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666 The Journal of Rheumatology 2016; 43:3; doi:10.3899/jrheum.151110
Pers onal non -com merc ial use only. The Journal of Rheumatology Copyright © 2016. All rights reserved.
Improved Function and Reduced Pain after Swimming
and Cycling Training in Patients with Osteoarthritis
Mohammed Alkatan, Jeffrey R. Baker, Daniel R. Machin, Wonil Park, Amanda S. Akkari,
Evan P. Pasha, and Hirofumi Tanaka
ABSTRACT. Objective. Arthritis and its associated joint pain act as significant barriers for adults attempting to
perform land-based physical activity. Swimming can be an ideal form of exercise for patients with
arthritis. Yet there is no information on the efficacy of regular swimming exercise involving patients
with arthritis. The effect of a swimming exercise intervention on joint pain, stiffness, and physical
function was evaluated in patients with osteoarthritis (OA).
Methods. Using a randomized study design, 48 sedentary middle-aged and older adults with OA
underwent 3 months of either swimming or cycling exercise training. Supervised exercise training
was performed for 45 min/day, 3 days/week at 60–70% heart rate reserve for 12 weeks. The Western
Ontario and McMaster Universities Arthritis Index was used to measure joint pain, stiffness, and
physical limitation.
Results. After the exercise interventions, there were significant reductions in joint pain, stiffness, and
physical limitation accompanied by increases in quality of life in both groups (all p < 0.05). Functional
capacity as assessed by maximal handgrip strength, isokinetic knee extension and flexion power
(15–30% increases), and the distance covered in the 6-min walk test increased (all p < 0.05) in both
exercise groups. No differences were observed in the magnitude of improvements between swimming
and cycling training.
Conclusion. Regular swimming exercise reduced joint pain and stiffness associated with OA and
improved muscle strength and functional capacity in middle-aged and older adults with OA.
Additionally, the benefits of swimming exercise were similar to the more frequently prescribed
land-based cycling training. Trial registration: clinicaltrials.gov NCT01836380. (First Release January
15 2016; J Rheumatol 2016;43:666–72; doi:10.3899/jrheum.151110)
Key Indexing Terms:
ARTHRITIS AEROBIC EXERCISE ISOKINETIC MUSCLE STRENGTH
AQUATIC ACTIVITY
From the Cardiovascular Aging Research Laboratory, Department of
Kinesiology and Health Education, The University of Texas at Austin,
Austin, Texas, USA.
M. Alkatan, PhD; J.R. Baker, MS; D.R. Machin, PhD; W. Park, MS;
A.S. Akkari, BS; E.P. Pasha, MS; H. Tanaka, PhD, Cardiovascular Aging
Research Laboratory, Department of Kinesiology and Health Education,
The University of Texas at Austin.
Address correspondence to H. Tanaka, Department of Kinesiology
and Health Education, The University of Texas at Austin,
2109 San Jacinto Blvd., D3700, Austin, Texas 78712, USA.
E-mail: htanaka@austin.utexas.edu
Accepted for publication November 18, 2015.
Osteoarthritis (OA) is the most common form of arthritis and
is the leading cause of disability in older adults1. Because no
cure is currently available for OA, the treatment plan for this
prevalent, disabling, and costly disease has focused on
reducing joint pain and stiffness and improving physical
function while minimizing adverse effects. Although the
American College of Rheumatology has recommended that
aerobic exercise be included in OA treatment plans2, arthritis
and its associated joint pain and stiffness act as significant
barriers for those attempting to perform land-based
weight-bearing activities3,4. Additionally, the idea that
increased physical activity may result in greater wear and tear
on already-affected joints remains a substantial concern for
patients5,6. In this context, swimming appears to be the ideal
form of aerobic exercise for middle-aged and older patients
with OA. The minimal weight-bearing stress facilitated by
the buoyancy effects of water is an important element for
patients with OA who exhibit orthopedic hip and knee
problems. Additionally, many patients with OA are obese,
and obese patients are known to experience heat-related
problems when exercising in a hot environment7. Swimming
is characterized by a reduced heat load when participants are
surrounded by water8,9,10.
Because of these excellent traits of water-based exercise,
swimming has been widely recommended for the treatment
of OA. Surprisingly, however, no study to date has been
conducted to investigate the efficacy of swimming exercise
training in patients with OA. Thus, there is an urgent need to
conduct randomized clinical trials to determine whether
swimming exercise is truly beneficial to patients with OA.
Accordingly, the primary aim of our present study was to
determine the effects of swimming exercise training inter-
ventions on primary symptoms of OA (joint pain, stiffness,
and physical limitation) and functional capacity in
Rheumatology The Journal of on March 6, 2016 - Published by www.jrheum.orgDownloaded from
middle-aged and older patients with OA. Additionally, the
effect on quality of life was also addressed as a secondary aim
of the study. We included cycling training as a comparison
group because it is a land-based non–weight-bearing exercise
that has been shown to be effective in alleviating pain and
improving function in patients with OA11,12. Our working
hypothesis was that swimming exercise would produce
reductions in joint pain and stiffness and improvements in
functional capacity in patients with OA.
MATERIALS AND METHODS
Patients. Sedentary middle-aged and older adults (n = 48) with
Kellgren-Lawrence grade I-III radiographic OA were studied (Table 1).
Participants were recruited from orthopedic clinics and senior citizens’
centers in the local community through flyers, e-mails, and information
sharing and were screened for study participation. All power calculations
were performed using nQuery Adviser computer software. Sample size
calculations were based on the number of subjects needed to detect signifi-
cant changes in primary dependent variables [e.g., Western Ontario and
McMaster Universities Arthritis Index (WOMAC) pain and stiffness scales,
isokinetic muscle strength] from baseline levels in response to exercise
training. The estimated effect sizes for each dependent variable were based
on previous exercise studies in mainly middle-aged and older men and
women. The magnitude of these changes translates into effect sizes of 0.82
to 1.0. Therefore, with our estimate of 20 subjects/group, we should have >
80% power to detect the changes in each group. Exclusion criteria were (1)
having engaged in strenuous physical activity more than twice per week for
the previous year, (2) unstable cardiac or pulmonary diseases, (3) joint
replacement surgery during the past year, (4) intraarticular injection or
systemic corticosteroid usage within the past 6 months, (5) severe disabling
comorbidity that would disallow receiving exercise therapy, and (6)
aquaphobia. The majority of the subjects were white (~70%) and had OA in
lower limbs (~90%; Table 1). The Institutional Review Board at the
University of Texas at Austin reviewed and approved the study. All volun-
teers gave their written informed consent before participation.
Exercise training intervention. Following baseline measurements, partici-
pants were randomly assigned by a blinded investigator to either swimming
(n = 24) or cycling (n = 24) exercise training groups according to sequen-
tially numbered, sealed, opaque envelopes indicating treatment allocation
(Figure 1). Supervised exercise training conformed to guidelines established
by the American College of Sports Medicine13. For the first few weeks of
the supervised exercise training, participants received active coaching and
instruction by a member of the research team. Initially, participants exercised
for 20–30 min/day, 3 days/week at an exercise intensity of 40-50% of heart
rate reserve (HRR). HRR was calculated using this equation: (maximal heart
rate – resting heart rate) + resting heart rate14 and was monitored daily. As
each participant’s level of fitness improved, the intensity and duration of
exercise increased with the goal of attaining 40-45 min/day, 3 days/week at
an intensity of 60-70% of HRR. Exercise training lasted 12 weeks. During
the course of the investigation, participants were instructed to maintain their
usual lifestyle and dietary habits.
The swimming training was performed in the swimming pools (25-yard
length) located in Gregory Gymnasium on The University of Texas at Austin
campus. Water temperature of the swimming pool was held constant at
27–28°C. All the swimming sessions were supervised by an investigator who
was certified as a Red Cross Water Safety and Red Cross Lifeguard
instructor. Subjects used freestyle, breast stroke, or a combination. One
subject had no previous swimming experience. For this subject, one-on-one
learn-to-swim coaching was combined with swimming with a kick board
and fins to maintain the heart rate within the prescribed zone. The cycling
training was performed on a stationary cycle ergometer in the Exercise
Training Intervention Core Laboratory on The University of Texas at Austin
campus and was supervised by an investigator who was a certified personal
trainer. Each participant received instructions to exercise continuously except
during the time needed for checking a target heart rate by heart rate monitor
(Polar Electro) secured on each participant’s chest. Heart rate monitors were
waterproof and suitable for both cycling and swimming exercises.
Testing sessions. At baseline and postintervention, measurements were
performed in the same order and at the same time of day on each participant
after the participant had refrained from alcohol and exercise for at least 12
h prior to arrival. All prescription and over-the-counter medicines and
supplements were identical for 7 days prior to the pretesting and posttesting
sessions. To avoid the acute effect of exercise, participants were studied at
least 48 h after their last exercise training session for the postintervention
testing session. In an attempt to minimize the “learning effects” or “training
effects” involved in repeated tests, familiarization sessions were conducted
prior to the start of the exercise intervention. Prior to the pretesting, each
subject was fully familiarized with the measurements and performed
repeated trial runs. Investigators were blinded to the group assignment.
Body mass and composition. Height and body mass were measured with a
physicians’ balance scale (Seca) while the participants were barefoot and in
light clothing. Body mass index was calculated using the equation body mass
(kg)/height squared (m2). Body fat percentage, lean tissue mass, and visceral
adipose tissue were determined noninvasively using dual-energy x-ray
absorptiometry (GE Lunar Radiation)15.
Physical activity. Measurements of physical activity were performed using
the Godin physical activity questionnaire16.
Physical performance. Physical performance was determined with the 6-min
walk test17. Participants received instructions to walk as far as possible in 6
min on a flat, indoor surface and did not receive feedback or encouragement
during the test but were allowed to rest if needed. Footwear was recorded at
the baseline testing session and replicated post intervention. Additionally,
during each testing visit the participant was equipped with a pedometer
(Omron HJ-324U) to assess the number of steps and stride lengths18.
Muscle strength and power. To determine upper body muscular strength,
maximal isometric grip strength of both arms was assessed unilaterally using
a standard grip strength dynamometer. To determine lower body muscular
strength, isokinetic knee flexor and extensor strengths of both legs were
assessed unilaterally at an angular velocity of 60°/s and 120°/s19 using an
isokinetic dynamometer (Biodex Medical Systems), which was calibrated
before every testing session. The pelvis, trunk, and thighs were stabilized
with straps. Participants were asked to cross their arms on their chest during
testing and perform 3 submaximal practice repetitions. This was followed
by 5 maximal repetitions of flexion and extension in both legs, and no
encouragement was provided. The peak torque reported was the average of
the highest right and left scores of the 5 maximal efforts. The reliability
values ranged from 0.88-0.97.
Pain and disease severity. Physical function, stiffness, and pain were
667
Alkatan, et al: Swimming, cycling, and OA
Table 1. Participant demographic and clinical characteristics.
Variable Cycling Swimming
Race and ethnicity, n
White 18 16
African American 34
Hispanic 33
Asian 00
Other 01
Affected joints, n
Foot 22
Hand 21
Hip 32
Knee 15 18
Shoulder 10
Spine 10
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evaluated using the WOMAC Index, a self-administered questionnaire. The
WOMAC has been widely used in the evaluation of OA and consists of 24
items on a 5-point Likert scale (0 = none, 1 = mild, 2 = moderate, 3 = severe,
4 = extreme) that deal with participant’s perception of pain, joint stiffness,
and physical function20.
Life quality. Health-related quality of life (HRQOL) was assessed with a
validated self-report questionnaire, the Medical Outcomes Study Short
Form-36 (SF-36; Medical Outcomes Trust), which consists of 36 questions
that evaluate physical and mental HRQOL21.
Statistical analyses. Chi-squared test was used to analyze categorical
variables, and continuous baseline variables were analyzed using an
independent sample t test or the Mann-Whitney U test, based on the results
from a Shapiro–Wilk test of normality. Data were analyzed using an
intent-to-treat analysis with a longitudinal modeling with random effects for
all 48 randomized participants22. The longitudinal modeling allows all
observed repeated measures to be included in the analyses and may be suited
for exercise intervention trials22. We also determined that the subjects who
dropped out of the exercise training program were not systematically
different from those who remained and completed the program. To ensure
the validity of the intention-to-treat analysis, we also conducted a per-
protocol analysis of the 40 participants who completed the exercise inter-
vention23. Intention-to-treat analysis of 48 participants, including 8 dropouts,
was consistent with the per-protocol analysis of the 40 participants who
completed the exercise interventions. Accordingly, we have reported results
only from the intention-to-treat analysis. A 2-way (time × group) repeated
measures ANOVA was performed to compare outcomes of interest, with
statistical significance set at an α-level of 0.05. When a significant main
effect of time, treatment, or treatment × time interaction was detected, paired
668 The Journal of Rheumatology 2016; 43:3; doi:10.3899/jrheum.151110
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Figure 1. Participant flow through the trial.
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samples t tests were used to assess intragroup differences at baseline and
later.
Because our present study was not adequately powered to detect signifi-
cant group differences, changes in key dependent variables with each
exercise training were emphasized. All statistical analyses, including the
imputation of missing values, were performed with SPSS Version 22.0
software (SPSS Inc.). Data are presented as mean ± SEM.
RESULTS
Selected participant demographic and clinical characteristics
at baseline are presented in Table 1. Cycling and swimming
groups were not different in age (61 ± 1 vs 59 ± 2 yrs), race,
ethnicity, sex distribution (2 men and 22 women in both
groups), education (16 ± 1 vs 16 ± 1 yr), and OA-affected
joints. Among the 48 participants randomly assigned to the
groups, 4 participants in each group dropped out prior to the
end of the intervention (mostly owing to a lack of time, job
conflict, etc.). The remaining participants had excellent atten-
dance and adherence to swimming (98%) and cycling (97%)
exercise training.
At baseline, there were no significant differences in
physical characteristics and body stature between participants
in the swimming and cycling exercise groups (Table 2). After
the 12-week exercise intervention, body mass, visceral
adiposity, and waist and hip circumference were decreased
in both exercise training groups (all p < 0.01). There were no
significant differences in the magnitude of the reductions
between the 2 training groups (p = 0.13).
As shown in Table 3, there were reductions in joint pain,
stiffness, and functional limitation, as determined by the
WOMAC index, in both exercise groups (all p < 0.001).
Participants in both swimming and cycling exercise training
groups demonstrated significant increases in distance covered
during the 6-min walk test (p < 0.001; Table 4). Maximal grip
strength and isokinetic knee extensor and flexor strength
increased in both swimming and cycling exercise training
groups (all p < 0.05; Table 4 and Figure 2).
DISCUSSION
Our present study is the first, to our knowledge, to demon-
strate the benefit of swimming exercise training for treatment
of OA. Swimming has been recommended widely and
consistently by various medical organizations for the
management of OA2,24,25, but the efficacy of swimming in
patients with OA has never been studied. We found that 3
months of swimming exercise training produced substantial
reductions in joint pain (~40%), stiffness (~30%), and
functional limitation (~25%) in patients with OA. Addi-
tionally, these changes were accompanied by the improve-
ments in physical performance, upper and lower body muscle
strength, as well as reductions in body mass, and joint stiffness.
In general, the benefits gained from the water-based exercise
were similar to the land-based control modality of cycling, so
that the benefits for this population are well established11,12.
Joint pain and stiffness are the most common symptoms
in patients with OA and are the primary barriers for
performing activities of daily living in this patient
population3. The present results demonstrate that
non–weight-bearing exercise performed in water led to ~40%
reductions in joint pain that patients with OA experience
while performing daily activities on land. Additionally,
regular swimming produced ~30% reductions in joint stiff-
ness and ~25% decrease in functional limitation. The
magnitude of these reductions in WOMAC scores exceeds
minimal clinically important improvement threshold either
expressed as 17% difference26 or 0.51 to 1.33 points27.
Most patients with OA spend most of their time on land
performing the activities of daily living. Because of the
principle of the specificity of exercise training28, it was not
known whether the functional benefits gained in water would
be translated into better physical function in normal daily life
on land. In our present study, we assessed muscular strength,
as determined by isokinetic quadriceps and hamstring
strength, and handgrip strength. All the muscle strength
measures improved significantly after the swimming inter-
vention. Additionally, physical performance, as determined
by the 6-min walk distance, improved significantly by 6%
and 8% in the cycling and swimming groups, respectively.
Importantly, improvements in muscular strength and physical
function achieved by swimming were similar to those elicited
by cycling exercises performed on land.
Although there were no significant differences between
669
Alkatan, et al: Swimming, cycling, and OA
Table 2. Changes in selected participant characteristics. Values are mean ± SEM.
Variables Cycling Swimming
Baseline After Baseline After
Body mass, kg 84.5 ± 3.8 83.0 ± 4.1* 92.0 ± 4.7 89.4 ± 3.9*
Body mass index, kg/m231.6 ± 1.7 31.0 ± 1.9 34.6 ± 2.1 33.9 ± 1.7
Waist circumference, cm 102 ± 4 99 ± 4* 106 ± 3 103 ± 3*
Hip circumference, cm 116 ± 3 114 ± 3* 120 ± 3 117 ± 3*
Body fat, % 44 ± 2 44 ± 2 45 ± 2 44 ± 2
Lean tissue mass, kg 96 ± 4 97 ± 4 102 ± 3 101 ± 3
Visceral adipose tissue, kg 3.3 ± 0.4 3.2 ± 0.4* 3.4 ± 0.3 3.0 ± 0.3*
Godin physical activity score, U 15 ± 2 35 ± 1* 13 ± 1 38 ± 2*
* p < 0.05 versus baseline.
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swimming and cycling exercise training groups, this does not
diminish the clinical importance of our study — it enhances
it. A number of studies have shown a benefit of land-based
exercise intervention compared with sedentary control condi-
tions in patients with OA29,30. While we considered adding a
sedentary (non-exercising) control condition, we determined
670 The Journal of Rheumatology 2016; 43:3; doi:10.3899/jrheum.151110
Pers onal non -com merc ial use only. The Journal of Rheumatology Copyright © 2016. All rights reserved.
Table 3. Changes in physical function, pain, and health-related quality of life. Values are mean ± SEM.
Variables Cycling Swimming
Baseline After Baseline After
WOMAC
Pain (0–20) 7.8 ± 0.9 4.5 ± 0.5* 6.9 ± 0.7 4.2 ± 0.5*
Stiffness (0–8) 4.4 ± 0.4 3.1 ± 0.3* 3.8 ± 0.3 2.6 ± 0.3*
Functional limitation (0–68) 23.5 ± 1.8 17.5 ± 2.7* 20.9 ± 2.1 11.7 ± 1.9*
Health-related quality of life (SF-36)
Mental score (0–100) 64 ± 4 78 ± 3* 65 ± 3 79 ± 3*
Physical score (0–100) 51 ± 4 69 ± 3* 53 ± 4 73 ± 3*
* p < 0.05 versus baseline. WOMAC: Western Ontario and McMaster University Osteoarthritis Index; SF-36:
Medical Outcomes Study Short Form-36.
Table 4. Changes in physical function and muscle strength tests.
Variables Cycling Swimming
Baseline After Baseline After
Six-min walk test, m 552 ± 22 594 ± 19* 556 ± 21 589 ± 22*
Six-min walk test, steps 775 ± 12 879 ± 13* 782 ± 18 890 ± 16*
Walk speed, m/s 1.5 ± 0.06 1.7 ± 0.06* 1.5 ± 0.06 1.6 ± 0.1*
Grip strength left, kg 21.8 ± 1 23.0 ± 1* 20.6 ± 1 21.3 ± 1*
Grip strength right, kg 22.8 ± 1 24.6 ± 1* 20.2 ± 1 20.6 ± 1*
Isokinetic knee peak torque at 60°/s
Right-extension, Nm 62 ± 5 72 ± 5* 58 ± 4 68 ± 4*
Right-flexion, Nm 41 ± 4 50 ± 3* 42 ± 3 50 ± 3*
Left-extension, Nm 58 ± 4 64 ± 4* 60 ± 3 69 ± 4*
Left-flexion, Nm 41 ± 5 50 ± 3* 42 ± 3 50 ± 3*
Isokinetic knee peak torque at 120°/s
Right-extension, Nm 46 ± 4 55 ± 4* 40 ± 3 48 ± 3*
Right-flexion, Nm 35 ± 3 41 ± 3* 32 ± 2 40 ± 2*
Left-extension, Nm 44 ± 3 53 ± 3* 44 ± 2 56 ± 3*
Left-flexion, Nm 35 ± 3 40 ± 3* 33 ± 2 44 ± 2*
Values are mean ± SEM. * p < 0.05 versus baseline.
Figure 2. Relative percent increases in isokinetic knee extensor and flexor peak torque at an angular velocity of 60°/s (left panel)
and 120°/s (right panel; average of right and left legs). Values are mean ± SEM. All p < 0.05.
Rheumatology The Journal of on March 6, 2016 - Published by www.jrheum.orgDownloaded from
it to be unethical to forgo an effective treatment for patients
with OA. We are aware that some studies have used a waiting
list–type sedentary control prior to entrance into the
study31,32, but we decided against implementing it, because
the integrity of a truly randomized study design, one of the
most important aspects of any clinical trial, would have been
lost with such a study design. Thus, we decided to use cycling
as a land-based non–weight-bearing exercise training com-
parison group because it has been shown to be effective in
reducing pain, but more importantly is well-tolerated in
patients with OA11,12.
Our present study was the first, to our knowledge, to
investigate the effects of swimming exercise in patients with
OA. However, several studies have compared aquatic
exercises (e.g., water aerobics) to land-based exercises9,33.
These studies found that both land-based and aquatic
exercises reduced pain and improved physical function in
patients with OA. Although land-based exercise might be
more convenient to perform, there may be psychological
barriers, because patients with OA have enormous difficulty
performing weight-bearing physical activity in their daily life
owing to joint pain, joint stiffness, and muscle weakness34,35
that could be aggravated by exercises, leading them to a
sedentary lifestyle3or to limit their daily physical activity to
the minimum4. In light of this, water-based exercises would
be an ideal form of physical activity for patients with OA
because of the minimal weight-bearing stress, humid
environment, and reduced heat load8,9. Although swimming
and aquatic exercise take place in water and are well received
by patients with OA, these water-based exercises differ
significantly in regard to body position, muscle groups used,
and sustainable exercise intensity. Yet they are often cate-
gorized into the same exercise mode, although the land-based
counterparts of aerobic dancing and jogging/running are
hardly clustered together. Further studies are needed to
compare swimming and aquatic exercise or to investigate the
effect of the combination of swimming and aquatic exercise
in treatment of OA.
There were several limitations to our study. Participants
performed supervised exercise for only 3 months in this time
span. Although we observed health benefits of exercise
training in this time, it is unknown whether continued partici-
pation in exercise training would maintain or enhance these
benefits. An additional limitation is the lack of participant
blinding to treatment allocation. Swimming is considered an
ideal form of exercise for patients with OA. Placement in the
alternate exercise condition may have affected self-reported
outcomes or motivation. This is, however, unlikely because
the number of dropouts were equal between exercise inter-
ventions. Lastly, we included only patients with mild to
moderate radiographic OA. Not included were patients with
advanced stages of OA who were using a walker or awaiting
a joint replacement. Thus, we cannot generalize the present
findings to that population. Future studies should investigate
the benefits of exercise training in these patients; they would
likely benefit from a swimming or cycling exercise program.
Our results indicated that 3 months of non–weight-bearing
exercise training, including swimming and cycling, reduced
joint pain, stiffness, and functional limitation and improved
physical performance and functional capacity in patients with
OA. Not only are these the first findings, to our knowledge,
to indicate the efficacy of swimming exercise for patients
with OA, but they also demonstrate that swimming exercise
exerts functional benefits similar to the more frequently
prescribed land-based cycling training. Future studies should
investigate whether other benefits of swimming exercise (i.e.,
improved cardiovascular outcomes) are present after swim-
ming exercise training in patients with OA.
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