowing than cognitively-normal older adults under DT conditions, with the largest differences during tests of working and episodic memory. The outcome of dual-task assessment shows promise as a potential marker for detection of aMCI and early Alzheimer disease.
    Full-text · Article · May 2014
    • "Rackzak et al., [48] reported parasympathetic nervous system (PNS) dominance by measuring HRV and increased BRS after long-term exercise training. Another study reported increased HRV and BRS in Masters Athletes compared with decreased values for sedentary seniors [49]. Several other studies also concluded that regular physical activity increases vagal influence on the HR and BRS, while the sympathetic tone may be decreased50515253545556575859. "
    [Show abstract] [Hide abstract] ABSTRACT: Heart rate variability (HRV) analysis is a popular tool for the assessment of autonomic cardiac control. These measurements are increasingly employed in studies ranging from investigations of central autonomic regulation; to studies exploring the link between psychological processes and physiological functioning; to the indication of ANS activity in response to exercise, training and overtraining. Many publications elaborate on the effect of exercise on HRV and by implication on cardiac functioning. However, results on the effects of exercise on the autonomic control of the heart are often contradictory and incomplete in the normal population and in disease. In order to understand and employ the effects of exercise in patients with cardiovascular disorders it is of primary importance that agreement should be reached on the effects of exercise in the normal and healthy population. In this chapter, a selection of older and more recent publications, investigating autonomic training effects as measured by cardiovascular variability indicators, are summarized. Reasons for heterogeneous results are identified and discussed. The chapter concludes with specific recommendations for future research.
    Full-text · Chapter · Oct 2013 · Current Alzheimer research
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