JSR GALLEY PROOF

Journal of Sport Rehabilitation, 2009, 18, 1-16 © 2009 Human Kinetics, Inc.

Laboratory Gait Analysis in Patients With Low Back Pain Before and After a Pilates Intervention Juliana Limba da Fonseca, Marcio Magini, and Thais Helena de Freitas Objective: To evaluate the influence of pain on vertical ground-reaction force (VGRF) in patients with low back problems and the effect of the Pilates method on the gait of these patients. Design: A single-blind randomized controlled trial. Participants: 28 individuals assigned to a control group (n = 11) and a low-back group (n = 17), the latter of which was subdivided into a Pilates group (n = 8) and a no-Pilates group (n = 9). Intervention: The Pilates group undertook 15 sessions of Pilates. Main Outcome Measures: The VGRF parameters were recorded during preferred and faster walking speeds. The data were collected before and after the intervention. Results: The weight-acceptance rate and push-off rate were significantly less in the right lower limb of low-back group than of the control group at preferred speed. Improvements were seen in the Pilates group postintervention, with increased middle-support force for the left lower limb at faster walking speed and decreased pain; this did not occur in the no-Pilates group. Conclusions: These results suggest that patients with low back pain use strategies to attenuate the amount of force imposed on their body. The Pilates method can improve weight discharge in gait and reduce pain compared with no intervention. Keywords: vertical ground-reaction force, exercise therapy, rehabilitation

Low back pain is the most common of all skeletal-muscle problems. It has been estimated that 80% of adults at least once in their lives will suffer an episode of back pain sufficiently severe that it will make them stop working temporarily.1 Two syndromes might be recognized: common low back pain and low back pain with referred leg pain. In common low back pain, no important irradiation occurs, but in low back pain with referred leg pain, the pain is spread to the buttocks, posterior face of the thigh, and the feet.2 The etiology of low back pain is not clearly definite because of multiple risk factors associated with the condition. Some of these factors are repetitive motion, curvature and torsion of the spine, pushing and pulling activities, stumbles, falls, and static or sitting work posture.3 One important mechanical function of the lumbar spine is to support the upper body by transmitting compressive and shearing forces to the lower body

Fonseca is with the Dept of Biomedical Engineering; Magini, the Research and Development Institute; and de Freitas, the Dept of Health Sciences, Paraíba Valley University, São José dos Campos, Brazil.    1

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during the performance of everyday activities. To enable the successful transmission of these forces, mechanical stability of the spinal system must be ensured.4 The lumbar musculature has an effective role in the mechanical stability of the spinal system, reducing abrupt kinematic behaviors and consequent lesions.5 Low back pain has been associated with the dysfunction and weakness of deep abdominal muscles. These deeper abdominal muscles, including the transversus abdominis, multifidus, and pelvic-floor muscles, will be referred to throughout this article as the core muscles. Imaging techniques have identified multifidus6,7 and transversus abdominis8 alterations in patients with low back pain. Recent research demonstrated that specific exercises targeting the multifidus and transversus abdominis contribute to pain relief and reduce recurrence of low back pain.9,10 The mechanism for pain relief with this specific exercise approach is believed to be through enhanced stability of the lumbar-spine segments.11 The Pilates method involves specific training of deep abdominal muscles to increase tonus and strength of those muscles, decreasing erosion and stress on joints of the backbone.12 It is a complete program of mental and physical conditioning13 and is highly recommended by doctors, physiotherapists, and other practitioners all over the world,14 sometimes specifically to treat patients with chronic low back pain.15 Nonetheless, there is little evidence in the literature that corroborates the efficacy of the Pilates method in low-back-pain treatment. A study to evaluate the effect of Pilates on patients with chronic low back pain demonstrated that the method might be efficient for general health, sports functioning, flexibility, proprioception, and a decrease in pain.16 Laboratory gait analysis has been broadly used by researchers17–25 to enhance the understanding of normal gait and pathological characteristics. Alterations in the gait parameters of patients with low back pain have been indicated by published research: decrease of speed,20,21,23,26 alteration in lumbar-muscle electromyographic activity,22 asymmetrical patterns,20 disorders in torso rotation,23,26 decrease of step and stride length,20 longer duration of support stage, and shorter duration of balance.22 The influence of low back pain on vertical ground-reaction force (VGRF) is not clear. A study of gait on a force platform demonstrated that patients with low back pain and a control group did not differ on VGRF parameters, whereas patients with low back pain and lower limb pain showed significant decreases of all parameters (apart from the first peak force) when walking at their preferred speed.27 The objectives of the current study were to evaluate the influence of pain on VGRF during gait execution of patients with low back problems and the effect of a Pilates program on the gait of these patients. To study the influence of pain on gait characteristics in patients with low back pain, we compared results of a control group (without pain) and a low-back group. To evaluate the influence of Pilates in patients with low back pain through gait analysis, after analysis between the control group and the low-back group, the low-back group was subdivided into a Pilates group and a no-Pilates group (a group without intervention). After 15 sessions of Pilates, a new data collection was done in the Pilates group and the no-Pilates group to identify any significant changes from preintervention to postintervention within each group.

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Methods The study was a single-blind randomized controlled trial. Ethical approval for the study was obtained from the Paraíba Valley University ethics committee. All the participants were informed of the experiment, being made aware of the objectives, risks, benefits, and purposes of the current study, as well as their ability to suspend or interrupt any stage of the procedure if they wished. After these explanations, all the participants signed a consent form. The low-back-pain group was selected from the waiting list for physiotherapeutic treatment in the Health Science College of Paraíba Valley University. Ten participants were sent for the project through medical orientation. The control group consisted of students and staff of the university.

Participants A total of 28 individuals were recruited for the study. Initially, the participants were divided into 2 groups. A control group consisted of 11 healthy individuals (4 men and 7 women) with no complaint of back pain or musculoskeletal pain, average age 25.36 ± 5.85 years, average height 1.69 ± 0.08 m, and average weight 66.87 ± 14.32 kg. The second group consisted of 17 individuals complaining of low back pain (5 men and 12 women), average age 33.12 ± 11.61 years, average height 1.64 ± 0.07 m, and average weight 65.56 ± 12.11 kg. After analysis between the control and low-back groups, the low-back group was subdivided into 2 groups: a group of 9 participants with low back pain who did not submit to any type of intervention (no-Pilates group), average age 34.4 ± 13.1 years, average height 163.2 ± 6.9 m, and average weight 66.2 ± 10.7 kg, and a group of 8 patients undertook a Pilates program, average age 31.6 ± 10.3 years, average height 165.8 ± 6.3 m, and average weight 64.9 ± 14.3 kg. The organization of the groups is presented in Figure 1. The measures were taken using the same methodology in all groups.

Figure 1 — Organization of the groups. Abbreviations: CG, control group; LBG, lowback group; PG, Pilates group; NPG, no-Pilates group.

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The inclusion criteria were independent gait execution without the use of any support device (crutch, walking stick, etc), complaints of low back pain for at least 6 months (low-back group), no complaints of low back pain or musculoskeletal pain (control group), and being between 18 and 59 years old. Exclusion criteria included neurological disease, major visual deficits, true leg-length discrepancy greater than 2 cm, and history of ankylosing spondylosis, disc herniation, tumor, infection or fracture, cauda equina syndrome, spine-fusion surgery, or any lower extremity orthopedic surgery within 1 year of the beginning of the study. In the control group, all the participants were right-side dominant; in the low-back group 15 participants were right-side dominant and 2 were left-side dominant. No participants in the no-Pilates group or the Pilates group were undergoing regular physiotherapy or any further treatment during the time of the study, aside from medication for conditions unrelated to the study. Both groups were encouraged to make no changes to their normal exercise or activities.

Equipment All participants walked on a Gaitway System instrumented treadmill with a force platform that holds a piezoelectric sensor system by Kistler Inc. Mats and a 55-cm Gynasticball therapeutic ball by Carci were used for Pilates exercises.

Preparation Procedures All participants were assessed for leg-length discrepancy (the distance from the anterior superior iliac spine to the ipsilateral medial malleolus of each leg, in a supine position). The low-back group filled out a questionnaire regarding their history of back pain. It required quantitative answers regarding weekly episodes of back pain, history of medication use, and whether they had back pain with lower limb pain (Table 1). A visual analog pain scale and present pain intensity28 were analyzed for the purpose of evaluating the clinical parameters of success or failure of treatment. On the visual analog pain scale, 0 = no pain and 10 = most severe pain. As for present pain intensity, participants described the pain as excruciating (5 points), horrible (4 points), distressing (3 points), uncomfortable (2 points), mild (1 point), or no pain (0 point).

Data-Collection Procedures The data were collected during 2 walking-speed conditions: preferred and fastest speeds. All the participants wore tennis shoes and their preferred clothes during data collection. Body weight was obtained by the force platform with the participant in a static upright standing position. First, we determined participants’ preferred walking speed and whether they were able to walk at the stipulated speed of 5.5 km/h. Participants started walking on the treadmill at an initial speed of 1 km/h, and every 30 seconds the speed was increased 0.5 km/h. They were instructed to report the speed at which they walked most comfortably, that is, their preferred walking speed. The participants walked on the treadmill up to the fastest speed of 5.5 km/h or up to the highest speed they were able to. Afterward, the treadmill speed was decreased by 1 km/h every 30 seconds to the final speed of 1

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Table 1  Occurrence of Referred Leg Pain in the Low-Back Group Group Pilates   patient 1   patient 2   patient 3   patient 4   patient 5   patient 6   patient 7   patient 8 No Pilates   patient 1   patient 2   patient 3   patient 4   patient 5   patient 6   patient 7   patient 8   patient 9

Left lower limb

Right lower limb

no no no yes no yes no no

no no no no no yes no no

no no no no no yes no yes yes

yes no no no no yes yes yes yes

km/h, and the treadmill was stopped. After a rest (5 to 10 minutes) participants walked on the treadmill again. Treadmill speed was increased from 1 km/h until the previously determined preferred walking speed, following the same parameters as the previous procedure. After this, a 10-minute period of adaptation was given, so that the values presented by the gait on the treadmill could be compared with the values presented for the fixed platform.29 After 10 minutes of gait execution, the first data collection was performed at the preferred walking speed. Right after the first collection, the treadmill speed was increased until the fastest speed of 5.5 km/h or up to the maximum speed the participant was able to achieve. Then, data were collected at the fastest speed. The speed was decreased again in similar steps. The sampling frequency of treadmill data was standardized at 1000 Hz. At each velocity level, data were collected during 10 seconds, in a range of 1 minute. The data were collected at the beginning of the first minute. After the Pilates group undertook 15 Pilates sessions, they submitted to another data collection on the treadmill, along with the no-Pilates group, that was conducted under the same conditions as the first collection.

Outcome Measures The parameters related to VGRF were analyzed. This component is representative of values of all active forces in the body, which produces a resultant in the vertical direction.30 These parameters are defined as follows.

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• First peak force: maximum absolute value for the first curve of vertical force peak versus each step time duration, when the heel touches the ground. • Second peak force: maximum absolute value for the second vertical peak force versus each step time duration, when the foot is taken off the ground. • Middle-support force: minimum absolute value between the first and second vertical force peaks versus time taken during each step (occurs during the unilateral stance phase, when the body is supported by only 1 leg). • Weight-acceptance rate: the first-peak-force value divided by the time for the first peak, showing how much the force varies according to the time the heel touches the ground. • Push-off rate: second peak force divided by the time taken to reach the second peak, showing how much the force varies according to the moment of taking the foot off the ground.31 The parameters were normalized by the body weight (in Newtons) of each individual. The value of the data takes account of the significant numbers of their absolute value.

Intervention After the data collection on the treadmill, the Pilates group performed 15 sessions of Pilates exercises, 2 sessions per week. The sessions lasted for an hour and were performed individually. The exercise program was taught by a certified Pilates instructor. The no-Pilates group continued with their normal activities and did not undergo any other type of treatment aside from medication taken for conditions not related to the study. All the participants in the Pilates group fulfilled the same program of exercises. The program of exercises consisted of 4 stages11: 1. Isolated contraction training of the core muscles 2. Cocontraction of the core muscles, that is, simultaneous contraction of the transversus abdominis, multifidus, and pelvic-floor muscles 3. Cocontraction of the core muscles combined with limb movements, keeping the spine static 4. Cocontraction of the core muscles during dynamic functional movements of the trunk The participants were instructed to recruit the core muscles during the exercises and not to substitute them for global muscles. The exercise program consisted of basic-level Pilates exercises, progressing from positions with low loads (supine position, prone position, and side-lying) to more functional body positions with gradually increasing external loads (box and sitting positions). The participants were instructed to maintain aligned and symmetrical posture of the spine and limbs and to perform the exercises with the spine neutral. The exercises were taught by appropriate verbal instructions given by the instructor. The participants were instructed to inform the instructor if they experienced any pain, discomfort, cramps, or incapacity to maintain the contraction of the core muscles or neutral spine. In those cases, the exercise was interrupted and, if necessary, modified by decreasing lever lengths for any individual participants who found the

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particular exercise too challenging to enable them to maintain neutral spine. If participants felt loss of control for a movement, they were advised to go back to a base position for that particular exercise. Until the seventh session, homework was assigned so that cocontraction of the core muscles would become automatic and efficient. Those exercises were indicated to be performed once a day. From the eighth session on, the participants were encouraged to activate these muscles regularly during daily activities (while walking, watching TV, etc).

Statistical Analysis Data are expressed as mean ± SD. Because the number of participants in this study is restricted to test whether the values of the data present normal distribution in the population, nonparametric tests were performed.32 However, nonparametric tests are trustworthy and conclusive for this number of participants. Differences between the control group and the low-back group were analyzed using a Mann– Whitney U test. A t test by Wilcoxon was used to identify any significant changes from preintervention to postintervention within the Pilates group and the no-Pilates group. Statistical significance was set at P = .05.

Results All participants completed the trial. No significant differences were found between the control group and the low-back group in baseline data for age, height, and weight. There were no significant differences between the Pilates group and the no-Pilates group in baseline data for age, height, weight, visual analog pain scale (Pilates = 5.9 ± 2.0 and no Pilates = 6.1 ± 1.8), and present pain intensity (Pilates = 2.8 ± 1.5 and no Pilates = 2.0 ± 0.7). In the control group all the participants were able to walk at the speed of 5.5 km/h. In the low-back group, 4 participants were not able to walk at that speed: 2 walked at the speed of 5.0 km/h, and 2 others at 4.5 km/h. However, the statistical analysis did not identify significant differences between the control group (preferred walking speed = 3.55 ± 0.72 km/h and fastest walking speed = 5.5 ± 0 km/h) and the low-back group (preferred walking speed = 3.09 ± 0.37 km/h and fastest walking speed = 5.32 ± 0.35 km/h).

Gait Analysis Between the Control Group and the Low-Back Group The statistical analysis showed significant differences between the control group and the low-back group. The low-back group had lower mean values for weightacceptance rate (460% ± 105% body weight) and push-off rate (612% ± 157% body weight) of the right lower limb than the control group (weight acceptance rate = 549% ± 134% body weight, and push-off rate = 727% ± 159% body weight) when walking at the preferred speed (Figures 2 and 3). The other parameters did not show significant differences between the groups (Table 2). The control and low-back groups did not differ significantly in VGRF during the fastest walkingspeed condition (Table 3).

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Figure 2 — Weight acceptance rate (WAR) of the control group (CG) and low-back group (LBG) in the right lower limb (RLL). Data are expressed as means. *Significant difference between control and low-back groups.

Figure 3 — Push-off rate of the control group (CG) and low-back group (LBG) in the right lower limb (RLL). Data are expressed as means. *Significant difference between control and low-back groups.

Gait Analysis After the Intervention After Pilates sessions, the statistical analysis demonstrated that in the Pilates group there was a significant increase of the middle-support force of the left lower limb during the fastest walking-speed condition (Figure 4). Tables 4 and 5 describe the Pilates group’s force parameters before and after Pilates sessions, during preferred and fastest walking speeds, respectively. In the no-Pilates group, the statistical analysis did not show significant differences in the force parameters after the intervention period. Tables 6 and 7 illustrate the values for the no-Pilates group preintervention and postintervention during preferred and fastest walking speeds, respectively.

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Table 2  Vertical-Ground-Reaction-Force Parameters at Preferred Walking Speed in the Control and Low-Back Groups, Mean ± SD Control Group Parameter First peak force Second peak force Middlesupport force Weightacceptance rate Push-off rate

Left lower limb Right lower limb

Low-Back Group Left lower limb Right lower limb

100% ± 4%

100% ± 5%

98% ± 4%

98% ± 4%

107% ± 6%

104% ± 6%

103% ± 6%

102% ± 5%

82% ± 6%

82% ± 5%

85% ± 4%

84% ± 3%

561% ± 142%

549% ± 134%

479% ± 138%

460% ± 105%*

765% ± 181%

727% ± 159%

631% ± 173%

612% ± 157%*

*Significant difference between control and low-back groups.

Table 3  Vertical-Ground-Reaction-Force Parameters at Fastest Walking Speed in the Control and Low-Back Groups, Mean ± SD Parameter

Control Group

Low-Back Group

Left lower limb Right lower limb

Left lower limb Right lower limb

First peak force 111% ± 5% Second peak 113% ± 7% force Middle-support 66% ± 5% force Weight1220% ± 458% acceptance rate Push-off rate 1087% ± 55%

111% ± 5% 112% ± 7%

105% ± 8% 108% ± 9%

106% ± 6% 107% ± 8%

66% ± 4%

66% ± 6%

66% ± 6%

1196% ± 575%

1142% ± 279%

1191% ± 532%

1059% ± 92%

999% ± 151%

986% ± 135%

Clinical Parameters After the Intervention In relation to clinical parameters (visual analog pain scale and present pain intensity), in the Pilates group all the parameters showed a significant decrease (Table 8). In the no-Pilates group the statistical analysis did not identify differences after the intervention period.

Discussion The results presented here were obtained from measures of gait parameters. We believe that clinicians and researchers might be able to more objectively evaluate factors that might affect patients with low back pain and measure the effects of interventions designed to modify these parameters.

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Figure 4 — Middle-support force (MSF) of the Pilates group in the left lower limb. Data are expressed as means. *Significant difference in the Pilates group before and after the intervention.

Table 4  Vertical-Ground-Reaction-Force Parameters at Preferred Walking Speed in the Pilates Group Before and After Pilates Sessions, Mean ± SD Left Lower Limb Parameter First peak force Second peak force Middle-support force Weight-acceptance rate Push-off rate

Right Lower Limb

Before

After

Before

After

99% ± 4% 104% ± 7% 83% ± 5% 517% ± 170% 634% ± 210%

97% ± 5% 105% ± 8% 81% ± 6% 522% ± 184% 660% ± 214%

99% ± 4% 103% ± 5% 83% ± 4% 469% ± 127% 631% ± 193%

96% ± 5% 104% ± 8% 82% ± 5% 472% ± 130% 647% ± 205%

The findings from the current study indicate that the VGRF parameters (weight-acceptance rate and push-off rate of the right lower limb) of the low-back group were significantly less than those of the control group during the preferred walking-speed condition. Observing Table 1, we can see that within the low-back group, most of the participants with leg pain had the referred pain in the right lower limb. These results suggest that when walking at preferred speed, those with referred leg pain seem to use additional strategies to decrease the amount of force imposed on their painful leg, which is in agreement with previous work on this subject.27 In contrast to the previous reports,20,21,23,26,27 gait speed was not reduced in the low-back group. Individuals with low back pain in this study had only moderate levels of pain, levels that might not be severe enough to cause them to significantly decrease speed or alter other gait parameters. Certainly in future studies, patients with a higher level of pain should be used.

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Table 5  Vertical-Ground-Reaction-Force Parameters at Fastest Walking Speed in the Pilates Group Before and After Pilates Sessions, Mean ± SD Left Lower Limb

Right Lower Limb

Parameter

Before

After

Before

After

First peak force Second peak force Middlesupport force Weightacceptance rate Push-off rate

109% ± 6%

110% ± 7%

107% ± 4%

111% ± 7%

109% ± 8%

109% ± 8%

108% ± 6%

110% ± 5%

63% ± 8%

66% ± 8%*

65% ± 7%

66% ± 8%

1219% ± 290%

1121% ± 309%

1411% ± 689%

1282% ± 541%

1040% ± 103%

1053% ± 149%

1037% ± 76%

1037% ± 99%

*Significant difference within Pilates group before and after the intervention.

Table 6  Vertical-Ground-Reaction-Force Parameters at Preferred Walking Speed in the No-Pilates Group Before and After the Intervention, Mean ± SD Left Lower Limb Parameter First peak force Second peak force Middle-support force Weight-acceptance rate Push-off rate

Right Lower Limb

Before

After

Before

After

97% ± 4% 103% ± 6% 86% ± 3% 445% ± 99% 628% ± 147%

97% ± 4% 103% ± 6% 86% ± 2% 446% ± 109% 613% ± 137%

97% ± 3% 101% ± 6% 85% ± 2% 452% ± 88% 595% ± 128%

97% ± 4% 102% ± 5% 86% ± 3% 445% ± 114% 588% ± 117%

After the intervention period the Pilates group showed an increase in middlesupport force of the left lower limb in the fastest walking-speed condition. It is worth emphasizing that the occurrence of referred pain to the left lower limb was more frequent in the Pilates group than in the no-Pilates group (Table 1). In addition, the Pilates group showed significantly decreased pain (visual analog pain scale and present pain intensity) after the intervention. It is known that middlesupport force is executed during the single-leg-stance phase, when the body is supported on the ground by only 1 limb. These data lead us to believe that the decrease in pain of these patients might have improved the weight discharge in the left lower limb during single-leg stance. The no-Pilates group did not present a significant change in these parameters after intervention period. In the physiotherapy management of patients with low back pain, attention has been focused on specific training of the muscles surrounding the lumbar spine,

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First peak force Second peak force Middle-support force Weight-acceptance rate Push-off rate

Parameter

After 103% ± 9% 109% ± 11% 66% ± 5% 970% ± 231% 976% ± 162%

Before

102% ± 8% 108% ± 11% 68% ± 4% 1073% ± 266% 963% ± 182%

Left Lower Limb 105% ± 7% 107% ± 10% 67% ± 4% 996% ± 243% 940% ± 163%

Before

103% ± 6% 107% ± 9% 68% ± 7% 1018% ± 399% 958% ± 138%

After

Right Lower Limb

Table 7  Vertical-Ground-Reaction-Force Parameters at Fastest Walking Speed in the No-Pilates Group Before and After the Intervention, Mean ± SD

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Table 8  Clinical Parameters Before and After the Intervention, Mean ± SD No-Pilates Group Before Visual analog pain scale Present pain intensity

6.1 ± 1.8 2.0 ± 0.7

Pilates Group

After

Before

After

4.9 ± 2.5 1.9 ± 0.9

5.9 ± 2.0 2.8 ± 1.5

3.0 ± 3.4* 1.1 ± 1.1*

*Significant difference within each group before and after the intervention.

whose primary role is considered to be to provide dynamic stability and segmental control to the spine.11 Earlier research has demonstrated that weakness and atrophy of the core muscles (multifidus and transversus abdominis) is usually present in patients with chronic low back pain.6–8 Furthermore, specific exercises to increase the tone and strength of these muscles can improve pain level10,16 and reduce low-back-pain recurrence.9 Our findings are in accordance with the literature, which suggests a mode of intervention of specific strength exercises for these muscles. The main aim of the study was to investigate whether individuals improved because of the intervention, and because individuals improve at different rates, a within-group analysis was performed to determine the significant differences after the period of intervention from baseline values. In conclusion, the findings from the current study indicate that pain distribution in people with low back problems has a different influence for the VGRF. When walking at preferred speed, those with referred leg pain decreased the amount of force imposed on their painful leg. In addition, Pilates can be beneficial for back-pain treatment through pain relief and improving weight discharge during gait execution. The mechanism for the improvement of weight discharge is believed to be through enhanced stability of the lumbar-spine segments and pain relief.

References 1. Salter RB. Distúrbios e Lesões do Sistema Musculoesquelético. 3rd ed. Rio de Janeiro, Brazil: Medsi; 2001.  2. Porto CC. Exame Clínico. 3rd ed. Rio de Janeiro, Brazil: Guanabara; 1996.  3. Hamill J, Knutzen KM. Bases Biomecânicas do Movimento Humano. São Paulo, Brazil: Manole; 1999.  4. Cholewicki J, McGill SM. Mechanical stability of the in vivo lumbar spine: implications for injury and chronic low back pain. Clin Biomech (Bristol, Avon). 1996;11(1):1– 15. 5. Kaigle AM, Holm SH, Hansson TH. Experimental instability in the lumbar spine. Spine. 1995;20(4):421–430. 6. Barker K, Shamley D, Jackson D. Changes in the cross-sectional area of multifidus and psoas in patients with unilateral back pain: the relationship to pain and disability. Spine. 2004;29(22):515–519.

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7. Hides JA, Stokes MJ, Saide M, et al. Evidence of lumbar multifidus muscle wasting ipsilateral to symptoms in patients with acute/subacute low back pain. Spine. 1994;19(2):165–172. 8. Ferreira PH, Ferreira ML, Hodges PW. Changes in recruitment of the abdominal muscles in people with low back pain: ultrasound measurement of muscle activity. Spine. 2004;29(22):2560–2566. 9. Hides JA, Jull GA, Richardson CA. Long-term effects of specific stabilizing exercises for first-episode low back pain. Spine. 2001;26(11):243–248. 10. O’Sullivan PB, Twomey LT, Allison GT. Evaluation of specific stabilizing exercises in the treatment of chronic low back pain with radiological diagnosis of spondylolysis or spondylolisthesis. Spine. 1997;22(24):2959–2967. 11. Richardson CA, Jull GA. Muscle control-pain control. what exercises would you prescribe? Man Ther. 1995;1:2–10. 12. Muscolino JE, Cipriani S. Pilates and the “powerhouse”—I. J Bodywork Mov Ther. 2004;8:15–24. 13. Craig C. Pilates com a bola. São Paulo, Brazil: Phorte; 2003.  14. Craig C. Abdominais com bola: uma abordagem de Pilates para fortalecer os músculos abdominais. São Paulo, Brazil: Phorte; 2004.  15. Blum CL. Chiropractic and Pilates therapy for the treatment of adult scoliosis. J Manipulative Physiol Ther. 2002;25(4):e3. 16. Gladwell V, Head S, Haggar M, et al. Does a program of Pilates improve chronic nonspecific low back pain? J Sport Rehabil. 2006;15:338–350. 17. Gabrieli APT, Vankoski S, Dias LS, et al. Análise laboratorial de marcha na mielomeningocele de nível lombar baixo e instabilidade unilateral de quadril. Acta Ortop Bras. 2004;12(2):1–12. 18. Hausdorff JM, Peng CK, Goldberger AL, et al. Gait unsteadiness and fall risk in two affective disorders: a preliminary study. BMC Psychiatry. 2004;4(39):1–7. 19. Hausdorff JM, Zemany L, Peng CK, et al. Maturation of gait dynamics: stride-to-stride variability and its temporal organization in children. J Appl Physiol. 1999;86(3):1040– 1047. 20. Keefe FJ, Hill RW. An objective approach to quantifying pain behaviour and gait patterns in low back pain patients. Pain. 1985;21:153–161. 21. Khodadadeh S, Eisenstein SM. Gait analysis of patients with low back pain before and after surgery. Spine. 1993;18(11):1451–1455. 22. Arendt-Nielsen L, Graven-Nielsen T, Svarrer H, Svensson P. The influence of low back pain on muscle activity and coordination during gait: a clinical and experimental study. Pain. 1996;64:231–240. 23. Selles RW, Wagenaar RC, Smit TH, et al. Disorders in trunk rotation during walking in patients with low back pain: a dynamical systems approach. Clin Biomech (Bristol, Avon). 2001;16:175–181. 24. Shelokov A, Haideri N, Roach J. Residual gait abnormalities in surgically treated spondylolisthesis. Spine. 1993;18(15):2201–2205. 25. Stebbins JA, Harrington ME, Giacomozzi C, et al. Assessment of sub-division of plantar pressure measurement in children. Gait Posture. 2005;22(4):372–376. 26. Lamoth CJC, Daffertshofer A, Meijer OG, et al. How do persons with chronic low back pain speed up and slow down? trunk-pelvis coordination and lumbar erector spinae activity during gait. Gait Posture. 2006;23:230–239. 27. Lee CE, Simmonds MJ, Etnyre BR, Morris GS. Influence of pain distribution on gait characteristics in patients with low back pain: part 1: vertical ground reaction force. Spine. 2007;32(12):1329–1336. 28. Melzack R. The short-form McGill Pain Questionnaire. Pain. 1987;30:191–197.

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29. Matsas A, Taylor N, McBurney H. Knee joint kinematics from familiarised treadmill walking can be generalized to overground walking in young unimpaired subjects. Gait Posture. 2000;11(1):46–53. 30. Amadio AC, Vecchia ED, Fernandes E, et al. Fundamentos biomecânicos para a análise do movimento. São Paulo, Brazil: Laboratory of Biomechanics/ EEFUSP; 1996.  31. Kistler Inc. Gaitway Operating Manual and Software Version 1.0x. Winterthur, Switzerland: Kistler; 1996.  32. Jacques SMC. Bioestatística: princípios e aplicações. Porto Alegre, Brazil: Artmed; 2003. 

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