Authors: Pedro A´ngel Baena-Beato, PhD Manuel Delgado-Ferna´ndez, PhD Enrique G. Artero, PhD Alejandro Robles-Fuentes, PhD Marı´a Claudia Gatto-Cardia, BSc Manuel Arroyo-Morales, PhD
BRIEF REPORT
Affiliations: From the Department of Physical Education and Sport, University of Granada, Granada, Spain (PA´B-B, MD-F, AR-F); Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia (EGA); Department of Education, University of Almerı´a, Almerı´a, Spain (EGA); Department of Physiotherapy, Universidade Federal da Paraı´ba, Paraı´ba, Brasil (MCG-C); and Department of Physiotherapy, University of Granada, Granada, Spain (MA-M).
Correspondence: All correspondence and requests for reprints should be addressed to Manuel Delgado-Ferna´ndez, PhD, Departamento de Educacio´n Fı´sica y Deportiva, Facultad de Ciencias de la Actividad Fı´sica y el Deporte Universidad de Granada, Carretera de Alfacar, s/n, 18011, Granada, Spain.
Disclosures: Supported by a postdoctoral fellowship from the Spanish Ministry of Education (EX-2010-1008). Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/14/9307-0615 American Journal of Physical Medicine & Rehabilitation Copyright * 2014 by Lippincott Williams & Wilkins DOI: 10.1097/PHM.0000000000000123
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Exercise
Disability Predictors in Chronic Low Back Pain After Aquatic Exercise ABSTRACT Baena-Beato PA´, Delgado-Ferna´ndez M, Artero EG, Robles-Fuentes A, GattoCardia MC, Arroyo-Morales M: Disability predictors in chronic low back pain after aquatic exercise. Am J Phys Med Rehabil 2014;93:615Y623. The physical and psychological factors associated with reduction of disability after aquatic exercise are not well understood. Sixty participants (30 men and 30 women; age, 50.60 [9.69] yrs; body mass index, 27.21 [5.20] kg/m2) with chronic low back pain were prospectively recruited. The 8-wk aquatic therapy program was carried out in an indoor pool sized 25 6 m, with 140-cm water depth and 30-C (1-C) of water temperature, where patients exercised for 2Y5 days a week. Each aquatic exercise session lasted 55Y60 mins (10 mins of warm-up, 20Y25 mins of aerobic exercise, 15Y20 mins of resistance exercise, and 10 mins of cooldown). Demographic information, disability (Oswestry Disability Index), back pain (visual analog scale), quality-of-life (Short Form 36), abdominal muscular endurance (curl-up), handgrip strength, trunk flexion and hamstring length (sit and reach), resting heart rate, and body mass index were outcomes variables. Significant correlations between change in disability and visual analog scale (at rest, flexion, and extension), curl-up and handgrip (r ranged between j0.353 and 0.582, all Ps G 0.01) were found. Changes in pain and abdominal muscular endurance were significant predictors of change in disability after therapy. Key Words:
Disability, Chronic Low Back Pain, Muscle Endurance, Aquatic Exercise
D
isability is a complex concept covering impairments, activity limitations, and participation restrictions, reflecting the interaction between features of a person’s body and features of the society in which he/she lives.1 Patients with chronic low back pain (CLBP) experience clinical manifestations, including physical and psychological symptoms that affect their health status.2 Most low back painYrelated costs to society derive from patients’ disability, which is also the main determinant of patients’ quality-of-life (QoL).3,4 Disabilities are common in patients with CLBP,5 which is the third leading cause of chronic functional disability after respiratory conditions and injuries.6 Therefore, treating disability is as important as treating pain.7 Different therapeutic exercise programs have showed effectiveness to improve disability,8Y10 but the results are controversial.11 The factors interacting with physical measures of impairment in explaining disability and the relative Change in Disability After Aquatic Exercise
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extents to which psychological and physical factors account for improvements in outcome after therapy for CLBP have rarely been examined. Mannion et al.12 established explicative models of changes in disability promoted by therapeutic exercise, where changes in pain, psychological distress, and fearavoidance beliefs accounted for only 24% of the changes in disability after therapy. More precise and explicative models are needed to treat adequately this health problem. Disability in back pain is highly influenced by pain, physical impairment, and psychological and psychosocial factors.3,13 Patients with CLBP usually report that pain is their main problem and the main cause of their disability.3 In individuals with chronic disabilities, pain may induce serious psychological problems, negatively affecting QoL,14 where psychological distress has been identified as one potential pathway by which an episode of pain influences the development of persistent disabling symptoms.15 These factors explain only a portion of how CLBP affects disability, and other factors should be explored. There are evidences that exercise can decrease disability, pain, and secondary physical deconditioning in patients with CLBP,16 where physical treatments are based on the assumption that increased muscle strength, aerobic capacity, and stretching are crucial for the resumption of activities and for the reduction of disability.17,18 Previous studies have concluded that aquatic exercise may contribute to a decline in disability and pain and produce improved psychological and psychosocial factors.8,9 Aquatic exercise is of particular interest in CLBP because the unique properties of water reduce stress in joints and decrease axial loading of the spine.19 Moreover, continuous limb movements against the water resistance result in muscle strength20 and cardiovascular benefits.21 The aquatic environment enables the participant to perform movements that are normally difficult or impossible on land.22 Several studies indicate that therapeutic aquatic exercise can be a safe and effective treatment modality for patients with CLBP.9,10 There are no previous models to explain the clinical and physical factors involved in disability improvements after aquatic exercise programs in CLBP. To the best of the authors’ knowledge, no previous study has investigated the association between pain, QoL, and health-related fitness with disability in patients with CLBP after therapy. The aim of the study was to discover potential predictors of improvement disability in CLBP treated with aquatic exercise.
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METHODS Participants A total of 60 sedentary adults with CLBP (30 men and 30 women), defined as arising below the last rib margin and above the inferior gluteus lines and with a duration pain of greater than 12 wks, aged 50.60 (9.69) yrs, with body mass index (BMI) of 27.21 (5.20) kg/m2, volunteered to participate in this study. Participants were recruited in Massam Sport Center (Granada, Spain), and they received written and oral instructions about the intervention, the test protocol, and the possible risks and benefits of the study. Written informed consent was obtained before participation. The study was approved by the ethical committee of the University of Granada and was performed in accordance with the Helsinki Declaration, last modified in 2000. The inclusion and exclusion criteria for this study appear on Table 1. The study flow of participants is presented in Figure 1.
Treatment The 8-wk aquatic therapy program was carried out in an indoor pool sized 25 6 m, with 140-cm water depth, 30-C (1-C) of water temperature, where participants exercised for 2Y5 days a week. Each aquatic exercise session was conducted in small groups of 8 participants and lasted 55Y60 mins (10 mins of warm-up, 20Y25 mins of aerobic exercise, 15Y20 mins of resistance exercise, and 10 mins of cooldown). The resistance exercises progressed throughout the program by changing the number of repetitions per set (volume, 3 sets per 12 repetitions
TABLE 1 Inclusion and exclusion criteria Inclusion criteria: -Age between 25 and 64 yrs -Presence of self-reported low back pain for more than 12 wks23 Exclusion criteria: -Symptoms or signs that might suggest serious medical illness -Pregnancy or recent childbirth -Major rheumatologic, neurologic, neoplastic, or other conditions that may prevent full participation in the intervention -Previous spinal surgery, inflammatory, infectious, or malignant diseases of the vertebra -Presence of any psychiatric disorder that might affect the compliance and the assessment of symptoms -Presence of severe cardiovascular disease -Engagement in physical activity for 60 mins or longer per week during the last 12 mos24
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FIGURE 1 Flow of participants throughout the trial.
in the first week to 3 sets per 15 repetitions in the eighth week), by including specific resistance materials that increase the resistance offered by the water, and by increasing the velocity of the movements. Noodles and cuff devices were used for upper-body and lower-body exercises, respectively. Each training session included the following resistance exercises: hip flexion-extension, hip abduction-adduction, arms abduction-adduction at chest level, curl-ups, scissors leg, and backstroke kick with water noodle under the waist. The planning of the aerobic exercises was increased considering the intensity (Borg scale of 6Y20, 10Y12 in the first week to 12Y15 in the eighth week) and the volume (minutes). The aerobic exercises incorporated large muscle mass and consisted of lateral displacements, long-lever pendulumlike movements of the extremities, forward and backward jogging with arms pushing, pulling and pressing, leaps, kicks, leg crossovers and hopping movements focusing on traveling in multiple directions, and bounding off the bottom of the pool. Heart rate was assessed using the POLAR 610 heart-rate monitor (Polar Electro OY, Finland) at different moments of the program when patients were out of the pool. Participants were monitored in different sessions to assess if the intensity recommendations were followed. At the end of each session, static stretching www.ajpmr.com
techniques were performed for gluteus, lumbar back, and hamstrings, as part of the cooldown. Sessions were supervised by physical therapists with more than 6 yrs of experience in the management of CLBP through aquatic exercise programs.
Outcome Measures To assess changes in different parameters after aquatic exercise, all measurements were taken at baseline and 24 hrs after discharge in the aquatic exercise program.
Questionnaires Participants were evaluated for the following self-completed questionnaires.
Oswestry Low Back Pain Disability Questionnaire The Spanish version of the Oswestry low back pain disability questionnaire26 was used. The reliability and validity of this questionnaire have been found to be acceptable,26 and the minimal clinical change is considered to be 10%.27
Visual Analog Scale Back pain was assessed at rest and during movement of the trunk (flexion and extension) using a Change in Disability After Aquatic Exercise
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visual analog scale (VAS). The reliability and validity of VAS have been found to be acceptable,28 and the minimal clinical change is considered to be 15 mm.29
Short Form 36 Health Survey The Spanish version of Short Form 36 (SF-36) is a generic instrument assessing health-related QoL.29 It contains 36 items and yields 8 domains (parameters). These 8 parameters can be used to derive 2 composite scoring summaries: physical composite summary (PCS SF-36, physical functioning, physical role, bodily pain, and general health perceptions) and mental composite summary (MCS SF-36, vitality, social functioning, mental health, and emotional role). The SF-36 is a sensitive measure of treatment success in patients with low back pain.30 Each domain is scored on a scale from 0 (worst possible health) to 100 (best possible health).31
Fitness Outcomes Participants were evaluated in fitness for curl-up test, handgrip strength, sit and reach test, and resting heart rate. BMI was also measured. All testing sessions were conducted by the same experimented researcher.
Curl-up Test Abdominal muscular endurance was measured using the curl-up test.25 The cadence for the test was 40 beats/min, paced by a metronome. The test was terminated when the subject was unable to maintain the required cadence or unable to maintain the proper curl-up technique for 2 consecutive repetitions despite feedback from the researcher. The highest number of repetitions completed while maintaining proper form was recorded.
Handgrip Strength Test A hand dynamometer with adjustable grip was used (TKK 5101 Grip D; Takey, Tokyo, Japan). The test was performed twice, and the maximum score for each hand was recorded in kilograms. Optimal grip was noted for each participant in the pretest and repeated in the posttest. The sum of the scores achieved by the left and right hands was used in the analysis.32
Sit and Reach Test Trunk flexion and hamstring length were determined via the sit and reach test, as described by the American College of Sport Medicine’s protocol.25
Resting Heart Rate Participants were instructed in the procedure of measuring their pulse rate and then were asked
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to register resting heart rate manually at home, from the carotid artery using a stopwatch. They registered resting heart rate in four nonconsecutive days during pretest and posttest weeks. The mean heart rate among the four measurements was used as resting heart rate before and after the intervention.
Body Mass Index Weight (kilograms) was measured using Octapolar bioimpedance analyses (Biospace Inbody 720; Biospace Company, Ltd, Seoul, Korea). Biospace Inbody Analyse has been found to be reliable.33 Height (meters) was measured in the Frankfurt plane with a telescopic height-measuring instrument (Type SECA 225; range, 60Y200 cm; precision, 1 mm). BMI was calculated (kg/m2).
Statistical Analyses Mean and 95% confidence interval were reported for continuous variables with a normal distribution. Normal distribution of data was checked using Kolmogorov-Smirnov test. A t paired test was carried out to show the difference between baseline and postintervention data. Pearson and Spearman correlation analyses were applied whenever appropriate. The correlation analyses were carried out between the change (,), postdifference-predifference at baseline (pretest) and follow-up (posttest), in the disability (Oswestry Disability Index, ODI), back pain (VAS at rest), PCS SF-36 and MCS SF-36, abdominal muscular endurance (curl-up), handgrip strength, trunk flexion and hamstring length (sit and reach), resting heart rate, and BMI, after the physical therapy program. The assumptions of normality, linearity, and homoscedasticity were investigated by the residual scatterplots. Stepwise multiple regression analysis was used to explore which variables could explain the variation in disability (dependent variable). The changes in back pain, health-related QoL, abdominal muscular endurance, handgrip strength, trunk flexion and hamstring length, resting heart rate, and BMI were considered independent variables. The requirements of an independent variable to be included in the multiple regression analysis were as follows: (1) the correlation coefficients between the dependent variable and the independent variables were significant and r Q 0.25, and (2) the correlation coefficients between the independent variables were r e 0.7.34 Finally, the final model was validated using bootstrapping. Specifically, the bootstrapping method was carried out with repeated samples of the same size as the original samples in replacement. Two thousand replications were produced to estimate bootstrap bias-corrected and accelerated
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confidence intervals. For statistical analyses, significance level was set at P G 0.05. All analyses were performed using R software (2.9.3).
RESULTS Forty-one percent of the participants had an educational status of unfinished studies and primary school, and 59% had secondary school and a university degree; 75% of the participants listed civil status as married. Occupational status was distributed as housewife, 23%; working, 42%; retired, 22%; and unemployed, 13%. All participants were white from Granada metropolitan area. Participants showed moderate disability (mean [SD], 29.3 [13.4]),35 pain was from moderate to intense (mean [SD], 6.20 [2.23]),36 PCS SF-36 was low (mean [SD], 35.9 [9.89]),31 MCS SF-36 was moderate (mean [SD], 50.2 [11.4]),31 curl-up was low (mean [SD], 12.4 [5.41]),25 handgrip test was from low to moderate (mean [SD], 69.4 [20.2]),37 and sit and reach test was very low (mean [SD], 9.15 [9.86]),25 with BMI of overweight (mean [SD], 27.2 [5. 20])25 and resting heart rate (mean [SD], 69.4 [8.88]).38 Table 2 shows the baseline and postintervention scores.
Correlational Analyses Significant positive correlations between change in disability and VAS at rest (r = 0.582, P G 0.01), VAS at flexion (r = 0.410, P G 0.01), and VAS at extension (r = 0.424, P G 0.01) were moderate. Significant negative correlations were also found between change in disability and change in curl-up (r = j0.353, P G 0.01), and change in disability and change in handgrip strength (r = j0.431, P G 0.01) were moderate.
In addition, significant correlations existed among the independent variables (j0.353 G r G 0.582; see Table 3), but none was considered to be multicollinear (defined as r 9 0.70); therefore, each one was included in the regression analyses.
Regression Analyses Stepwise regression analyses revealed that changes in back pain intensity and abdominal muscular endurance were independent and significant predictors of change in disability after aquatic exercise, and when combined, they explained 48% of the variance (see Table 4).
DISCUSSION Current findings suggest that changes in back pain intensity and abdominal muscular endurance after 8 wks of aquatic exercise program have a relevant contribution to changes in CLBP-related disability. Disability related to CLBP may be caused by pain, physical impairment, psychological distress, and psychosocial factors.3,39 This study is the first to specifically examine disability determinants related to pain intensity and abdominal muscular endurance, after a treatment based on aquatic exercise program. Because rehabilitation strategies are focused on reducing pain and clinical repercussions from CLBP, particularly disability, understanding potential determinants for reduced disability may assist in the rehabilitation process in these patients. We observed that ODI and back pain (VAS) decreased in the participants beyond the minimal clinical change accepted in patients with low back pain,27 where they improved their levels from baseline
TABLE 2 Effects of an 8-wk aquatic therapy program in adults with CLBP Pretest, Posttest, Mean T SEM Mean T SEM ODI, scores of 0Y100
29.3 T 13.4
VAS rest, cm, 0Y10 VAS flex, cm, 0Y10 VAS ext, cm, 0Y10 PCS SF-36, scores of 0Y100
6.20 T 6.30 T 5.18 T 35.9 T
2.23 2.32 3.05 9.89
MCS SF-36, scores of 0Y100 Curl-up, no. repetitions HS, kg SR, cm HRR, ppm BMI, kg/m2
50.2 T 12.4 T 69.4 T 9.15 T 69.4 T 27.2 T
11.4 5.41 20.2 9.86 8.88 5.20
P
Minimum and Maximum Values in Healthy Adults
16.8 T 11.3 G0.0001 Minimal functional limitation G 20 to maximal functional limitation 9 8035 2.65 T 2.11 G0.0001 Mild to moderate pain G 4 to severe 9 636 2.43 T 2.14 G0.0001 1.85 T 2.15 G0.0001 44.9 T 9.08 G0.0001 Lowest possible score of 0 to highest possible score of 10031 50.1 T 9.56 0.932 20.8 T 5.83 G0.0001 Need improvement, 5, to excellent, 2525 75.1 T 20.5 G0.0001 Very poor, e59, to excellent, 910737 13.5 T 9.54 G0.0001 Need improvement, 17, to excellent, 3525 64.8 T 7.78 G0.0001 Bradycardia (G40Y45), tachycardia (990Y95)38 26.8 T 5.01 G0.0001 Normal, 18.5Y24.9, to overweight, 25.0Y29.925
HRR, heart rate at rest; HS, handgrip strength; SR, sit and reach; VAS ext, VAS at extension; VAS flex, VAS at flexion; VAS rest, VAS at rest.
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TABLE 3 Pearson product-moment correlation matrix for study variable , ODI , , , , , , , , , ,
ODI PCS SF-36 VAS rest VAS flex VAS ext HS SR BMI HRR curl
1.00 j0.009 0.582a 0.410a 0.424a j0.431a j0.193 0.058 0.242 j0.353a
, PCS SF-36
, VAS rest
, VAS flex
, VAS ext
, HS
, SR
, BMI
, HRR , Curl
V V V V V V V V 1.00 V V V V V V V j0.164 1.00 V V V V V V j0.446a 0.625a 1.00 V V V V V j0.076 0.655a 0.570a 1.00 V V V V b a 0.314 j0.355 j0.373a j0.385a 1.00 V V V 0.215 j0.141 j0.221a j0.015 0.348a 1.00 V V 0.114 0.244 0.072 0.199 0.095 j0.125 1.00 V j0.018 0.223 0.305b 0.150 j0.481a j0.176 j0.098 1.00 b 0.023 j0.039 j0.314 j0.153 0.288b 0.206 0.182 j0.349a
V V V V V V V V V 1.00
a
P G 0.01. bP G 0.05. ,, change between postdifference-predifference at baseline (pretest) and follow-up (posttest); HRR, heart rate at rest; HS, handgrip strength; SR, sit and reach; VAS ext, VAS at extension; VAS flex, VAS at flexion; VAS rest, VAS at rest.
in 43% in ODI, 57% in VAS at rest, 61% in VAS in flexion, and 64% in VAS in extension. The authors also observed an increase of 20% in the physical domains of health-related QoL (PCS SF36), and MCS SF36 showed a very slight decrease of less than 1%, but the differences before and after the intervention were not statistically significant (see Table 2). These changes were accompanied by improvements in fitness and BMI, where participants obtained improvements of 68% in the curl-up test (moved from low to good level),25 8% in the handgrip test (moved from low to medium level), 47% in the sit and reach test,25 6.6% in the heart rate at rest,38 and 2% in BMI keeping in overweight.25 To the best of the authors’ knowledge, only one study has investigated predictor’s variables in disability after therapy in patients with CLBP.12 Mannion et al.12 (2001) also reported a model where pain, psychological distress, and fear-avoidance belief accounted for 24% of the variance in disability after treatment. The study’s model was able to explain in total 48% of the variability in disability after therapy in patients with CLBP, where a reduction of pain intensity combined with an improvement in abdominal muscular endurance could contribute to reducing disability. Patients with CLBP usually report that pain is their main problem and the main cause of their disability.3 In the present study, change in pain is the variable with the largest contribution (33%) to the total explained variance; this was reflected by higher back pain intensity in patients with CLBP reporting greater disability. These results are in accordance with previous studies using multivariate analysis to predict disability, which have shown that pain normally explains the greatest or second
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greatest proportion of the variance.12,13,40,41 The relationship between disability and pain is bidirectional and a complex process, as disability is a symptom of pain resulting in loss of function. Back pain may lead to disability through its effects on physical impairment42 and psychological distress.15 It is often assumed that patients who feel more disabled and thus report more daily life restrictions caused by pain intensity43 will be those who are less physically active in CLBP.44 This is reflected in treatments recommended for CLBP, which typically promote increased physical activity to aid recovery and reduce pain intensity and disability. Abdominal muscle endurance was a significant and relative new determinant of disability in the present study (15% to the total explained variance in disability after therapy) and was one of the few physical factors that retained its importance when considered in combination with the pain. One important risk factor for low back pain is weakness of abdominal muscles,45,46 and strengthening of these is often associated with significant improvements of CLBP as well as with decreased functional disability.47Y49 Abdominal muscular endurance is suggested to be reduced in patients with CLBP,50 because weakened abdominal muscles cannot maintain normal inclination of the pelvis, which increases lordosis of the lumbar spine,51 and an increase of lumbar lordosis has shown to be inversely correlated with pain.52 Changes in muscle activity have been observed in experimental53 and clinical studies54 induced by pain, where reflex inhibition is suggested to play a role.55 The role of muscular strength in the performance of activities of daily living (sitting, standing, lifting, or rolling over in bed), as well as in the prevention of chronic disease, is increasingly
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A, regression coefficient; ,, change between postdifference-predifference at baseline (pretest) and follow-up (posttest); r 2, variability of disability explained by the respective predictor in percent; VAS rest, VAS at rest.
32.7 15.3 0.190 G0.0001 G0.0001 1.326 6.241 j3.939 3.335 2.256 j0.935 j1.141 to 7.850 1.596Y2.945 j1.413 to j0.552 Interceptil , VAS rest , curl
3.359 2.263 j0.937
j1.712 to 8.430 1.537Y2.989 j1.414 to j0.461
0.597 j0.376
r2 (%) P t Standardized Coefficients, A Bootstrap, A Bootstrap BCA, 95% CI 95% CI for A Unstandardized Coefficients, A Independent Variables
TABLE 4 Summary of stepwise regression analyses to determine predictors of improvement in disability (r 2 = 48%)
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being recognized.56,57 There is an association between abdominal muscle endurance and disability, where qualitative changes in posture58 and movement can occur dramatically and spontaneously because of gradual changes in parameters of abdominal muscular endurance, resulting in some degree of disability hindering the patient to perform activities of daily living.59 The authors recognize some limitations of the study. They included a relatively small sample size (n = 60). However, because of the small sample size, the number of independent variables entered in the regression analysis was limited to reduce the likelihood of a type II error. Other relevant outcomes such as lumbar musculature endurance levels should be examined in future research to provide more global information about the relationship between physical condition and disability. Long-term outcomes were not performed in these subjects so it cannot be determined whether the effect of the treatment can be maintained over time. Another limitation may be that group interaction or attention from the therapist gave positive feeling to the participants.
CONCLUSIONS Changes in pain intensity and abdominal muscular endurance were significant predictors of change in disability in patients with CLBP after therapy. Aquatic exercise decreases levels of disability and back pain, increases QoL, and improves BMI and fitness in sedentary adults with CLBP. Therapists working with patients with CLBP should take into account these relationships to improve the management of CLBP-related disability. ACKNOWLEDGMENTS
The authors thank the Massam Sport Center (Granada, Spain) for allowing them to use the facilities and all the participants for their collaboration. REFERENCES 1. World Health Organization: United Nations Educational, Scientific and Cultural Organization, International Labour Organization, International Disability and Development Consortium. Community-based rehabilitation: CBR guidelines. Geneva, Switzerland, World Health Organization, 2010 2. Koes B, van Tulder M, Lin C, et al: An updated overview of clinical guidelines for the management of nonspecific low back pain in primary care. Eur Spine J 2010;19:2075Y94 3. Kovacs FM, Abraira V, Zamora J, et al: Correlation between pain, disability and quality of life in patients with common low back pain. Spine 2004;29:206Y10
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4. Kovacs FM, Abraira V, Zamora J, et al: The transition from acute to subacute chronic low back pain: A study based on determinants of quality of life and prediction of chronic disability. Spine 2005;30:1786Y92 5. Coste J, Paolaggi JB, Spira A: Classification of nonspecific low back pain: I. Psychological involvement in low back pain. A clinical, descriptive approach. Spine 1992;17:1028Y37 6. Walker BF: The prevalence of low back pain: A systematic review of the literature from 1966 to 1998. J Spinal Disord 2000;13:205Y17 7. Kovacs F, Muriel A, Castillo-Sa´nchez MD, et al: Fear avoidance beliefs influence duration of sick leave in Spanish low back pain patients. Spine 2007;32:1761Y6 8. Cuesta-Vargas AI, Garcı´a-Romero JC, Arroyo-Morales M, et al: Exercise, manual therapy, and education with or without high-intensity deep-water running for nonspecific chronic low back pain: A pragmatic randomized controlled trial. Am J Phys Med Rehabil 2011;90:526Y34 9. Baena-Beato PA, Arroyo-Morales M, Delgado-Ferna´ndez M, et al: Effects of different frequencies (2Y3 days/week) of aquatic therapy program in adults with chronic low back pain. A non-randomized comparison trial. Pain Med 2013;14:145Y58 10. Dundar U, Solak O, Yigit I, et al: Clinical effectiveness of aquatic exercise to treat chronic low back pain. Spine 2009;34:1436Y40 11. Le Fort SM, Hannah E: Return to work following an aquafitness and muscle strengthening program for the low back injured. Arch Phys Med Rehabil 1994; 75:1247Y55 12. Mannion AF, Junge A, Taimela S, et al: Active therapy for chronic low back pain part 3. Factors influencing self-rated disability and its change following therapy. Spine 2001;26:920Y9 13. Koho P, Aho S, Watson P, et al: Assessment of chronic pain behaviour: Reliability of the method and its relationship with perceived disability, physical impairment and function. J Rehab Med 2001;33:128Y32 14. Tarsuslu T, Yu¨min ET, Oztu¨rk A, et al: The relation between health-related quality of life and pain, depression, anxiety, and functional independence in persons with chronic physical disability. Agri 2010;22:30Y6 15. Pincus T, Vogel S, Burton AK, et al: Fear avoidance and prognosis in back pain-a systematic review and synthesis of current evidence. Arthritis Rheum 2006; 54:3999Y4010 16. Rainville J, Hartigan C, Martinez E, et al: Exercise as a treatment for chronic low back pain. Spine J 2004; 4:106Y15 17. Verbunt JA, Seelen HA, Vlaeyen JWS, et al: Disuse and deconditioning in chronic low back pain: Concepts and hypothesis on contributing mechanisms. Eur J Pain 2003;7:9Y21 18. Gronblad M, Hurri H, Kouri JP: Relationships between spinal mobility, physical performance tests, pain intensity and disability assessments in chronic
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low back pain patients. Scand J Rehabil Med 1997; 29:17Y24 19. Camilotti BM, Rodacki AL, Israel VL, et al: Stature recovery after sitting on land and in water. Man Ther 2009;14:685Y9 20. Campbell JA, D’Aquisto LJ, Cline MG: Metabolic and cardiovascular response to shallow water exercise in young and older women. Med Sci Sports Exerc 2003; 35:675Y81 21. Yozbatiran N, Yildirim Y, Parlak B: Effects of fitness and aquafitness exercises on physical fitness in patients with chronic low back pain. Pain Clin 2004;16:35Y42 22. Becker BE, Cole MD: Comprehensive Aquatic Therapy. ed 2. Hillsboro, OR, Butterworth-Heinemann, 2004 23. Andersson GB: Epidemiological features of chronic low-back pain. Lancet 1999;354:581Y5 24. Haskell WL, Lee IM, Pate RR, et al: Physical activity and public health: Updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Circulation 2007;116:1081Y93 25. Ostelo RW, Deyo RA, Stratford P, et al: Interpreting change scores for pain and functional status in low back pain: Towards international consensus regarding minimal important change. Spine 2008;33:90Y4 26. Boonstra AM, Schiphorst Preuper HR, Reneman MF, et al: Reliability and validity of the visual analogue scale for disability in patients with chronic musculoskeletal pain. Int J Rehabil Res 2008;31:165Y9 27. Alonso J, Prieto L, Anto JM: The Spanish version of the SF-36 Health Survey (the SF-36 health questionnaire): An instrument for measuring clinical results. Med Clin 1995;104:771Y6 28. Ruta DA, Garratt AM, Wardlaw D, et al: Developing a valid and reliable measure of helath outcomes for patients with low back pain. Spine 1994;19(17): 1887Y96 29. Alonso J, Regidor E, Barrio G, et al: Valores poblacionales de referencia de la versio´n espan˜ola del Cuestionario de Salud SF-36. Med Clin (Barc) 1998; 111:410Y6 30. American College of Sports Medicine: Chapter 4: Health-related physical fitness testing and interpretation. In: ACSM’s Guidelines for Exercise Testing and Prescription. ed 8. Philadelphia, PA, Lippincott Williams & Wilkins, 2010, pp. 60Y105 31. Flo´rez Garcı´a MT, Garcı´a Pe´rez MA, Garcı´a Pe´rez F, et al: Transcultural adaptation of Oswestry low back pain disability questionnaire to Spanish population. Rehabilitacio´n 1995;29:138Y45 32. Gale CR, Martyn CN, Cooper C, et al: Grip strength, body composition, and mortality. Int J Epidemiol 2007; 36:228Y35 33. Jensky-Squires NE, Dieli-Conwright CM, Rossuello A, et al: Validity and reliability of body composition analysers in children and adults. Br J Nutr 2008; 100:859Y65
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34. Tabachnick BG, Fidell LS: Using Multivariate Statistics. Boston, MA, Harper & Row, 2006
postural responses of the trunk muscles. Exp Brain Res 2003;151:262Y71
35. Fairbank JC, Davis JB, Mbaot JC, et al: The Oswestry low back pain questionnaire. Physiotherapy 1980; 66:271Y3
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36. Collins SL, Moore RA, McQuay HJ: The visual analogue pain intensity scale: What is moderate pain in millimetres? Pain 1997;72:95Y7
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37. Maia Schlussel M, dos Anjos LA, de Vasconcellos MTL, et al: Reference values of handgrip dynamometry of healthy adults: A population-based study. Clin Nutr 2008;27:601Y7
49. Carpenter DM, Nelson BW: Low back strengthening for the prevention and treatment of low back pain. Med Sci Sports Exerc 1999;31:18Y24
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50. Payne N, Gledhill N, Katzmarzyk PT, et al: Healthrelated fitness, physical activity and history of back pain. Can J Appl Physiol 2000;24:236Y49
39. Hall AM, Kamper SJ, Maher CG, et al: Symptoms of depression and stress mediate the effect of pain on disability. Pain 2011;152:1044Y51
51. Takeshima N, Rogers ME, Watanabe E, et al: Water based exercise improves health-related aspects of fitness in older women. Med Sci Sports Exerc 2002; 34:544Y51
40. Turner JA, Jensen MP, Romano JA: Do beliefs, coping and catastrophizing independently predict functioning in patients with chronic pain? Pain 2000; 85:115Y25
52. Tsuji T, Matsuyama Y, Sato K, et al: Epidemiology of low back pain in the elderly: Correlation with lumbar lordosis. J Orthop Sci 2001;6:307Y11
41. Jensen MP, Romano JM, Turner JA, et al: Patients beliefs predict patients functioning: Further support for a cognitive-behavioural model of chronic pain. Pain 1999;81:95Y104 42. Poitras S, Loisel P, Prince F, et al: Disability measurement in persons with back pain: A validity study of spinal range of motion and velocity. Arch Phys Med 2000;10:1394Y400 43. Weiner DK, Haggerty CL, Kritchevsky SB, et al: How does low back pain impact physical function in independent, well-functioning older adults? Evidence from the Health ABC Cohort and implications for the future. Pain Med 2003;4:311Y20 44. Lin CW, Mc Auley JH, Macedo L, et al: Relationship between physical activity and disability in low back pain: A systematic review and meta-analysis. Pain 2011;152:607Y13 45. Barr KP, Griggs M, Cadby T: Lumbar stabilization: A review of core concepts and current literature, part 2. Am J Phys Med Rehabil 2007;86:72Y80 46. Hodges PW, Moseley GL, Gabrielsson A, et al: Experimental muscle pain changes feed forward
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53. Indahl A, Kaigle AM, Reikeras O, et al: Interaction between the porcine lumbar intervertebral disc, zygapophysial joints, and paraspinal muscles. Spine 1997;22:2834Y40 54. Hides JA, Stokes MJ, Saide M, et al: Evidence of lumbar multifidus muscle wasting ipsilateral to symptoms in patients with acute/subacute low back. Spine 1994; 19:165Y72 55. Hides JA, Richardson CA, Jull GA: Multifidus muscle recovery is not automatic after resolution of acute, first-episode low back pain. Spine 1996;21:2763Y9 56. Stump CS, Henriksen EJ, Wei Y, et al: The metabolic syndrome: Role of skeletal muscle metabolism. Ann Med 2006;38:389Y402 57. Wolfe RR: The underappreciated role of muscle in health and disease. Am J Clin Nutr 2006;84:475Y82 58. Thorstensen A, Carlson H: Fiber types in human lumbar back muscles. Acta Physiol Scand 1987;131: 185Y202 59. Moffroid MT: Endurance of trunk muscles in persons with chronic low back pain: Assessment, performance, training. J Rehabil Res Dev 1997;34:440Y7
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BRIEF REPORT
Affiliations: From the Department of Physical Education and Sport, University of Granada, Granada, Spain (PA´B-B, MD-F, AR-F); Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia (EGA); Department of Education, University of Almerı´a, Almerı´a, Spain (EGA); Department of Physiotherapy, Universidade Federal da Paraı´ba, Paraı´ba, Brasil (MCG-C); and Department of Physiotherapy, University of Granada, Granada, Spain (MA-M).
Correspondence: All correspondence and requests for reprints should be addressed to Manuel Delgado-Ferna´ndez, PhD, Departamento de Educacio´n Fı´sica y Deportiva, Facultad de Ciencias de la Actividad Fı´sica y el Deporte Universidad de Granada, Carretera de Alfacar, s/n, 18011, Granada, Spain.
Disclosures: Supported by a postdoctoral fellowship from the Spanish Ministry of Education (EX-2010-1008). Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/14/9307-0615 American Journal of Physical Medicine & Rehabilitation Copyright * 2014 by Lippincott Williams & Wilkins DOI: 10.1097/PHM.0000000000000123
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Exercise
Disability Predictors in Chronic Low Back Pain After Aquatic Exercise ABSTRACT Baena-Beato PA´, Delgado-Ferna´ndez M, Artero EG, Robles-Fuentes A, GattoCardia MC, Arroyo-Morales M: Disability predictors in chronic low back pain after aquatic exercise. Am J Phys Med Rehabil 2014;93:615Y623. The physical and psychological factors associated with reduction of disability after aquatic exercise are not well understood. Sixty participants (30 men and 30 women; age, 50.60 [9.69] yrs; body mass index, 27.21 [5.20] kg/m2) with chronic low back pain were prospectively recruited. The 8-wk aquatic therapy program was carried out in an indoor pool sized 25 6 m, with 140-cm water depth and 30-C (1-C) of water temperature, where patients exercised for 2Y5 days a week. Each aquatic exercise session lasted 55Y60 mins (10 mins of warm-up, 20Y25 mins of aerobic exercise, 15Y20 mins of resistance exercise, and 10 mins of cooldown). Demographic information, disability (Oswestry Disability Index), back pain (visual analog scale), quality-of-life (Short Form 36), abdominal muscular endurance (curl-up), handgrip strength, trunk flexion and hamstring length (sit and reach), resting heart rate, and body mass index were outcomes variables. Significant correlations between change in disability and visual analog scale (at rest, flexion, and extension), curl-up and handgrip (r ranged between j0.353 and 0.582, all Ps G 0.01) were found. Changes in pain and abdominal muscular endurance were significant predictors of change in disability after therapy. Key Words:
Disability, Chronic Low Back Pain, Muscle Endurance, Aquatic Exercise
D
isability is a complex concept covering impairments, activity limitations, and participation restrictions, reflecting the interaction between features of a person’s body and features of the society in which he/she lives.1 Patients with chronic low back pain (CLBP) experience clinical manifestations, including physical and psychological symptoms that affect their health status.2 Most low back painYrelated costs to society derive from patients’ disability, which is also the main determinant of patients’ quality-of-life (QoL).3,4 Disabilities are common in patients with CLBP,5 which is the third leading cause of chronic functional disability after respiratory conditions and injuries.6 Therefore, treating disability is as important as treating pain.7 Different therapeutic exercise programs have showed effectiveness to improve disability,8Y10 but the results are controversial.11 The factors interacting with physical measures of impairment in explaining disability and the relative Change in Disability After Aquatic Exercise
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extents to which psychological and physical factors account for improvements in outcome after therapy for CLBP have rarely been examined. Mannion et al.12 established explicative models of changes in disability promoted by therapeutic exercise, where changes in pain, psychological distress, and fearavoidance beliefs accounted for only 24% of the changes in disability after therapy. More precise and explicative models are needed to treat adequately this health problem. Disability in back pain is highly influenced by pain, physical impairment, and psychological and psychosocial factors.3,13 Patients with CLBP usually report that pain is their main problem and the main cause of their disability.3 In individuals with chronic disabilities, pain may induce serious psychological problems, negatively affecting QoL,14 where psychological distress has been identified as one potential pathway by which an episode of pain influences the development of persistent disabling symptoms.15 These factors explain only a portion of how CLBP affects disability, and other factors should be explored. There are evidences that exercise can decrease disability, pain, and secondary physical deconditioning in patients with CLBP,16 where physical treatments are based on the assumption that increased muscle strength, aerobic capacity, and stretching are crucial for the resumption of activities and for the reduction of disability.17,18 Previous studies have concluded that aquatic exercise may contribute to a decline in disability and pain and produce improved psychological and psychosocial factors.8,9 Aquatic exercise is of particular interest in CLBP because the unique properties of water reduce stress in joints and decrease axial loading of the spine.19 Moreover, continuous limb movements against the water resistance result in muscle strength20 and cardiovascular benefits.21 The aquatic environment enables the participant to perform movements that are normally difficult or impossible on land.22 Several studies indicate that therapeutic aquatic exercise can be a safe and effective treatment modality for patients with CLBP.9,10 There are no previous models to explain the clinical and physical factors involved in disability improvements after aquatic exercise programs in CLBP. To the best of the authors’ knowledge, no previous study has investigated the association between pain, QoL, and health-related fitness with disability in patients with CLBP after therapy. The aim of the study was to discover potential predictors of improvement disability in CLBP treated with aquatic exercise.
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METHODS Participants A total of 60 sedentary adults with CLBP (30 men and 30 women), defined as arising below the last rib margin and above the inferior gluteus lines and with a duration pain of greater than 12 wks, aged 50.60 (9.69) yrs, with body mass index (BMI) of 27.21 (5.20) kg/m2, volunteered to participate in this study. Participants were recruited in Massam Sport Center (Granada, Spain), and they received written and oral instructions about the intervention, the test protocol, and the possible risks and benefits of the study. Written informed consent was obtained before participation. The study was approved by the ethical committee of the University of Granada and was performed in accordance with the Helsinki Declaration, last modified in 2000. The inclusion and exclusion criteria for this study appear on Table 1. The study flow of participants is presented in Figure 1.
Treatment The 8-wk aquatic therapy program was carried out in an indoor pool sized 25 6 m, with 140-cm water depth, 30-C (1-C) of water temperature, where participants exercised for 2Y5 days a week. Each aquatic exercise session was conducted in small groups of 8 participants and lasted 55Y60 mins (10 mins of warm-up, 20Y25 mins of aerobic exercise, 15Y20 mins of resistance exercise, and 10 mins of cooldown). The resistance exercises progressed throughout the program by changing the number of repetitions per set (volume, 3 sets per 12 repetitions
TABLE 1 Inclusion and exclusion criteria Inclusion criteria: -Age between 25 and 64 yrs -Presence of self-reported low back pain for more than 12 wks23 Exclusion criteria: -Symptoms or signs that might suggest serious medical illness -Pregnancy or recent childbirth -Major rheumatologic, neurologic, neoplastic, or other conditions that may prevent full participation in the intervention -Previous spinal surgery, inflammatory, infectious, or malignant diseases of the vertebra -Presence of any psychiatric disorder that might affect the compliance and the assessment of symptoms -Presence of severe cardiovascular disease -Engagement in physical activity for 60 mins or longer per week during the last 12 mos24
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FIGURE 1 Flow of participants throughout the trial.
in the first week to 3 sets per 15 repetitions in the eighth week), by including specific resistance materials that increase the resistance offered by the water, and by increasing the velocity of the movements. Noodles and cuff devices were used for upper-body and lower-body exercises, respectively. Each training session included the following resistance exercises: hip flexion-extension, hip abduction-adduction, arms abduction-adduction at chest level, curl-ups, scissors leg, and backstroke kick with water noodle under the waist. The planning of the aerobic exercises was increased considering the intensity (Borg scale of 6Y20, 10Y12 in the first week to 12Y15 in the eighth week) and the volume (minutes). The aerobic exercises incorporated large muscle mass and consisted of lateral displacements, long-lever pendulumlike movements of the extremities, forward and backward jogging with arms pushing, pulling and pressing, leaps, kicks, leg crossovers and hopping movements focusing on traveling in multiple directions, and bounding off the bottom of the pool. Heart rate was assessed using the POLAR 610 heart-rate monitor (Polar Electro OY, Finland) at different moments of the program when patients were out of the pool. Participants were monitored in different sessions to assess if the intensity recommendations were followed. At the end of each session, static stretching www.ajpmr.com
techniques were performed for gluteus, lumbar back, and hamstrings, as part of the cooldown. Sessions were supervised by physical therapists with more than 6 yrs of experience in the management of CLBP through aquatic exercise programs.
Outcome Measures To assess changes in different parameters after aquatic exercise, all measurements were taken at baseline and 24 hrs after discharge in the aquatic exercise program.
Questionnaires Participants were evaluated for the following self-completed questionnaires.
Oswestry Low Back Pain Disability Questionnaire The Spanish version of the Oswestry low back pain disability questionnaire26 was used. The reliability and validity of this questionnaire have been found to be acceptable,26 and the minimal clinical change is considered to be 10%.27
Visual Analog Scale Back pain was assessed at rest and during movement of the trunk (flexion and extension) using a Change in Disability After Aquatic Exercise
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visual analog scale (VAS). The reliability and validity of VAS have been found to be acceptable,28 and the minimal clinical change is considered to be 15 mm.29
Short Form 36 Health Survey The Spanish version of Short Form 36 (SF-36) is a generic instrument assessing health-related QoL.29 It contains 36 items and yields 8 domains (parameters). These 8 parameters can be used to derive 2 composite scoring summaries: physical composite summary (PCS SF-36, physical functioning, physical role, bodily pain, and general health perceptions) and mental composite summary (MCS SF-36, vitality, social functioning, mental health, and emotional role). The SF-36 is a sensitive measure of treatment success in patients with low back pain.30 Each domain is scored on a scale from 0 (worst possible health) to 100 (best possible health).31
Fitness Outcomes Participants were evaluated in fitness for curl-up test, handgrip strength, sit and reach test, and resting heart rate. BMI was also measured. All testing sessions were conducted by the same experimented researcher.
Curl-up Test Abdominal muscular endurance was measured using the curl-up test.25 The cadence for the test was 40 beats/min, paced by a metronome. The test was terminated when the subject was unable to maintain the required cadence or unable to maintain the proper curl-up technique for 2 consecutive repetitions despite feedback from the researcher. The highest number of repetitions completed while maintaining proper form was recorded.
Handgrip Strength Test A hand dynamometer with adjustable grip was used (TKK 5101 Grip D; Takey, Tokyo, Japan). The test was performed twice, and the maximum score for each hand was recorded in kilograms. Optimal grip was noted for each participant in the pretest and repeated in the posttest. The sum of the scores achieved by the left and right hands was used in the analysis.32
Sit and Reach Test Trunk flexion and hamstring length were determined via the sit and reach test, as described by the American College of Sport Medicine’s protocol.25
Resting Heart Rate Participants were instructed in the procedure of measuring their pulse rate and then were asked
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to register resting heart rate manually at home, from the carotid artery using a stopwatch. They registered resting heart rate in four nonconsecutive days during pretest and posttest weeks. The mean heart rate among the four measurements was used as resting heart rate before and after the intervention.
Body Mass Index Weight (kilograms) was measured using Octapolar bioimpedance analyses (Biospace Inbody 720; Biospace Company, Ltd, Seoul, Korea). Biospace Inbody Analyse has been found to be reliable.33 Height (meters) was measured in the Frankfurt plane with a telescopic height-measuring instrument (Type SECA 225; range, 60Y200 cm; precision, 1 mm). BMI was calculated (kg/m2).
Statistical Analyses Mean and 95% confidence interval were reported for continuous variables with a normal distribution. Normal distribution of data was checked using Kolmogorov-Smirnov test. A t paired test was carried out to show the difference between baseline and postintervention data. Pearson and Spearman correlation analyses were applied whenever appropriate. The correlation analyses were carried out between the change (,), postdifference-predifference at baseline (pretest) and follow-up (posttest), in the disability (Oswestry Disability Index, ODI), back pain (VAS at rest), PCS SF-36 and MCS SF-36, abdominal muscular endurance (curl-up), handgrip strength, trunk flexion and hamstring length (sit and reach), resting heart rate, and BMI, after the physical therapy program. The assumptions of normality, linearity, and homoscedasticity were investigated by the residual scatterplots. Stepwise multiple regression analysis was used to explore which variables could explain the variation in disability (dependent variable). The changes in back pain, health-related QoL, abdominal muscular endurance, handgrip strength, trunk flexion and hamstring length, resting heart rate, and BMI were considered independent variables. The requirements of an independent variable to be included in the multiple regression analysis were as follows: (1) the correlation coefficients between the dependent variable and the independent variables were significant and r Q 0.25, and (2) the correlation coefficients between the independent variables were r e 0.7.34 Finally, the final model was validated using bootstrapping. Specifically, the bootstrapping method was carried out with repeated samples of the same size as the original samples in replacement. Two thousand replications were produced to estimate bootstrap bias-corrected and accelerated
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confidence intervals. For statistical analyses, significance level was set at P G 0.05. All analyses were performed using R software (2.9.3).
RESULTS Forty-one percent of the participants had an educational status of unfinished studies and primary school, and 59% had secondary school and a university degree; 75% of the participants listed civil status as married. Occupational status was distributed as housewife, 23%; working, 42%; retired, 22%; and unemployed, 13%. All participants were white from Granada metropolitan area. Participants showed moderate disability (mean [SD], 29.3 [13.4]),35 pain was from moderate to intense (mean [SD], 6.20 [2.23]),36 PCS SF-36 was low (mean [SD], 35.9 [9.89]),31 MCS SF-36 was moderate (mean [SD], 50.2 [11.4]),31 curl-up was low (mean [SD], 12.4 [5.41]),25 handgrip test was from low to moderate (mean [SD], 69.4 [20.2]),37 and sit and reach test was very low (mean [SD], 9.15 [9.86]),25 with BMI of overweight (mean [SD], 27.2 [5. 20])25 and resting heart rate (mean [SD], 69.4 [8.88]).38 Table 2 shows the baseline and postintervention scores.
Correlational Analyses Significant positive correlations between change in disability and VAS at rest (r = 0.582, P G 0.01), VAS at flexion (r = 0.410, P G 0.01), and VAS at extension (r = 0.424, P G 0.01) were moderate. Significant negative correlations were also found between change in disability and change in curl-up (r = j0.353, P G 0.01), and change in disability and change in handgrip strength (r = j0.431, P G 0.01) were moderate.
In addition, significant correlations existed among the independent variables (j0.353 G r G 0.582; see Table 3), but none was considered to be multicollinear (defined as r 9 0.70); therefore, each one was included in the regression analyses.
Regression Analyses Stepwise regression analyses revealed that changes in back pain intensity and abdominal muscular endurance were independent and significant predictors of change in disability after aquatic exercise, and when combined, they explained 48% of the variance (see Table 4).
DISCUSSION Current findings suggest that changes in back pain intensity and abdominal muscular endurance after 8 wks of aquatic exercise program have a relevant contribution to changes in CLBP-related disability. Disability related to CLBP may be caused by pain, physical impairment, psychological distress, and psychosocial factors.3,39 This study is the first to specifically examine disability determinants related to pain intensity and abdominal muscular endurance, after a treatment based on aquatic exercise program. Because rehabilitation strategies are focused on reducing pain and clinical repercussions from CLBP, particularly disability, understanding potential determinants for reduced disability may assist in the rehabilitation process in these patients. We observed that ODI and back pain (VAS) decreased in the participants beyond the minimal clinical change accepted in patients with low back pain,27 where they improved their levels from baseline
TABLE 2 Effects of an 8-wk aquatic therapy program in adults with CLBP Pretest, Posttest, Mean T SEM Mean T SEM ODI, scores of 0Y100
29.3 T 13.4
VAS rest, cm, 0Y10 VAS flex, cm, 0Y10 VAS ext, cm, 0Y10 PCS SF-36, scores of 0Y100
6.20 T 6.30 T 5.18 T 35.9 T
2.23 2.32 3.05 9.89
MCS SF-36, scores of 0Y100 Curl-up, no. repetitions HS, kg SR, cm HRR, ppm BMI, kg/m2
50.2 T 12.4 T 69.4 T 9.15 T 69.4 T 27.2 T
11.4 5.41 20.2 9.86 8.88 5.20
P
Minimum and Maximum Values in Healthy Adults
16.8 T 11.3 G0.0001 Minimal functional limitation G 20 to maximal functional limitation 9 8035 2.65 T 2.11 G0.0001 Mild to moderate pain G 4 to severe 9 636 2.43 T 2.14 G0.0001 1.85 T 2.15 G0.0001 44.9 T 9.08 G0.0001 Lowest possible score of 0 to highest possible score of 10031 50.1 T 9.56 0.932 20.8 T 5.83 G0.0001 Need improvement, 5, to excellent, 2525 75.1 T 20.5 G0.0001 Very poor, e59, to excellent, 910737 13.5 T 9.54 G0.0001 Need improvement, 17, to excellent, 3525 64.8 T 7.78 G0.0001 Bradycardia (G40Y45), tachycardia (990Y95)38 26.8 T 5.01 G0.0001 Normal, 18.5Y24.9, to overweight, 25.0Y29.925
HRR, heart rate at rest; HS, handgrip strength; SR, sit and reach; VAS ext, VAS at extension; VAS flex, VAS at flexion; VAS rest, VAS at rest.
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TABLE 3 Pearson product-moment correlation matrix for study variable , ODI , , , , , , , , , ,
ODI PCS SF-36 VAS rest VAS flex VAS ext HS SR BMI HRR curl
1.00 j0.009 0.582a 0.410a 0.424a j0.431a j0.193 0.058 0.242 j0.353a
, PCS SF-36
, VAS rest
, VAS flex
, VAS ext
, HS
, SR
, BMI
, HRR , Curl
V V V V V V V V 1.00 V V V V V V V j0.164 1.00 V V V V V V j0.446a 0.625a 1.00 V V V V V j0.076 0.655a 0.570a 1.00 V V V V b a 0.314 j0.355 j0.373a j0.385a 1.00 V V V 0.215 j0.141 j0.221a j0.015 0.348a 1.00 V V 0.114 0.244 0.072 0.199 0.095 j0.125 1.00 V j0.018 0.223 0.305b 0.150 j0.481a j0.176 j0.098 1.00 b 0.023 j0.039 j0.314 j0.153 0.288b 0.206 0.182 j0.349a
V V V V V V V V V 1.00
a
P G 0.01. bP G 0.05. ,, change between postdifference-predifference at baseline (pretest) and follow-up (posttest); HRR, heart rate at rest; HS, handgrip strength; SR, sit and reach; VAS ext, VAS at extension; VAS flex, VAS at flexion; VAS rest, VAS at rest.
in 43% in ODI, 57% in VAS at rest, 61% in VAS in flexion, and 64% in VAS in extension. The authors also observed an increase of 20% in the physical domains of health-related QoL (PCS SF36), and MCS SF36 showed a very slight decrease of less than 1%, but the differences before and after the intervention were not statistically significant (see Table 2). These changes were accompanied by improvements in fitness and BMI, where participants obtained improvements of 68% in the curl-up test (moved from low to good level),25 8% in the handgrip test (moved from low to medium level), 47% in the sit and reach test,25 6.6% in the heart rate at rest,38 and 2% in BMI keeping in overweight.25 To the best of the authors’ knowledge, only one study has investigated predictor’s variables in disability after therapy in patients with CLBP.12 Mannion et al.12 (2001) also reported a model where pain, psychological distress, and fear-avoidance belief accounted for 24% of the variance in disability after treatment. The study’s model was able to explain in total 48% of the variability in disability after therapy in patients with CLBP, where a reduction of pain intensity combined with an improvement in abdominal muscular endurance could contribute to reducing disability. Patients with CLBP usually report that pain is their main problem and the main cause of their disability.3 In the present study, change in pain is the variable with the largest contribution (33%) to the total explained variance; this was reflected by higher back pain intensity in patients with CLBP reporting greater disability. These results are in accordance with previous studies using multivariate analysis to predict disability, which have shown that pain normally explains the greatest or second
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greatest proportion of the variance.12,13,40,41 The relationship between disability and pain is bidirectional and a complex process, as disability is a symptom of pain resulting in loss of function. Back pain may lead to disability through its effects on physical impairment42 and psychological distress.15 It is often assumed that patients who feel more disabled and thus report more daily life restrictions caused by pain intensity43 will be those who are less physically active in CLBP.44 This is reflected in treatments recommended for CLBP, which typically promote increased physical activity to aid recovery and reduce pain intensity and disability. Abdominal muscle endurance was a significant and relative new determinant of disability in the present study (15% to the total explained variance in disability after therapy) and was one of the few physical factors that retained its importance when considered in combination with the pain. One important risk factor for low back pain is weakness of abdominal muscles,45,46 and strengthening of these is often associated with significant improvements of CLBP as well as with decreased functional disability.47Y49 Abdominal muscular endurance is suggested to be reduced in patients with CLBP,50 because weakened abdominal muscles cannot maintain normal inclination of the pelvis, which increases lordosis of the lumbar spine,51 and an increase of lumbar lordosis has shown to be inversely correlated with pain.52 Changes in muscle activity have been observed in experimental53 and clinical studies54 induced by pain, where reflex inhibition is suggested to play a role.55 The role of muscular strength in the performance of activities of daily living (sitting, standing, lifting, or rolling over in bed), as well as in the prevention of chronic disease, is increasingly
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A, regression coefficient; ,, change between postdifference-predifference at baseline (pretest) and follow-up (posttest); r 2, variability of disability explained by the respective predictor in percent; VAS rest, VAS at rest.
32.7 15.3 0.190 G0.0001 G0.0001 1.326 6.241 j3.939 3.335 2.256 j0.935 j1.141 to 7.850 1.596Y2.945 j1.413 to j0.552 Interceptil , VAS rest , curl
3.359 2.263 j0.937
j1.712 to 8.430 1.537Y2.989 j1.414 to j0.461
0.597 j0.376
r2 (%) P t Standardized Coefficients, A Bootstrap, A Bootstrap BCA, 95% CI 95% CI for A Unstandardized Coefficients, A Independent Variables
TABLE 4 Summary of stepwise regression analyses to determine predictors of improvement in disability (r 2 = 48%)
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being recognized.56,57 There is an association between abdominal muscle endurance and disability, where qualitative changes in posture58 and movement can occur dramatically and spontaneously because of gradual changes in parameters of abdominal muscular endurance, resulting in some degree of disability hindering the patient to perform activities of daily living.59 The authors recognize some limitations of the study. They included a relatively small sample size (n = 60). However, because of the small sample size, the number of independent variables entered in the regression analysis was limited to reduce the likelihood of a type II error. Other relevant outcomes such as lumbar musculature endurance levels should be examined in future research to provide more global information about the relationship between physical condition and disability. Long-term outcomes were not performed in these subjects so it cannot be determined whether the effect of the treatment can be maintained over time. Another limitation may be that group interaction or attention from the therapist gave positive feeling to the participants.
CONCLUSIONS Changes in pain intensity and abdominal muscular endurance were significant predictors of change in disability in patients with CLBP after therapy. Aquatic exercise decreases levels of disability and back pain, increases QoL, and improves BMI and fitness in sedentary adults with CLBP. Therapists working with patients with CLBP should take into account these relationships to improve the management of CLBP-related disability. ACKNOWLEDGMENTS
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