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1295
Official Journal of ISPAH
www.JPAH-Journal.com
ORIGINAL RESEARCH
Journal of Physical Activity and Health, 2014, 11, 1295 -1303
http://dx.doi.org/10.1123/jpah.2012-0426
© 2014 Human Kinetics, Inc.
Moussouli, Vlachopoulos (vlachop@phed-sr.auth.gr), Kofotolis, and
Kellis are with the Dept of Physical Education and Sport Science at Serres,
Aristotle University of Thessaloniki, Serres, Greece. Theodorakis is with
the Dept of Physical Education and Sport Science, University of Thessaly,
Trikala, Greece. Malliou is with the Dept of Physical Education and Sport
Science, Democritus University of Thrace, Komotini, Greece.
Effects of Stabilization Exercises on Health-Related Quality of Life
in Women With Chronic Low Back Pain
Maria Moussouli, Symeon P. Vlachopoulos, Nikolaos D. Kofotolis, Yannis Theodorakis,
Paraskevi Malliou, and Eleftherios Kellis
Background: The study examined the effects of a 4-week intensive isometric and isotonic stabilization exercise program on
dimensions of health-related quality of life (HRQL) in women with chronic low back pain (CLBP). Methods: A total of 39
women (27–72 years old) provided data in an experimental study with a 9-month follow-up. Random allocation was undertaken
for the two treatment groups out of the 3 groups: isometric stabilization (n = 13), isotonic stabilization (n = 13), and a control
group (n = 13) that did not participate in any form of exercise. Health-related quality of life measures using the Short-Form 36
Health Survey were assessed before program initiation, immediately after program termination, and 4 times postintervention
for a period of 9 months. Results: The isometric stabilization group displayed large improvements in bodily pain and vitality
for women with CLBP attending a 4-week intensive isometric stabilization exercise program. The effects were retained for a
period of 9 months after program termination. Conclusions: Isometric stabilization exercises reduce pain and enhance vitality
as dimensions of HRQL among women with chronic low back pain with such effects lasting for at least 9 months.
Keywords: isometric, isotonic, physical activity
While musculoskeletal diseases are the fth most expensive
disease category in terms of hospital care and the most expensive
in relation to work absenteeism and disablement, one-half of such
costs are due to back pain.1 Low back pain may lead to physical and
psychological problems, disability, and deterioration of the quality
of life. As one of the important goals of healthcare is promoting a
prolonged life, maintaining a health-related quality of life (HRQL)
has gained increasing recognition as an important concept and index
of chronic care.2
A number of interventions used to treat low back pain include
the use of physical exercise aiming to activate abdominal and/or
back extensor muscles with the goal of reducing pain and disabil-
ity.3–5 Stabilization exercises have been used in this respect.4–8 A
few randomized clinical trials have examined the effectiveness of
stabilization exercises concluding that stabilization exercises can
reduce pain and disability in patients with chronic low back pain
(CLBP).9–12 However, their effect was not as large when compared
with active treatment control groups indicating that more studies are
required to determine their effectiveness. Further, some evidence
has emerged against the effectiveness of stabilization exercises13,14
while other studies have reported the opposite.15,16 This inconclusive
evidence led May and Johnson9 to conclude that “there may be a
role for specic stabilization exercises in some patients with chronic
low back pain, but these are no more effective than other active
interventions” (p.1). Consequently, the effectiveness of stabilization
exercises for treating low back pain remains unclear.
Two common forms of trunk stabilization exercises are exercises
that consist of isometric (static) contractions of the involved muscu-
lature as well as exercises that involve dynamic contractions (will
be referred to as “isotonic” exercises).4,17,18 Isometric exercises are
mainly based on cocontraction of antagonistic muscle groups around
the trunk while the body holds a static position. Isotonic exercises
involve contraction of muscles through a predened range of motion
and resemble more the “classic” general type of exercises, but the
involvement of body motion makes them more functional. The
effectiveness of each type of exercise is unclear and this may be due
to large variations in the design of treatment programs published
in various studies as well as the use of stabilization exercises in
combination with other treatment therapies.9,12 Comparison of the
effects of an isometric proprioceptive neuromuscular facilitation
(PNF) training program with those of an isotonic exercise program
indicated improvements in trunk muscular endurance and trunk
mobility in CLBP patients after both programs.19 However, this
study employed only a short-term follow-up period (8 weeks post
training) and exercises were performed against resistance provided
by a therapist; however, changes in HRQL as a result of exercise
were not monitored.
While research has examined the effectiveness of trunk exercises
on functional performance, fewer studies have examined the impact
of stabilization exercises on HRQL.12,14,20–22 In a comprehensive
review, Ferreira et al12 concluded that stabilization exercise programs
improve marginally health-related quality of life. However, evidence
was based on only 1 randomized trial.21 More recent evidence has
indicated that trunk balance exercises combined with exibility exer-
cises were found to be more effective compared with a combination
strength and exibility exercise program in reducing disability and
improving the physical component of quality of life.20 Similar results
have been also reported when stabilization exercises were added to
conventional physical therapy exercises in the treatment of patients
with recurrent low back pain.14 Moreover, a 3-month intervention
consisting of lumbar stabilization exercises and specically the
abdominal drawing-in-maneuver and prone kneeling reduced chronic
low back pain and improved quality of life in patients with CLBP.22
1296 Moussouli et al
It is still not known (a) which specic types of stabilization
exercises are more effective in reducing pain and improving HRQL;
(b) among which types of populations such effects hold; and (c) the
extent to which such benets may be maintained after termination
of intervention. The current study examined the effects of 2 types
of spinal stabilization exercises (isotonic stabilization exercise
and isometric stabilization exercise) on physical and mental health
dimensions of HRQL including pain among middle-age women
with CLBP. Considering previous evidence in which the isotonics
program led to a greater reduction in back pain intensity compared
with isometric stabilization,19 it was hypothesized that it would be
the isotonic program that would lead to a greater reduction in low
back pain and greater improvements in the physical and mental
health components of HRQL.
Methods
Design
A total of 43 women with CLBP were recruited from 2 communities
in the same geographical area in northern Greece. Participants of
one community were randomly assigned into 1 of the 2 treatment
groups (isometric spinal stabilization exercises and isotonic spinal
stabilization exercises) with 13 participants per group while 13
participants from the second community served as the control group
(see Figure 1 for participant owchart). These participants were
randomly selected out of 17 women with CLBP to achieve a roughly
equal number of participants per group in the study. The reason
that led to such a design was the limited number of women with
CLBP in the rst community and the obstacle of traveling distance
from one community to the other. The program was designed to be
an intensive program of 4 weeks duration consisting of 4 exercise
sessions per week. Therefore, it comprised 16 exercise sessions
completed in a 1-month period. Baseline (pre) HRQL measure-
ments were recorded after assignment to the groups and before the
initiation of the program. Outcome measurements were recorded
1 day after the end of the program (POST 1), 1 month (POST 2),
3 months (POST 3), 6 months (POST 4), and 9 months (POST5)
after program termination.
Participants
Thirty-nine women aged 27 to 72 with a mean (SD) age of 56.65
(9.11) years, with CLBP participated in the study (see Table 1 for
description by group). Criteria for participation were duration of
low back pain for at least 6 months and generally good health.23
Exclusion criteria for participation to the program were spinal ste-
nosis, radiographic evidence of inammatory disease affecting the
spine, fracture, the presence of spondylolysis or spondylolisthesis,
important genetic structure abnormality in the spine, daily intensive
low back pain, pregnancy, and use of medication that might inu-
ence heart rate and/or blood pressure.23 All participants provided
informed consent before participation in the study while the study
has been approved by the university ethics committee.
Exercise Protocol
The treatment programs included 6 anterior-posterior exercises and
the duration of each exercise session was 60 minutes. Both exer-
cise programs were led by the same qualied exercise instructor
and started with a warm up lasting for 5 to 10 minutes, including
walking, stretching of low back muscles, and general stretching.
Cool-down exercises were part of each training session lasting 5 to
7 minutes, including walking at slow pace and stretching exercises.
Figure 1 — Participant owchart.
Stabilization Exercises and Low Back Pain 1297
Group A: Isometric Exercise Stabilization Group
The program consisted of isometric contractions without motion.
Exercise intensity increased through a progressively longer con-
traction time from week 1 to week 4. Contraction duration for the
rst week was 8 sec, for the second and third week was 10 sec
and for the fourth week was 12 sec. For example in the rst week,
participants performed isometric anterior pelvic tilt contractions
(8 sec), followed by relaxation (8 sec), isometric posterior pelvic
tilt contraction (8 sec) and relaxation (8 sec) for all exercises (see
Figure 2). There were 10 repetitions for each exercise.
Group B: Isotonic Exercise Stabilization Group
The program consisted of dynamic contractions of the same muscles
from similar starting exercise positions as those performed by the
isometric group. In all exercises, participants performed alternative
dynamic anterior (0.5 sec) and posterior (0.5 sec) pelvic tilt move-
ments without relaxation.18 Relaxation between sets was set at 10 sec
(Figure 2). For each exercise 1 set consisted of 10 repetitions and an
increase of exercise intensity was achieved by increasing the number
of sets performed. For the rst week, the numbers of sets were set at
5, for the second and third week at 6, and for the fourth week at 7.
Control Group
Participants did not take part in any form of organized exercise
except their daily life activities.
Testing Procedures
Data on HRQL and pain were collected via the Short Form-36v2
Health Survey (SF-36v2) in all measurement occasions. The SF-36v2
provides an index of self-perceived health status in 9 dimensions
of health.24 These are “physical functioning” with low scores
indicating signicant limitations in performing physical activities;
“role physical” with low scores indicating problems with work or
other activities as a result of physical problems; “bodily pain” with
low scores reecting high levels of pain that interfere with normal
activities; “general health” with low scores indicating evaluation of
general health as poor and possibility of getting worse; “vitality”
with low scores indicating feelings of tiredness and being worn out
and high scores reecting feeling full of energy most of the time;
“social functioning” with low scores indicating frequent interference
with normal social activities due to physical and emotional problems;
“role emotional” with low scores indicating problems with work or
other activities as a consequence of emotional problems; “mental
health” with low scores reecting frequent feelings of nervousness
and depression and high scores feelings of calm and happiness (all of
these subscales represent health domains); and the “reported health
transition” item. This is a general health rating item asking about
the amount of change in the participants’ health and can be analyzed
either as a categorical variable or as an ordinal variable or interval
scale.24 Lower scores indicate health much better than a year ago.
All items, scales, and summary measures are scored so that a higher
score indicates a better health state except the reported health transi-
tion that its response value is not scored as part of any SF-36v2 scale
or measure. There are 10 items to measure physical functioning, 4
items for role physical, 2 items for bodily pain, 5 items for general
health, 4 items for vitality, 2 items for social functioning, 3 items
for role emotional, 5 items for mental health, and 1 item to measure
reported health transition.24 No missing responses were observed.
This is due to the fact that the participants in the exercise groups
were residents of a small community where they were known to each
other. Hence, owing to social bonding between participants, all of
them were prompted by the other participants and the researchers
not to miss any exercise session.
Statistical Analysis
Initially, data normality was examined via consulting the ratios of
absolute skewness and kurtosis values to their respective standard
errors. Cronbach’s alpha values25 were also computed for each of
the SF-36v2 subscales and for all measurement occasions, except
reported health transition that consists of 1 item, to estimate internal
consistency reliability. Mauchly’s test of sphericity was used to
examine whether the variance of the changes in outcomes between
the different measurement occasions was constant. When indica-
tions existed that this was not the case, and a conventional F-test
would be biased, the Greenhouse-Geisser correction to the F-test
was employed to remove bias.
A one-way MANOVA using age and BMI as the dependent
variables was calculated to examine possible differences between
the 3 groups. Then, a one-way MANCOVA was computed on the
SF-36v2 dimensions data obtained in the rst measurement occasion
(PRE) to test for possible differences between the 3 groups on all 9
dependent variables using participants’ age and BMI as covariates. In
case of no differences between the groups on the rst measurement
occasion, a repeated measures MANCOVA (3 groups × 6 occasions)
including all 9 dependent variables with age and BMI as covariates
was computed to examine the multivariate interaction term between
groups (control, isometric stabilization, isotonic stabilization) and
time (PRE, POST 1, POST 2, POST 3, POST4, POST5).
Then, two-way analyses of variance (3 × 6) with repeated
measures on the second factor (time) followed, to examine the
interaction term for each one of the dependent variables, separately.
For the analysis of the signicant interaction term, pairwise mean
differences were determined using the Student Neuman-Keuls
multiple comparison procedure. The level of signicance was set
Table 1 Participant Characteristics (Mean ± Standard Deviation) by Study
Group
Characteristics Control Isometric Isotonic
Age (y) 62.92 ± 5.33 53.84 ± 11.37 53.18 ± 6.41
Height (cm) 1.57 ± 0.05 1.61 ± 0.05 1.60 ± 0.06
Body mass (kg) 70.66 ± 6.44 77.08 ± 14.61 73.10 ± 6.71
BMI (kg/m2) 28.63 ± 3.03 29.38 ± 5.15 28.52 ± 2.93
Note. One-way ANOVA and Student Neuman Keuls multiple comparison test indicated group differences for age.
Age and BMI have been included in the analyses of variance as covariates.
Abbreviations: BMI, body mass index.
1298 Moussouli et al
at P < .05. Percentage of improvement for each outcome measure
within each of the groups was also examined by estimating clinical
signicance values. These values indicate the percent of improve-
ment that corresponds to each time point separately, using scores
from the initial measurement as the reference point. In addition,
Cohen’s d effect size was calculated for each outcome measure
and time point within each of the groups separately, to provide a
further estimation of the magnitude of the change. The score of
the rst measurement was always used as the reference point for
the calculation. The d values indicating a “small,” “medium,” and
“large” effect size are .20, .50, and .80 respectively.26
Results
Skewness and kurtosis values supported data normality for the 9
subscale scores except for social functioning that exhibited a slight
deviation from normality (standardized skewness = 2.9, standardized
Figure 2 — Stabilization exercises used in the current study. Note. The exercises have been executed in an isotonic fashion for the 1 treatment group
and in an isometric fashion for the other treatment group.
Stabilization Exercises and Low Back Pain 1299
kurtosis = 2.6) and reported health transition with a slight deviation
for kurtosis (standardized kurtosis = 2.4). Further, all Cronbach’s
alpha values for all of the SF-36v2 subscales and for all 6 measure-
ment occasions were greater than .70 except for general health in
the rst occasion and social functioning in the fourth measurement
occasion, indicating generally high internal consistency for the
SF-36v2 subscales (Table 2). The present results for the assessment
of alpha values should be interpreted in the context of the limited
sample size.
The one-way MANOVA with a signicant multivariate effect
for group Wilks’s Lambda = .749, F (4, 70) = 2.72, P < .05, partial
eta squared = .13] showed that the groups did not differ signicantly
on BMI but they differed on age with the control group displaying
a greater mean age of approximately 62 yrs. compared with the 2
exercise groups with an average age of 53 yrs. (Table 1). The initial
one-way MANCOVA showed that there was not any multivariate
main effect for groups indicating that no differences existed in the
dependent variable means between the groups for the rst measure-
ment occasion (ie, PRE) [Wilks’s Lambda = .446, F (18, 52) = 1.43,
P > .05, partial eta squared = .33]. The 2-way MANCOVA (3 groups
× 6 measurement occasions) displayed a signicant multivariate
interaction effect [Wilks’s Lambda = .31, F (90, 1108.99) = 2.25,
P < .05, partial eta squared = .11].
Subsequent 2-way ANCOVAs showed signicant interaction
terms for physical functioning [F (8.30, 141.17) = 4.21, P < .05,
partial eta squared = .19], bodily pain [F (10, 170) = 2.92, P < .05,
partial eta squared = .14], general health [F (7, 170) = 7.33, P <
.05, partial eta squared = .30], vitality dimensions [F (10, 130.99)
= 3.91, P < .05, partial eta squared = .18], role emotional [F (10,
133.66) = 2.41, P < .05, partial eta squared = .12], mental health [F
(7.77, 132.20) = 5.48, P < .05, partial eta squared = 0.24], and related
health transition [F (10, 170) = 2.59, P < .05, partial eta squared
= .13]. No signicant interaction terms emerged for role physical
[F (10, 170) =1.73, P > .05, partial eta squared = .09], and social
functioning [F (10, 170) = 1.26, P > .05, partial eta squared = .06].
The Neuman-Keuls post hoc multiple comparison procedure with
the respective within error terms were used to analyze the statisti-
cally signicant interaction terms in the dependent variables above.
It was only for the SF-36v2dimensions of bodily pain (Table 3) and
vitality (Table 4) that signicant differences were found between
the PRE and POST1 measurements for the 2 treatment groups. For
some dependent variables a signicant mean decrease was found
in the control group indicating deterioration of HRQL. Therefore,
interpretation was focused on signicant differences between the
PRE and POST1 mean scores in the treatment groups that was the
case for bodily pain and vitality (Tables 3 and 4, respectively).
Details in relation to the remaining outcome variables are provided
as online supplementary material.
Group Differences
Direction of group mean differences is presented only for the
dependent variables of vitality and bodily pain for which analysis
of the signicant interaction terms was accompanied by signicant
mean differences between PRE and POST1 for the isometric group.
Group means for all dependent variables and all measurement occa-
sions together with percentage estimates of clinical importance
are presented in the respective tables as supplementary material.
Clinical importance estimates have been calculated for all groups
and measurement time points using the PRE measurement as the
reference point. Further, a measure of effect size (Cohen’s d) has
been calculated for all pairwise mean differences within each of
the 3 groups and for all dependent variables and measurement
occasions using always the PRE mean for the respective group, as
the reference point. The standard deviation of the PRE mean has
always been used in the calculation.
Bodily pain scores signicantly increased (ie, pain reduction)
from pre to post program participation for the isometric exercise
stabilization group only. A clinical importance change of 94% was
observed for the isometric stabilization group and an ES of 1.12
indicating a large difference (Table 3). No signicant differences
were observed between mean scores for the 2 other groups for any
measurement occasion. Further, no signicant differences emerged
between POST1 and subsequent measurement occasions for all
groups on bodily pain indicating maintenance of effects observed
after program termination for a period of 9 months.
Vitality scores increased signicantly from pre to post exer-
cise program participation, for the isometric exercise stabilization
group only, with a clinical importance increase of 76% and an ES
of .82 indicating a large mean difference (Table 4). No signicant
differences emerged within each of the other 2 groups. In addition,
no signicant mean differences emerged for any of the groups
Table 2 Cronbach’s Alpha Values for the Greek Version of SF-36v2 Subscales for All Measurement
Occasions
Measurement occasion
SF-36v2 subscales PRE POST1 POST2 POST3 POST4 POST5
1. Physical functioning 0.90 0.84 0.90 0.86 0.84 0.88
2. Role physical 0.88 0.91 0.95 0.91 0.91 0.91
3. Bodily pain 0.86 0.84 0.83 0.86 0.88 0.78
4. General health 0.60 0.87 0.89 0.78 0.78 0.82
5. Vitality 0.77 0.91 0.92 0.87 0.85 0.83
6. Social functioning 0.84 0.88 0.77 0.54 0.78 0.85
7. Role emotional 0.90 0.90 0.93 0.84 0.90 0.90
8. Mental health 0.84 0.91 0.92 0.89 0.92 0.75
9. Related health transition – – – – – –
Note. No values have been recorded for related health transition because it consists of 1 item.
Abbreviations: PRE, before training; POST 1, immediately after training; POST 2, 1 month follow-up; POST 3, 3-month follow-up; POST 4,
6-month follow-up; POST 5, 9-month follow-up.
1300
Table 3 Means, Standard Deviations, Estimates of Clinical Importance, and Effect Size for Bodily Pain
Testing
session Control (n = 13)
Clinical significance
Mean % ES Isotonic (n = 13)
Clinical significance
Mean % ES Isometric (n = 13)
Clinical significance
Mean % ES
PRE 68.38 ± 17.26 50.70 ± 19.70 49.30 ± 23.00
POST1 47.30 ± 32.99 –24.33 (–137.32, 88.66) 1.21 59.37 ± 18.43 31.92 (–92.81, 156.65) 0.44 75.21 ± 12.69 a,b 94.73 (–121.32, 310.78) 1.12
POST2 48.61 ± 30.98 –27.65 (–121.67, 66.37) 1.14 60.11 ± 19.02 43.14 (–150.8, 237.08) 0.47 64.88 ± 14.24 68.11 (–123.02, 259.24) 0.67
POST3 33.84 ± 13.86 –48.21 (–89.35,–7.07) 2.00 50.67 ± 12.56 14.83 (–90.50, 120.16) 0.15 64.51 ± 15.16 a67.11 (–114.77, 248.99) 0.66
POST4 47.45 ± 25.39 –29.68 (–95.96, 36.60) 1.21 50.29 ± 20.30 11.89 (–0.29, 132.07) 0.02 62.60 ± 17.52 60.29 (–110.70, 231.28) 0.57
POST5 40.00 ± 26.14 38.06 (–116.71, 40.59) 1.64 49.72 ± 6.51 12.31 (–81.78, 106.40) 0.05 65.11 ± 16.18 62.68 (–108.25, 233.61) 0.68
Note. Higher scores indicate reduced pain.
a Signicantly different from control.
b Signicantly different from pre.
Abbreviations: Abbreviations: PRE, before training; POST 1, immediately after training; POST 2, 1 month follow-up; POST 3, 3-month follow-up; POST 4, 6-month follow-up; POST 5, 9-month follow-up; ES, effect size (d).
Table 4 Means, Standard Deviations, Estimates of Clinical Importance, and Effect Size for Vitality
Testing
session Control (n = 13)
Clinical significance
Mean % ES Isotonic (n = 13)
Clinical significance
Mean % ES Isometric (n = 13)
Clinical significance
Mean % ES
PRE 66.34 ± 18.13 43.75 ± 18.57 50.48 ± 29.36
POST1 37.01 ± 29.36 –35.09 (–146.41, 76.23) 1.61 63.32 ± 19.07a79.84 (–140.18, 299.86) 1.11 74.72 ± 21.01a,b 76.69 (–176.46, 329.84) 0.82
POST2 40.38 ± 24.42 –35.15 (–121.31, 51.03) 1.43 60.86 ± 21.31 53.03 (–45.28, 151.34) 0.92 70.52 ± 18.09a55.08 (–27.25, 137.41) 0.68
POST3 34.13 ± 12.39 –45.26 (–87.79, –2.73) 1.77 59.09 ± 23.70a44.74 (–151.73, 241.21) 0.82 69.81 ± 19.49a69.06 (–188.5, 326.62) 0.65
POST4 48.32 ± 18.50 –22.69 (–93.68, 48.30) 0.99 60.16 ± 23.58 44.19 (–110.08, 198.46) 0.88 60.58 ± 20.09 41.16 (–127.59, 209.91) 0.34
POST5 42.40 ± 18.43 –32.33 (–91.84, 27.21) 1.32 54.00 ± 25.88 43.23 (–116.17, 202.63) 0.55 56.67 ± 21.51 33.65 (–145.45, 212.75) 0.21
Note. Higher scores indicate reduced pain.
a Signicantly different from control.
b Signicantly different from pre.
Abbreviations: Abbreviations: PRE, before training; POST 1, immediately after training; POST 2, 1 month follow-up; POST 3, 3-month follow-up; POST 4, 6-month follow-up; POST 5, 9-month follow-up; ES, effect size (d).
Stabilization Exercises and Low Back Pain 1301
between the POST1 and subsequent measurement occasions indicat-
ing maintenance of program effects for a period of 9 months after
program termination.
Discussion
The aim of the current study was to compare the effectiveness of
isometric and isotonic stabilization exercises in reducing pain and
enhancing HRQL in a sample of women with CLBP. In general,
only a few randomized clinical trials have been conducted to exam-
ine the effectiveness of stabilization exercises and these studies
have shown indications of long-lasting benets in the treatment of
low back pain.1,9,10,12 The present results extend previous ndings
demonstrating that stabilization exercises are effective not only in
improving functional ability but also HRQL parameters in patients
with CLBP. The results supported the superiority of an intensive
4-week isometric exercise stabilization program in comparison
either to an isotonic exercise stabilization program or to no exer-
cise at all, in reducing levels of bodily pain and improving levels
of vitality in a sample of women with CLBP. The ndings showed
statistically signicant and clinically important changes of a large
magnitude in relation to the improvement of vitality and bodily pain
levels. Further, the exercise effects were maintained for a period
of 9 months after termination of the exercise program, further sup-
porting the long-lasting benets of such a program.
The ndings are in agreement with previous studies document-
ing positive effects on functionality of patients with CLBP which
suggests that interventions consisting of lumbar stabilization exer-
cises are particularly effective for managing CLBP.9,19,22 System-
atic reviews1,9,10,12 have concluded that stabilization exercises can
reduce pain and disability in patients with CLBP but with effects
not really greater when compared with active treatment control
groups. A related study19 demonstrated that both an isometric and
an isotonic PNF program led to a greater reduction in low back
pain. Other ndings have supported the effectiveness of rhythmic
stabilization exercises when compared with either transcutaneous
electrical stimulation or a combination of strength and exibility
exercise program20,27 in improving functional measures and reducing
disability. In the same fashion, it has been shown that a 3-month
lumbar stabilization exercise program based on the abdominal
drawing-in-maneuver and prone kneeling had positive effects on
chronic low back pain and quality of life patients with CLBP.22 It
should be noted, however, that some studies reported that stabili-
zation exercises do not add any more benets to standard physio-
therapy programs.13,14 Comparison of these results with the present
ndings is difcult as we did not examine stabilization exercises in
combination with other treatment therapies.
Studies examining the effects of stabilization exercise on aspects
of HRQL in patients with CLBP have been sparse.12 The present nd-
ings add new insights on the specics of using stabilization exercises
in improving dimensions of HRQL. First, our results showed that
stabilization exercises improve HRQL which is in agreement with
previous ndings. Particularly, improvements in HRQL were seen
after a 3-month lumbar stabilization exercise program,22 a combined
treatment including stabilization exercises21 and a conventional
physical therapy program with additional stabilization exercises.14
Although it is not clear whether stabilization exercises improve
HRQL more than other types of exercise,28 these results favor the
use of such exercises for enhancing HRQL in patients with CLBP.
In addition the present results indicated that the gradual increase
of duration of muscle contraction used in the isometric stabilization
program rather than the gradual increase of the number of repetition
sets used in the isotonic stabilization program was more effective
in reducing bodily pain and increasing levels of vitality. However,
the possible mechanism for such an effect to occur is still unclear.
Research has shown that both types of exercise programs signi-
cantly increased lumbar spinal range of motion and spinal muscular
endurance in women with CLBP.19 Moreover, the greatest reduction
in back pain was observed immediately after exercise for the iso-
tonic program but dimensions of HRQL have not been examined.
Furthermore, research has examined isometric and isotonic exercises
based on the principles of PNF, which are performed against manual
resistance provided by a therapist.19 This differs from the present
program as external resistance was limited to the body weight of
the participants. Nevertheless, the isometric stabilization exercises
applied in the current study involve several muscle groups, activated
around the trunk, the pelvis, and the hips (Figure 2). Since these
exercises are based on cocontraction of antagonistic muscle groups
to maintain trunk and whole body position, we can assume that this
technique improved signicantly static strength of the associated
musculature and perhaps muscle co-ordination. Trunk stabilization
is a necessary requirement for performing several everyday tasks
such as rising from a chair or carrying an object. In these move-
ments, the trunk muscles work almost in an isometric fashion to
maintain trunk integrity. This might explain why the isometric
exercise program resulted in greater improvement in the pain and
vitality dimensions of HRQL measures compared with the other 2
groups. In contrast, isotonic exercises involve dynamic contractions
and they can result in increases in range of motion and strength.
Consequently, it could be suggested that improvements of dynamic
trunk movement performance in patients with CLBP did not impact
aspects of HRQL to the same extent as isometric adaptations did.
It is also noteworthy that these results were the outcome of a
short term (4-weeks) but intense (4 sessions of 60 min per week)
isometric exercise program in comparison with longer exercise
programs usually studied. Moreover, the effectiveness of the iso-
metric stabilization program is further substantiated by the length of
period that the benets obtained from the program are maintained.
Thus, the analogy of program length to the magnitude of the ben-
ets obtained and the duration for which benets are maintained,
provides grounds for more systematic research work in this area.
The present ndings advance the study of stabilization exercises in
a search of methods for improving HRQL in women with CLBP
and opens new research avenues for further investigations examin-
ing the effects of such an exercise program on other functional and
disability-related outcomes.
The present work adds to the literature of the study of physi-
cal exercise methods to counteract the problem of low back pain
and extends ndings to the psychosocial domain of HRQL. Bodily
pain as operationalized via the SF-36v2 instrument measures the
intensity of bodily pain or discomfort experienced by the patient
and the functional impact of pain from the aspect of interference
with individuals’ normal activities.24 The present ndings indicate
that isometric stabilization exercises appear more benecial in
reducing the intensity of bodily pain and discomfort experienced by
the patient compared with either isotonic exercises or no exercise
at all. Vitality is operationalized as the extent to which the patients
feel as having energy available to the self in contrast to feeling
tired and worn out.24 The present ndings showed that isometric
stabilization exercises led to increased levels of feeling energetic
rather than feeling tired and worn out, thus, contributing to more
positive feelings during everyday life. Indeed, it has been shown
that there is a positive relationship between self-rated health and
happiness among community dwelling older adults.29
1302 Moussouli et al
In relation to the HRQL dimensions where no signicant effects
were found, an observation of the results may reveal that while a
deterioration of scores was found for the control group over time,
positive effects were observed for the remaining dimensions, albeit
nonsignicant. Observation of the clinical signicance estimates
reveals trends of positive effects for both exercise programs on all
dimensions of HRQL with greater effects observed for the isometric
exercise group. However, nonsignicance for these effects may be
attributed both to the small number of participants within each group
corresponding to lowered statistical power combined with a weaker
effect of the interventions for these particular dimensions. Future
research in this area should be conducted with a greater number of
participants per group to achieve enhanced levels of statistical power.
The present results are limited mainly to middle age women
characterized by chronic low back pain, thus restricting external
validity of the ndings. Future studies aiming to further understand-
ing of the effects of an intense program of stabilization exercise on
HRQL among individuals with CLBP may employ either women of
an older age or men. Despite that random allocation of the women
to the 3 groups was not feasible (random allocation took place
only between the 2 exercise groups), similarity of the 3 groups
in their demographic characteristics provide some support to the
equivalence of the groups before initiation of the intervention. For
instance, given that the 2 communities belong to the same county,
habits and values of people generally coincide. Further, no selection
bias is believed to have been introduced to the study given that the
control group women did not select not to participate; rather the
technical difculty of the traveling distance was the main reason
for non participation, a reason unrelated either to the variables of
the study or the requirements of the study design. Therefore, we
believe that the lack of randomization had only minimal impact on
the ndings. In addition, control group women, had initially agreed
to participate in an exercise program dealing with their back pain.
However, such a program would be delivered after the 2 experi-
mental exercise groups had concluded their program in order for
the control group to function as such.
The present ndings expand the evidence base of methods for
enhancing HRQL in patients with CLBP. It is shown that the ben-
ets from the use of isometric stabilization physical exercise can
extend to individuals’ everyday life by enhancing levels of vitality
and subjective energy for everyday activities, contributing to a more
balanced and happier life. Clearly, maintaining a health-related
quality of life is important given the centrality of this concept in
the domain of chronic care.2
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