Hindawi Publishing Corporation
Rehabilitation Research and Practice
Volume 2011, Article ID 761958, 6 pages
TaiChi EnhancestheEffectsof EnduranceTraininginthe
Rehabilitationof ElderlyPatients withChronicHeart Failure
Cardiovascular Research Unit, Department of Medical Sciences, Centre for Clinical and Basic Research, IRCCS San Raffaele,
via della Pisana 235, 00163 Roma, Italy
Correspondence should be addressed to Giuseppe Caminiti, email@example.com
Received 8 June 2010; Revised 29 July 2010; Accepted 27 August 2010
Academic Editor: Richard Crevenna
Copyright © 2011 Giuseppe Caminiti et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
Purpose. To assess if Tai Chi added to endurance training (ET) is more effective than ET alone in improving exercise tolerance
and quality of life (QOL) of elderly patients with chronic heart failure (CHF). Design. Sixty CHF patients, age 73.8 ± 6 years,
M/F 51/9, were enlisted. Thirty pts were randomized to combined training (CT) performing Tai Chi +ET and 30 patients to ET
(ET only). Methods. At baseline and after 12 weeks all patients underwent 6-minute walking test (6MWT), assessment of amino
terminal probrain natriuretic peptide (NT-pro BNP), quadriceps maximal voluntary contraction (MVC) and peak torque (PT),
Results. Distance at 6mwt improved in both groups with significant between-groups differences (P = .031). Systolic BP and
NT-proBNP decreased significant in the CT group compared to ET (P = .025) and P = .015), resp.). CT group had a greater
significant improvement in physical perception (P = .026) and a significant increase of PT compared to ET group. Conclusions.
The association of Tai Chi and ET improves exercise tolerance and QOL of patients with CHF more efficiently than ET.
Chronic heart failure (CHF) is a disease increasingly rec-
ognized as a health burden worldwide. Patients with CHF
exhibit impaired exercise tolerance that limits their exercise
capacity and quality of life. These symptoms are related to
both central and peripheral factors such as structural and
functional abnormalities of skeletal muscle [1–3].
It has been widely demonstrated that endurance training
(ET) improves aerobic capacity of patients with CHF.
Moreover, ET exerts several beneficial effects in CHF patients
by improving skeletal muscle structure and function and
peripheral blood flow; decreasing neurohormonal function
and mortality rate [4–7].
low intensity physical activity derived from a traditional Chi-
nese martial art, as a possible nonpharmacological treatment
of CHF. Tai Chi seems to improve exercise tolerance, and
it could induce favourable hemodynamic changes on CHF
subjects compared to usual care [8–10]. Outcome measures
of these small studies included quality of life (QOL),
exercise capacity, B-type natriuretic peptide, catecholamine
levels, blood pressure (BP), arrhythmogenes, and heart rate
It is not clear if the association of Tai Chi and ET could
exert additive effects when administered to CHF subjects
already undergoing a cardiac rehabilitation program. Until
now no studies have been published on the effects of a
Chi and ET.
The first aim of this study was to assess if CT is more
effective than ET alone in improving exercise tolerance
of elderly patients with CHF. Secondary endpoints were
changes in heart rate, amino terminal probrain natriuretic
peptide (NT-pro BNP), muscle strength, and QOL.
2.1. Study Population and Study Design. We enlisted 60
patients with diagnosed CHF due to left ventricular systolic
2Rehabilitation Research and Practice
dysfunction, mean age 73 ± 6 years, ejection fraction 33
± 9%, and M/F 51/9. All patients were in New York Heart
Association (NYHA) functional class II. The cause of heart
failure was ischaemic heart disease in 48 patients, idiopathic
dilated cardiomyopathy in 12 patients. At the time of their
enlistment all patients were out-hospital patients, attending
to a cardiac rehabilitation program in our day hospital
at IRCCS S. Raffaele Istitute of Rome. Inclusion criteria
were age >65 years, CHF of more than one year duration
due to ischemic or nonischemic dilated cardiomyopathy,
left ventricular ejection fraction (LVEF) ≤45%, NYHA
functional class II, stable clinical conditions and optimal
HF treatment without changes for at least 3 months.
Exclusion criteria were history of myocardial infarction or
angina less than three months, decompensated heart failure,
complex ventricular arrhythmia, angina, and neurological or
orthopaedic conditions limiting the exercise protocol. This
was an open randomized pilot study. After the completion
of baseline testing participants were simply randomized
by lot to either the CT group or the ET group. Thirty
patients received CT treatment (Tai-Chi+ET) 3 times/week;
30 patients received ET treatment 3 times/week. All patients
of the two groups were on top of their medical therapy.
All patients gave informed consent to participate in the
study, which was approved by the local Ethics Committee
and conforms to the principles outlined in the Declaration
of Helsinki and to the GCP guidelines of the European
2.2. Endurance Training. It was performed according to the
AHA guidelines . Every exercise session included 10
exercises, and 30 minutes of aerobic exercise with cycling or
walking at 60%–70% of estimated VO2 max.
2.3. Tai Chi. In general, Tai Chi is a low-impact, weight-
to dissipate force throughout the body while the subject
changes poses, with well-coordinated sequences of both
isometric and isotonic segmental movements in the trunk
and 4 extremities. Every session included 10 minutes of
warm-up exercises, 30 minutes of Tai Chi practice, and 10
minutes of cooldown exercises. The Tai Chi programme
was a modified 10-movement Yang style taught by an
experienced Tai Chi instructor similar in style to the routine
proposed by Wolf . One-to-two movements were taught
each week for 8 weeks. The complete form was practised
for the last 4 weeks of the study. Emphasis was placed on
performing the movements in a slow, relaxed way. Tai Chi
sessions were conducted by an expert Tai Chi trainer with
a trained cardiac rehabilitation therapist also in attendance.
During Tai Chi practice, subjects imitated the motions and
postures of the Tai Chi instructor with the same speed.
In order to balance the total amount of exercise, exercise
sessions were organized as follows: all subjects of both
groups performed 4 sessions /week. Patients of the CT group
performed Tai Chi for 30 minutes two times a week and
cycling or walking for 30 minutes 2 times a week (in different
days). Patients of the ET group performed cycling or walking
for 30 minutes four times a week.
At baseline, in order to estimate their maximal exercise
capacity, all subjects performed a symptoms-limited exercise
test on a treadmill using a standard Bruce Modified protocol.
A resting ECG was performed and repeated at the end of
each stage during exercise and during the recovery phases.
Data on heart rate and blood pressure were collected during
these phases. Maximal oxygen uptake was estimated trough
method of heart rate reserve and the training heart rate was
estimated based on the following formula. Training heart
rate = (maximum HR-resting HR) × desired intensity (%)
+ resting HR.
Changes on exercise tolerance were evaluated by 6MWT.
The test was performed at baseline and at the end of the
was supervised by a physical therapist. Patients were asked
to walk at their own maximal pace a 100m long hospital
corridor. Every minute a standard phrase of encouragement
was told. Patients were allowed to stop if signs or symptoms
of significant distress occurred (dyspnoea, angina) though
they were instructed to resume walking as soon as possi-
ble. Results of 6MWT were expressed in distance walked
(metres). The Borg scale was used to rate perceived exertion
(RPE), and the perceived level of dyspnoea was rated on the
Borg category ratio scale .
During all the training sessions, HR was assessed in each
subject (Polar Team System; Polar Electro Oy), and data were
downloaded on a portable personal computer and analyzed
using a dedicated software (Polar ProTrainer 5; Polar Electro
and at follow-up examination a vertical visual analog scale to
test their quality of life. The visual analog scale was a 10cm
line with a mark at each centimetre. Physical and social QOL
were evaluated by MacNewQLMI , a self-administered
questionnaire previously validated in patients with MI [16,
27 items in three domains (physical, emotional, and social)
with a Global score, has a 2-week duration, and is scored
from 1 (low HRQL) to 7 (high HRQL).
ment: to determine the maximal muscle strength, isometric
dynamometry testing (REV9000, Tecno-Gym) of the quadri-
ceps muscles was performed at baseline, and at the end of the
study. All measurements were performed while the subject
was seated on the device; the chest was fixed by 2 straps,
the pelvis and knees flexed at an angle of 90◦. The ankle of
the tested leg was attached to the strength transducer by a
Velcro strip and the patient then carried out 3 consecutive
time 7s); the highest value was considered as the maximal
strength (MVC, N). The isokinetic muscle strength of the
knee extensors was assessed by the same dynamometric
system, recording the isokinetic strength as torque. Patients
performed 5 consecutive knee extension movements with
Rehabilitation Research and Practice3
Table 1: Baseline Features of the Overall Population and Patients of CT and ET groups.
Overall population CT (N = 30)
ET (N = 30)
Cause of heart failure
Ischemic heart disease
Idiopathic dilated cardiomyopathy
Ejection fraction, %
BMI: body mass index
LVDD: left ventricular diastolic diameter
LVDD: left ventricular systolic diameter.
maximal effort and with an angular speed of 90◦/s; with the
dominant leg the highest value obtained was regarded as the
peak torque (PTmax; Nm).
2.6. NT-pro BNP Assessment. At baseline and at 12 weeks
Venous blood samples were withdrawn from an antecubital
vein into chilled ethylene-diamine-tetraacetic acid Vacu-
tainer test tubes after 20 minutes of rest with patients
in a supine position. Samples were placed immediately
on ice-cold water, and the tubes were then centrifuged
at 4000r.p.m. at 4◦C for 15 minutes. NT-pro BNP was
determined by a commercially available electrochemilumi-
nescence immunoassay based on a polyclonal antibody-
based sandwich chemiluminescence assay (Roche Diagnos-
tics, Germany) using an autoanalyser (Elecsys 2010)
2.7. Statistical Analysis. Differences in baseline character-
istics between CT and ET groups were evaluated by the
chi-square and unpaired t test. Within-group changes in
the reported variables were evaluated by the paired t-test
or Wilcoxon signed rank test for nonnormally distributed
variables. Between groups comparisons were performed by
the unpaired t-test and Mann-Whitney rank sum test. The
primary and secondary outcomes were evaluated comparing
the delta (baseline—12 weeks) of CT versus ET using the
tailed P value of <.05 was considered significant. All analyses
were performed with a commercially available statistical
package (SPSS for Windows version 12.0, Chicago, Illinois).
Clinical characteristics of the study patients are reported
in Table 1. At baseline no differences on anthropomet-
ric, clinical, or echocardiographic parameters between the
two groups examined were noted. Most of the patients
were receiving beta-blockers (88%), angiotensin-converting
enzyme inhibitors or angiotensin receptor antagonists
(96%), or aldosterone receptor blockers (63%); 58% were
taking diuretics, and 36% were receiving digitalis. Medica-
tions were not altered throughout the study.
Patients of CT group trained at a variable intensity
(during endurance training: at 66 ±5% VO2; during Tai Chi
practice at 52 ± 3% VO2). Conversely patients of ET group
had a constant intensity of training (at 67 ±4% VO2).
3.1. Exercise Tolerance and Hemodynamic Profile. After 12-
weeksof treatment,NYHAfunctionalclassimproved in 36%
of CT and 32% of ET without between-groups differences.
Distance walked at 6MWT increased (from 214 ± 32m to
291±46m; P = .0001) in the CT group and in the ET group
4Rehabilitation Research and Practice
Table 2: Comparison of Delta (Baseline versus 12 Weeks) of Hemodynamic, and Muscle Strength in the CT and ET Groups. Data Are
Expressed as Mean ± Standard Deviation.
CT group (n = 30)
ET group (n = 30)
(P) BaselineDelta BaselineDelta
Heart rate, bpm
Systolic BP, mmHg
Diastolic BP, mmHg
NT pro-BNP, pg/mL 136.4 ±31
214.9 ±32 291.5 ±46 77.4 ±26 219.2 ±23272.0 ±33 53.2 ±16.031
72.3 ± 12
84.3 ± 14
65.4 ± 15
6MWT: 6 minutes walking test
BP: blood pressure
NT pro-BNP: amino terminal probrain natriuretic peptide
MVC: maximal voluntary contraction
PT: peak torque.
(from 219 ± 23m to 272 ± 33m; P = .0001) with significant
between-groups difference (P = .031) (Table 2). The Borg
scale decreased in both group (CT −2.1 ± 0.3; ET 1.9 ± 0.4;
resp.) without significant between-groups differences (P =
Rest HR decreased by 11.2% beats/min in the CT group
and by 6.8% beats/min in the ET group (between groups
P = .074). Systolic BP decreased by 12.3% in the CT group
differences(P = .025).DiastolicBPdecreasedinbothgroups
at a similar degree. NT-proBNP levels decreased in both
groups (CT = −28%; ET = −18%) with significant between-
groups differences (P = .015).
PT of the quadriceps had a higher significant increase in
the CT group compared to ET (P = .037) (Table 2). There
was a trend toward a greater increase of MVC in the CT
groups compared to ET (P = .069).
3.2. Quality of Life. After 12-weeks, the overall assessment of
QOL by a visual analog scale showed a similar improvement
to 6.4 ± 0.8); (ET: from 4.3 ± 0.7 to 6.2 ± 0.9) without
significant between-groups differences (P = .137). Physical
QOL evaluated by MacNewQLMI improved in patients in
the CT group to a greater extent than ET group (+32.3%
versus +23%, between groups P = .026). Patients of the CT
group had a trend to a greater improvement on social (+12%
versus +5%; P = .058) and emotional (+9% versus +6%;
P = .083) QOL than ET group.
3.3. Clinical Outcome. Tai Chi and ET were both well
tolerated. No patients had adverse events during the exercise
protocol. No patient died during the follow-up period.
Worsening HF occurred in 1 patient of the ET group and was
managed only by increasing the dose of furosemide. None
patient required hospital stay during the study period. Three
patients (10%) of the ET group withdraw from the study.
The present pilot study shows two original results. First, we
demonstrated that a CT including Tai Chi and ET improves
exercise tolerance and quality of life of elderly patients with
CHF to a greater extent than ET alone. Second, our data
suggest that CT could lead to a better hemodynamic profile
compared to ET alone.
in the CT group. This improvement of exercise capacity
ing only ET (24% increase) and appears considerably better
than those reported by other studies where the increase of
functional capacity after Tai Chi was ranging from 7% to
26% [8–10]. However, some significant differences between
ours and other studies should be underlined. At first we
enlisted only patients in stable clinical conditions at early-
intermediate stage of the disease (only NYHA class II). Con-
ber of patients enrolled were in the NYHA class III. More-
over, for the first time we evaluated the combined effects of
ET associated to Tai Chi on exercise capacity. In fact previous
authors have suggested Tai chi only as a safe alternative
to conventional low intensity exercise training, particularly
for subjects with CHF who are not suitable for ET because
they are elderly or in very advanced stage of the disease.
Conversely, our results suggest a new role for Tai Chi in the
who are contemporaneously performing ET. The mecha-
nisms by which CT enhances the effects of ET are unclear.
Our data suggest that they could be related to a combination
of physicaland psychologicalfactors.Among physicalfactors
we would distinguish central and peripheral variables.
Rehabilitation Research and Practice5
4.1. Central Variables. In our study a 12-weeks CT lead to
a significant 12.3% reduction of systolic BP compared to
6.4% of ET alone. Our data confirm previous observations:
a reduction of mean blood pressure has been found for
regular Tai Chi practice in several studies. A recent review of
twenty-six studies showed that twenty-two of them reported
reductions in BP with tai chi (3–32mmHg systolic and 2–
18mmHg diastolic BP reductions ). Tai Chi seem to
have similar effects ET on systolic BP. Young et al. 
found changes in systolic BP, after 12 week of −8.4mmHg
and −7.0mmHg in the aerobic exercise and Tai Chi groups,
respectively. The effects of CT on HR and BP could be the
result of a stronger modulation of neurohormonal activity
in the CT group activity as demonstrated by other authors
. We observed a significant reduction of NT-proBNP
levels in the CT group compared to ET. A similar reduction
of natriuretic peptide was registered by Yeh et al.  who
compared Tai Chi versus usual care in patients with CHF.
We speculate that the reduction of NT-proBNP levels could
be related to an improvement of cardiac filling pressure in
subjects performing CT to a greater extent than ET.
4.2. Peripheral Variables. We observed a significant increase
of isokinetic strength of quadriceps in the CT group com-
a greater increase in the CT group than ET. Objective mor-
phological and functional abnormalities, relatively indepen-
dent of reduced blood flow, are present in the muscle of CHF
patients . These maladaptive changes in the muscles,
are involved in symptoms development. Moreover, low mus-
cle strength is related to poor outcome in CHF patients .
Exercise training is effective in improving muscle strength in
elderly people  and patients with heart failure . Sig-
nificant improvement in muscle strength in knee and ankle
flexors and extensors have been demonstrated in elderly
healthypeople afterTaiChi [28,29] while,toourknowledge,
no studies have evaluated the effects of Tai Chi on muscle
strength in patients with CHF. Our data suggest that Tai Chi
could enhance the effects of ET also in peripheral factors.
According to our data CT training seems to be superior
to ET alone also in the psychological and motivational
field. In our study patients allocated to CT group had a
significant increase of physical perception compared to ET.
Our data are in line with other studies who evaluated the
effects of Tai Chi on psychological responses in subjects
with cardiovascular diseases [30–32]. In these studies Tai Chi
have shown improvement compared with the control group
in several indices of psychological well-being targets such
as depression, psychological distress, positive well-being,
life satisfaction, and perceptions of health. In the recent
randomized pilot study of Barrow et al.  on patients
with symptomatic CHF, a 16-week Tai Chi program leads to
a significant improvement of depression scale compared to
4.3. Study Limitations. Our study included only 9 (15%)
female patients and we can not generalize our results to
and our data should be confirmed in further well-powered
studies. Despite our data on blood pressure and HR suggest
directly measure the neurohormonal activity in our patients.
In conclusion, our study suggests that the association
of Tai Chi to ET can improve exercise tolerance of patients
with CHF to a greater extent than ET alone. Moreover, CT
seems to determine better hemodynamic and psychological
effects than ET. CT could play an important role in the
rehabilitation of patients with chronic heart failure in stable
Results of this pilot study are promising, considering its
short duration and the large magnitude of improvement in
cardiovascular fitness observed.
The authors confirm that all authors have contributed to this
paper and the final version of this paper has been accepted
by all of them. They do not have any financial interest to
 A. L. Clark, “Origin of symptoms in chronic heart failure,”
Heart, vol. 92, no. 1, pp. 12–16, 2006.
 A. J. S. Coats, “The ’Muscle Hypothesis’ of chronic heart
failure,” Journal of Molecular and Cellular Cardiology, vol. 28,
no. 11, pp. 2255–2262, 1996.
 H. Drexler, U. Riede, T. Munzel, H. Konig, E. Funke, and H.
Just, “Alterations of skeletal muscle in chronic heart failure,”
Circulation, vol. 85, no. 5, pp. 1751–1759, 1992.
 R. Hambrecht, J. Neibauer, E. Fiehn et al., “Physical training
in patients with stable chronic heart failure: effects on
cardiorespiratory fitness and ultrastructural abnormalities of
leg muscles,” Journal of the American College of Cardiology, vol.
25, no. 6, pp. 1239–1249, 1995.
 R. Belardinelli, D. Georgiou, G. Cianci, and A. Purcaro,
“Randomized, controlled trial of long-term moderate exercise
quality of life, and clinical outcome,” Circulation, vol. 99, no.
9, pp. 1173–1182, 1999.
 K. A. Volaklis and S. P. Tokmakidis, “Resistance exercise
training in patients with heart failure,” Sports Medicine, vol.
35, no. 12, pp. 1085–1103, 2005.
 M. F. Piepoli, “Exercise training meta-analysis of trials in
patients with chronic heart failure (ExTraMATCH),” British
Medical Journal, vol. 328, no. 7433, pp. 189–192, 2004.
 G. Y. Yeh, M. J. Wood, B. H. Lorell et al., “Effects of Tai
Chi mind-body movement therapy on functional status and
exercise capacity in patients with chronic heart failure: a
randomized controlled trial,” American Journal of Medicine,
vol. 117, no. 8, pp. 541–548, 2004.
 G. Yeh, P. Wayne, and R. Phillips, “T’ai Chi exercise in patients
with chronic heartfailure,” Medicineand SportScience,vol. 52,
pp. 195–208, 2008.
 D. E. Barrow, A. Bedford, G. Ives, L. O’Toole, and K. S.
Channer, “An evaluation of the effects of Tai Chi Chuan and
Chi Kung training in patients with symptomatic heart failure:
a randomised controlled pilot study,” Postgraduate Medical
Journal, vol. 83, no. 985, pp. 717–721, 2007.
6 Rehabilitation Research and Practice Download full-text
 G. J. Balady, P. A. Ades, P. Comoss et al., “Core components of
ment for healthcare professionals from the American Heart
Association and the American Association of Cardiovascular
and Pulmonary Rehabilitation,” Circulation, vol. 102, no. 9,
pp. 1069–1073, 2000.
 S. L. Wolf, C. Coogler, and T. Xu, “Exploring the basis for
Tai Chi Chuan as a therapeutic exercise approach,” Archives
of Physical Medicine and Rehabilitation, vol. 78, no. 8, pp. 886–
 R. O. Crapo, R. Casaburi, A. L. Coates et al., “ATS statement:
guidelines for the six-minute walk test,” American Journal of
 G. Borg, G. Borg’s Perceived Exertion and Pain Scales, Human
Kinetics, Champaign, Ill, USA, 1998.
 N. Oldridge, G. Guyatt, N. Jones et al., “Effects on quality of
life with comprehensive rehabilitation after acute myocardial
infarction,” American Journal of Cardiology, vol. 67, no. 13, pp.
 T. R. McConnell, C. A. Laubach Jr., M. Memon, J. K. Gardner,
T. A. Klinger, and R. J. Palm, “Quality of life and self efficacy
acute myocardial infarction and bypass revascularization
surgery,” American Journal of Geriatric Cardiology, vol. 9, no.
4, pp. 210–218, 2000.
 N. Oldridge, M. Gottlieb, G. Guyatt, N. Jones, D. Streiner,
and D. Feeny, “Predictors of health-related quality of life
with cardiac rehabilitation after acute myocardial infarction,”
Journal of Cardiopulmonary Rehabilitation, vol. 18, no. 2, pp.
 S. H¨ ofer, W. Benzer, G. Sch¨ ußler, N. Von Steinb¨ uchel, and N.
B. Oldridge, “Health-related quality of life in patients with
coronary artery disease treated for angina: validity and relia-
bility of German translations of two specific questionnaires,”
Quality of Life Research, vol. 12, no. 2, pp. 199–212, 2003.
 T. K. Hillers, G. H. Guyatt, N. Oldridge et al., “Quality of life
after myocardial infarction,” Journal of Clinical Epidemiology,
vol. 47, no. 11, pp. 1287–1296, 1994.
on quality of life in elderly patients with ischemic dilated
cardiomyopathy,” Advances in Therapy, vol. 26, pp. 455–461,
 G. Y. Yeh, C. Wang, P. M. Wayne, and R. S. Phillips, “The effect
of Tai Chi exercise on blood pressure: a systematic review,”
Preventive Cardiology, vol. 11, no. 2, pp. 82–89, 2008.
of aerobic exercise and T’ai Chi on blood pressure in older
people: results of a randomized trial,” Journal of the American
Geriatrics Society, vol. 47, no. 3, pp. 277–284, 1999.
 W.-A. Lu and C.-D. Kuo, “The effect of Tai Chi Chuan on the
autonomic nervous modulation in older persons,” Medicine
and Science in Sports and Exercise, vol. 35, no. 12, pp. 1972–
 R. Hambrecht, E. Fiehn, J. Yu et al., “Effects of endurance
training on mitochondrial ultrastructure and fiber type distri-
bution in skeletal muscle of patients with stable chronic heart
failure,” Journal of the American College of Cardiology, vol. 29,
no. 5, pp. 1067–1073, 1997.
 M. H¨ ulsmann, M. Quittan, R. Berger et al., “Muscle strength
as a predictor of long-term survival in severe congestive heart
failure,” European Journal of Heart Failure, vol. 6, no. 1, pp.
 D. A. Skelton, A. Young, C. A. Greig, and K. E. Malbut,
“Effects of resistance training on strength, power, and selected
functional abilities of women aged 75 and older,” Journal of
the American Geriatrics Society, vol. 43, no. 10, pp. 1081–1087,
 M. J. Sullivan, M. B. Higginbotham, and F. R. Cobb, “Exercise
training in patients with severe left ventricular dysfunction:
hemodynamic and metabolic effects,” Circulation, vol. 78, no.
3, pp. 506–515, 1988.
 J. X. Li, D. Q. Xu, and Y. Hong, “Changes in muscle strength,
endurance, and reaction of the lower extremities with Tai Chi
intervention,” Journal of Biomechanics, vol. 42, no. 8, pp. 967–
 E. A. Christou, Y. Yang, and K. S. Rosengren, “Taiji training
improves knee extensor strength and force control in older
 F. Li, T. E. Duncan, S. C. Duncan, E. McAuley, N. R.
Chaumeton, and P. Harmer, “Enhancing the psychological
well-being of elderly individuals through Tai Chi exercise: a
latent growth curve analysis,” Structural Equation Modeling,
vol. 8, pp. 53–83, 2001.
 D. R. Brown, Y. Wang, A. Ward et al., “Chronic psychological
effects of exercise and exercise plus cognitive strategies,”
Medicine and Science in Sports and Exercise, vol. 27, no. 5, pp.
Canadian Journal of Research in Early Childhood Education,
vol. 6, pp. 341–352, 1998.