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                                      Journal of Exercise Physiologyonline

                                                 Volume 15 Number 2 April 2012



Editor-in-Chief                                              JEPonline
Tommy Boone, PhD, MBA
Review Board
Todd Astorino, PhD
                                Twelve Weeks of Aqua-Aerobic Exercise Improve
Julien Baker, PhD               Physiological Adaptations and Glycemic Control in
Steve Brock, PhD                Elderly Patients with Type 2 Diabetes
Lance Dalleck, PhD
Eric Goulet, PhD
Robert Gotshall, PhD            Apiwan Nuttamonwarakul1, S. Amatyakul2, D. Suksom3
Alexander Hutchison, PhD
                                1
M. Knight-Maloney, PhD           Inter-department of Biomedical Sciences, Chulalongkorn University,
Len Kravitz, PhD                Bangkok, Thailand, 2Department of Physiology, Faculty of Dentistry,
James Laskin, PhD
                                Chulalongkorn University, Bangkok, Thailand, 3Faculty of Sports
Yit Aun Lim, PhD
Lonnie Lowery, PhD              Science, Chulalongkorn University, Bangkok, Thailand
Derek Marks, PhD
Cristine Mermier, PhD                                        ABSTRACT
Robert Robergs, PhD
Chantal Vella, PhD
                                Nuttamonwarakul A, Amatyakul S, Suksom D. Twelve Weeks of
Dale Wagner, PhD
Frank Wyatt, PhD                Aqua-Aerobic Exercise Improve Physiological Adaptations and
Ben Zhou, PhD                   Glycemic Control in Elderly Patients with Type 2 Diabetes. JEPonline
                                2012;15(2):64-70. Aqua-aerobic exercise (AE) has been proposed as
                                an alternative mode of exercise in the medical management of type 2
 Official Research Journal of
                                diabetic (T2DM) patients. The purpose of this study was to investigate
   the American Society of
Official Research Journal
    Exercise Physiologists      the effects of a 12-wk AE training program on physiological
of the American Society of      adaptations and glycemic control in older subjects with T2DM. Forty
  Exercise Physiologists
     ISSN 1097-9751             elderly subjects with diagnosis of T2DM were assigned either to the
                                AE group (n=20) or the non-exercise control group (n=20). The AE
   ISSN 1097-9751               group performed aerobic exercise in the swimming pool (water temp
                                ~34 to 36°C), which consisted of 3 days/wk at 70% of maximum heart
                                rate for 30 min. The aqua-aerobic training group demonstrated a
                                significant increase in VO2 max, and a significant reduction in body
                                weight, percentage of body fat, blood pressure, and resting heart rate
                                at the 12th week of training (P<0.05). Glycosylated hemoglobin
                                (HbA1c), cholesterol, triglyceride, and insulin decreased significantly
                                (all P<0.05) in the AE group compared to the non-exercise control
                                group. These findings indicate that 12 wks of AE training may help
                                prevent complications in elderly patients with T2DM.

                                Key Words: Water-Based Training, Hyperglycemia, Ageing, Fitness
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INTRODUCTION

Type 2 diabetes mellitus (T2DM) is expected to increase by 46% around the world, and the incidence
of T2DM is increasing rapidly as a result of the ageing population. It is one of the fastest growing
public health problems, which is associated with numerous complications (e.g., retinopathy,
nephropathy, and atherosclerotic heart disease) that result from prolonged hyperglycemia (10).

Aquatic exercise has been found to slow the age-associated physiological declines and decrease the
risk for T2DM by improving the circulation, muscle strength, and endurance (12,16). Scientific reports
are also available on the renal-endocrine response during water immersion at rest and during water-
based exercise in older adults (14,15). Aquatic exercise training improves glucose uptake by lowering
both insulin resistance and body fat in subjects with T2DM. However, there are only a few reports that
describe the long-term effects of aquatic exercise in older adults. In particular, more information is
needed in regards to the effects of a regular aquatic exercise program on physiological adaptations
and glycemic control in the elderly T2DM subjects.

The purpose of this study was to investigate the effects of 12-wks aqua-aerobic exercise training on
the physiological adaptations and glycemic responses in elderly subjects with T2DM.

METHODS
Subjects
Forty subjects with T2DM (who were over 60 yrs of age) were recruited from the Ageing Center of the
local community, Thailand. The subjects were randomly divided into the aquatic exercise group (AE;
n=20) and the non-exercise control group (NC; n=20) group in a 12-wks program. All subjects were
medically screened before participation and no medications were altered during the exercise training
period. The experimental protocol was approved by the supreme patriarch center on aging research
and ethics committee, Ministry of Public Health. Explanation on experimental procedures, possible
risks and benefits of participating in the study were done prior to the subjects’ signing the informed
consent form.

Procedures
The AE group participated in a 12-wk aquatic exercise program 3 day·wk-1 for 50 min per day with an
average water temperature of ~34 to 36°C. Each session was led by one of the researchers. Prior to
each exercise class, the subjects were asked to avoid vigorous physical activity, caffeine, and
alcoholic beverages. They were also asked to eat regular meals with an appropriate amount of water
and sleep-rest period. The AE program consisted of 10 min of stretching and warm-up exercises
followed by 30 min of aquatic exercise at 70% of maximum heart rate (HR) and, then, cool-down
exercises for 10 min. The HR was monitored continuously for all subjects during the training sessions
by a HR monitoring device (Polar team 2pro, Finland) to ensure that the training intensity was
maintained as prescribed.

The subjects were asked to report abnormal signs and symptoms, and understood that at any time
they experienced uncomfortable feeling they could stop exercising. Subjective estimation of working
load was carried out using rating of perceived exertion (RPE) scale. All parameters were assessed
before and after the 12-wk aquatic exercise training. Resting HR and blood pressure were taken after
10 min of quiet sitting. Body weight, height, and percentage of body fat were also measured. Body
composition was measured by the bioelectrical impedance method (RJL System, Detroit, MI, USA).
Maximal oxygen uptake (VO2 max) was determined using a gas analyzer (Cosmed, Rome, Italy) with
the modified Bruce treadmill (Quinton, USA) protocol. Perceived exertion was rated every minute
                                                                                                       66

using the Borg scale. The attainment of VO2 max was validated if two of the following four criteria
were satisfied: (1) oxygen uptake plateau despite increasing exercise intensity (≤120 mL·min-1); (2)
respiratory exchange ratio ≥1.15; (3) maximal heart rate within 10 beats·min-1 of the age-predicted
maximal value; and (4) a Borg scale value ≥17. Venous blood was drawn after an 8-hr overnight fast.
The resulting serum was immediately analyzed by a certificated clinical laboratory for glycosylated
hemoglobin (HbA1c), cholesterol, triglyceride, and insulin.

Statistical Analyses
All values were presented as means ± SD. The differences of various parameters between pre- and
post-test exercise training were analyzed by paired t-test. Student’s t-test was used for comparing
data between groups. The P value, set a priori, of <0.05 was considered statistically significant.

RESULTS

Physiological Data
After the 12 wks, only the AE group showed a significant decrease (P<0.05) in body weight,
percentage body fat, systolic blood pressure, diastolic blood pressure, and resting HR. Maximum
oxygen consumption (VO2 max) was significantly increased from baseline (P<0.05) in only the AE
group (Table 1).


Table 1. Physiological Adaptations after 12 wks of Training.
                          Aquatic Exercise Group                          Control Group
    Variables                    (n=20)                                        (n=20)
                           Baseline         After 12 wks           Baseline             After 12 wks

Body weight                62.88.6           61.18.3*           61.110.6              61.410.7
(kg)
Body fat                   39.45.5           38.55.8*            36.54.9               37.15.0
(%)
SBP                       117.615.0         115.213.4*          114.29.5             114.512.2
(mm Hg)
DBP                       74.711.6           71.78.3*            70.76.8               73.46.0
(mm Hg)
HR rest                   82.311.3          73.37.8*,**          78.67.9              80.77.2**
(beats·min-1)
VO2max                     24.92.8           25.12.0*            24.52.7               24.12.3
       -1       -1
(mL·kg ·min )
Values are mean  SD. SBP; Systolic Blood Pressure, DBP; Diastolic Blood Pressure, HR; Heart
rate, VO2 max; Maximal oxygen uptake. *represents statistical difference from pretest at P<0.05
and **represents statistical difference between groups at P<0.05.
                                                                                                       67

Blood Chemistry Parameters
Glycosylated hemoglobin (HbA1c), cholesterol, triglyceride, and insulin were significantly decreased
(P<0.05) only in the AE group. There were no significant changes in these variables in the NC group
(Table 2).

Table 2. Changes in Blood Chemistry Parameters after 12 wks of Training.
                         Aquatic Exercise Group                  Control Group
      Variables                          (n=20)                                     (n=20)
                         Baseline             After 12 wks             Baseline         After 12 wks

HbA1c                     7.71.1              6.60.7*,**              7.60.2            7.60.3**
(%)
Cholesterol             231.630.0            221.029.6*             232.150.0          231.349.3
(mg/dL)
Triglyceride            178.782.3            161.973.9*             177.160.1          176.259.1
(mg/dL)
Insulin                  23.64.1               22.53.4*              22.15.1            22.55.3
(µU/mL)
Values are mean  SD. FBG; Fasting blood glucose, HbA1c; glycosylated hemoglobin. *represents
statistical difference from pretest at P<0.05 and **represents statistical difference between groups
at P<0.05.


DISCUSSION

Twelve weeks of aqua-aerobic exercise (AE) training significantly improved in the physiological
adaptations and glycemic control in subjects older than 60 yrs of age by reducing weight, percentage
body fat, blood pressure, and increasing VO2 max. Also, there were improvements in HbA1c,
cholesterol, triglyceride, and insulin. These results are supported by previous reports (4,6,17) that
concluded deep water running is effective in maintaining and improving cardiovascular fitness (as well
as resistance-type shallow water exercise improving strength and functional mobility). In the present
study, the AE group showed a significant difference in HbA1c when compared to the control group. It
is clear that the AE training protocol was sufficient to improve the physiological status of older
subjects with T2DM.

The decreases in body weight and percentage of body fat after 12 wks of aquatic exercise training
are favorable changes in subjects with T2DM. The effects of exercise training in water on body
composition have been controversial in several studies. Some investigations did not detect significant
change after aquatic training while others reported a reduction in body fat (3). This may be due to the
different methods used to assess body composition and/or different training regimens (i.e., aerobic
training vs. resistance training).

Low cardiorespiratory fitness (as defined by VO2 max) is prevalent among individuals at high risk for
T2DM. Therefore, a significant increase in VO2 max (i.e., even a small increase) at 12 wks of AE
training should be viewed as a positive physiological response (in terms of cardiovascular disease).
Clearly, exercise programs for diabetic patients should consist of a 5 to 10 min warm-up and cool-
                                                                                                     68

down to improve cardiovascular performance. Then, the recommended frequency of exercise is
should be between 3 to 5 sessions per week with at least 30 min of continuous and moderate
exercise in each training session (1,2).

The incremental speed of underwater movements in the present study improved physiological
adaptation and cardiovascular responses, which are consistent with the findings of earlier studies.
Changes in resting heart rate and blood pressure (systolic and diastolic blood pressures) at 12 wks of
training in the AE group were also found. Aqua-aerobic exercise training, when properly supervised,
is an excellent type of exercise to improve the hemodynamic responses of T2DM subjects. This was
demonstrated with the decrease in the subjects’ HR and the improvement in the sensitivity of the
aortic baroreceptors, which contributed to a more efficient regulation of blood pressure (7,9,11).
Moreover, the hydrostatic pressure of being in the water helped to increase the venous return to the
heart and, thus improve the subjects’ blood circulation (8).

Changes in glycemic control that resulted from the 12-wk aqua-aerobic exercise training are indicated
in the significant decreases in HbA1c, cholesterol, triglyceride, and insulin. Aquatic exercise improved
the subjects’ glycemic control, which has been reported in a randomized controlled trial in 251 T2DM
patients. The authors reported improvements ranging from -0.38 to -0.97 percentage points in HbA1c
from exercise training that ranged from 135 to 270 min of exercise per week for 6 months (13). A
similar result was reported in a meta-analysis of 15 papers that suggested regular exercise in patients
with T2DM can lose weight and improve HbA1c values (5). Patients T2DM who can improve glycemic
control demonstrate decreased rates of chronic complications such as neuropathy, retinopathy,
nephropathy, and cardiovascular disease.

CONCLUSIONS

Twelve wks of aqua-aerobic exercise training improves cardiovascular fitness, glycemic control, and
physiological adaptations in older adults with T2DM. Moreover, it may provide additional benefits by
reducing the incidence of falls and injuries that occur while performing exercise or while performing
activities of daily living. Therefore, it is more than reasonable to conclude that aquatic exercise is a
beneficial mode of exercise for elderly patients with type 2 diabetes.


ACKNOWLEDGMENTS
This study was supported by the 90th anniversary of Chulalongkorn University (Ratchadaphisek
somphot endowment fund).

Address for correspondence: Nuttamonwarakul A., Inter-department of Biomedical Sciences,
Chulalongkorn University, Thailand, 10330. Phone (+66)2 256-4493 Ext. 12; FAX: (+66)2 256-4493
Ext. 17; Email. Apiwan1@gmail.com


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