Influence of pilates exercises on soil stabilization in lumbar muscles in older adults

The practice of regular physical activity is recognized as a strong ally of active aging, healthy, or successful, whose hallmark is the independent and effective performance of activities of daily living. The Pilates Method (MP) has emerged as a good alternative physical activity in older adults with the main objective of strengthening and stretching the muscles simultaneously, raising body awareness. The aim of this study was to analyze the effects of MP on the strength and conductivity of the electrical stimulation of the lumbar paraspinal muscles as well as muscle contraction transversus abdominis (TrA) in older women before and after performing Pilates exercises on the ground. The instruments used were surface electromyography, force transducer and pressure biofeedback unit. Participants were aged 13, who underwent 12 sessions of Pilates exercises on the ground with an average duration of 50 minutes, are reviewed at the end of the intervention protocol. The participants had increased strength and electrical activation of the lumbar paraspinal muscles, as well as increased ability to contract the transversus abdominis muscle.  Based on the results obtained we can conclude that there was a significant improvement of strength and electrical conductivity of the stabilizing muscles of the lumbar voluntary and therefore training with MP positively influenced this musculature.


INTRODUCTION
With increased longevity, the number of older adults has grown substantially.Brazil is assuming a demographic profile of ageing population, indicating changes in the population age structure 1 .
One indicator that shows this process is the ageing index.Between 2035 and 2040, the number of elderly people (aged 65 and over) may reach 18% more than the number of children (0 to 14 years old) and, in 2050, it may represent 22.71% of total population 2 .
By definition, aging is the sum of all processes (alterations and adaptation) that occur along the years in the human body 3 .The main alterations include reduced muscle strength, which limits daily activities and reduces the functional interdependence of the elderly people¹.This fact is particularly relevant for women, who have longer life expectancy than men, reduced functional reserve and greater reduction of muscle strength 4 .
The maintenance of interdependence for activities of daily living (ADL) is a predictive factor for successful ageing 5 .Thus, the therapy of physical exercises for the elderly people has been proposed to prevent and treat disabling events, chronic diseases and risk factors 6 .Pilates is a physical fitness system that combines strength and flexibility and, with the benefits proposed for better muscle control, it may be an effective method for the elderly people 7 .
The purpose of the Pilates method is to strengthen muscles located in the center of the body (abdominal and paravertebral muscles), referred to by Joseph Pilates (who developed the method) as the powerhouse.He combined improvements in motor activity, body stability and movement with better flexibility of these muscles 8 .
Then, the Pilates method can have a new focus, acting as a therapy tool to prevent and treat geriatric disorders, which, associated with the restricted number of studies in the area, justify studies that evaluate the Pilates method effect on elderly people.The purpose of this study was to analyze the influence of the Pilates method on the strength and conductibility of electrical stimulation of paravertebral muscles and the contraction of transverse abdominal (TVA)musclein elderly women before and after performing Pilates exercises on the ground.

Study design
This is a quantitative, comparative descriptive study.Data were collected at the primary care clinic of the sector of Physiotherapy at the Hospital Getúlio Vargas, in the city of Teresina-Piauí, from April to June 2013.All participants were informed of the study procedures and signed an Informed Consent Term before they were submitted to the intervention protocol, which was approved by the

Sampling
The participants were submitted to an interview to collect data about their practice of physical activity, diseases, use of medication and family history.The sample had 13 elderly women.The inclusion criteria were: women between 60 and 80 years of age, who agreed to participate spontaneously in the study, by signing an Informed Consent Term and that practiced physical activity regularly(three or more times a week, for at least 30 minutes).The exclusion criteria were: presence of any restriction to practice the proposed activities, comprehension deficit and more than two absences in the scheduled visits.

Evaluation protocol
An initial evaluation was conducted, and personal data were collected from the participants; then, the electrical strength and stimulation of paravertebral muscles was evaluated and the TVA muscle contraction was indirectly measured.
A force transducer (0-200 kg range) produced by EMG System do Brazil LTDA evaluated the paravertebral muscle strength evaluation, connected to the electromyography system.
The electromyographic analysis of paravertebral muscles used an 8-channel surface electromyograph produced by EMG System do Brazil (São José dos Campos, SP, Brazil) with signal acquisition and processing software, calibrated before this study was conducted.The sampling frequency was 2000 Hz, expansion of 1,000 times, high-pass 20Hz filter and low-pass 500Hz filter and 12-bit analog converter.The bipolar technique used Kendall surface electrodes (Meditrace -100; Ag/AgCl; 2.2cm diameter) for signal capture, and all procedures in the protocol of SENIAM (Surface Electromyography for Non-Invasive Assessment of Muscles) 9 project were rigorously observed.The electromyographic signal was statically collected.
The electrodes were bilaterally placed at level L5 and aligned in parallel between the line of posterior superior iliac spines and the interspinous space of L1 and L2, placed on the muscular venter, in parallel with the muscular fibers, keeping 2cm between them.For comparison, the EMG signals were normalized, based on the maximum isometric voluntary contraction (MIVC).
The participants remained in the sitting position, at 90º hip flexion.In this position, they were instructed to stretch the trunk against the load cell resistance for ten seconds when they heard the sound stimulation, when the signals were captured.
The indirect measurement of the TVA muscle contraction was conducted using a Stabilizer Pressure Biofeedback unit.During the tests, with participants in ventral decubitus (VD), the inflatable bag was placed in the space immediately above the anterior superior iliac spines, under the umbilical scar.
Before starting the contraction, the pressure bag was insufflated to 70mmHg with closed valve.The participants were instructed to breathe in and out some times especially using the abdominal region.The bag pressure was then again adjusted to 70mmHg.Three contractions of the TVA muscle were requested with the following command: "Force the abdomen upwards and inside, without moving the spinal column and pelvis".These contractions were made for at least ten seconds, with 1-minute interval between every contraction, measured with a timer.After that, the average of three values was calculated.
The classification adopted for the evaluation of the values found with the Stabilizer Pressure Biofeedback unit was that proposed by Richardson et al 10 : 70mmHg corresponding to 0mmHg -no alteration; 70-66mmHg: 0 to -4mmHg -insufficient contraction of the TVA muscle; 66-60mmHg: -4 to -10mmHg -excellent performance; above 70mmHg means full muscle contraction.
The protocol comprised Pilates exercises on the ground; stretching and exercises were performed for the Upper Limbs (UL), trunk and Lower Limbs (LL), with repetitions and strength increasing along the exercise weeks, using a Swiss ball, thera-band and flex ring.Twelve sessions of the Pilates method were performed, three times a week; each session lasted 50 minutes on average.After the protocol was concluded, the participants were revaluated.
Box 1. Protocol comprised of basic exercises adopted in the study.

Statistical Analysis
Data were evaluated first through the Shapiro-Wilk test to assess normality, and then, using the Student's t-test for parametric data and the Wilcoxon t-test for non-parametric data.The level of statistical significance considered in this study was 95% (p<0.05) using Bioestat 5.0 (application).

RESULTS
Table 1 shows the anthropometric data of the participants.
Pilates exercises on soil Pinheiro et al.In terms of laterality, the comparison of left and right muscles of the vertebral column did not show any statistically significant difference.
Table 2 show the mean values of the TVA muscle activation, before and after the intervention.

DISCUSSION
This study analyzed a homogeneous population, following the preestablished criteria, and which remaining the same until the end of the study, allowing to compare pre-and post-intervention moments.Sarcopenia, defined as a slow, progressive and apparently inevitable process of loss of muscle mass and strength, is one of the most important physiological changes associated with ageing 11 .This strength is estimated to reduce, on average, 15% every decade after the age of 50 and 30% after the age of 70 12 .
Specifically in women, one of the factors that contribute to sarcopenia development and progression is the reduction of estrogens associated with menopause.The female sex steroids possibly have anabolic effects on muscle through tissue conversion in testosterone 13 .
Inactivity, common in this population, favors physical dependence, leading to inability to perform ADL 14 .Evidences suggest that an exercise program prevents and/or minimizes the deleterious effects of ageing 15 .
One of the purposes of prescribing physical exercises to elderly people is to increase and/or keep muscle strength, acting against sarcopenia 16 .Resistance exercises and innovative methods, like Pilates, which emphasizes principles such as strengthening of abdominal and paravertebral muscles while keeping good posture, body alignment and breathing, are today in perspective in exercise programs 17 .
Pilates is characterized by efficient movements of abdominal, gluteal and paravertebral muscles 18 , which explains the considerable improvement in the participants' ability to contract these muscles, as the protocol adopted in this study comprised mainly basic exercises of a program to strengthen these muscles.
One of the results observed was increased paravertebral muscle strength.The mechanisms involved in such increase, in elderly people, are still not fully explained, but can be attributed to neural adaptations and/or muscle hypertrophy.Thus, a possible explanation for increased strength might have been the increased neuromuscular activation, also observed in the study.
Considering that, to perform muscle strength activities, the neuromuscular activation should occur first, the results are considered consistent, as with the increased number of muscular fibers activated, due to increased electrical activity, the consequence is increased muscle strength observed in the study.
Other studies conducted with the Pilates method presented similar results.Sekendiz et al 19 analyzed the effects of Pilates exercises on the ground on trunk muscle strength and flexibility of21 sedentary adult women, whose mean age was 30 years.The authors presented significant improvement in both variables (strength and flexibility).Kolyniak et al 20 evaluated the effects of Pilates exercises on the function of trunk extensors in 20 people (16 woman, mean age: 34.06 years; four men, mean age: 33.5 years).The study presented significant result: 25% increase in strength peak of the extensor muscles.Another study that confirmed these results was the one conducted by Kawanishi et al 17 , which presented positive effects of Pilates training on the reduction of pain symptoms and improvement of lumbar flexibility and strength in 12 individuals with chronic low back pain (6 women and 6 men, mean age: 33 years).
The increased strength in paravertebral muscles is very relevant, as these muscles ensure the correct position of upright trunk and act as synergists for the movements of body segments.When the performance of these muscles is poor, the spinal column shows instability.That leads to loose ligaments, alteration to muscle control, pain and muscle fatigue 21 .
Low resistance to fatigue of paravertebral muscles, defined as reduced ability of the neuromuscular system to produce strength, is common in patients with chronic low back pain and such fatigue results in abnormal movements of the trunk and loss of muscle control that can lead to micro lesion of ligaments and intervertebral discs 21 ; thus, justifying the importance of strengthening these muscles.
In terms of laterality, the comparison of left and right muscles of the lumbar spine did not show any statistically significant difference, in agreement with the study conducted by Gonçalves & Barbosa 22 .
Regarding the TVA muscle, its activation was obtained by using a Stabilizer Pressure Biofeedback unit, an instrument commonly used in clinical practice and studies that evaluate the TVA muscle activation ability, with good level of reliability and accuracy.This instrument has already been associated with imaging exams and electromyography, considered gold standards in the analysis of TVA behavior 23 .
Richardson et al 10 state that the usual answer to the records of Stabilizer Pressure Biofeedback unit is pressure reduction between -4 and -10mmHg, that is, in actual values of 66 to 60mmHg.Hodges et al 24 report that the ideal depression of the abdominal wall should be -5.82mmHg or above.
Table 2 shows a significant increase was observed in the TVA muscle contraction (p< 0.001).According to the classification proposed by Richardson et al 10 , the participants that had insufficient contraction (-1.66mmHg) before, present now excellent performance (-9.33mmHg), after practicing the proposed exercises.
The increase in TVA muscle contraction ability can be explained by the type of breathing adopted in the Pilates method.The Pilates exercises use inhaling as relaxation and preparation for the movement, while exhaling is used for abdominal practice, by activating the accessory muscles of inspiration, such as: rectus abdominis muscle, transverse abdominal muscle and oblique muscles 20 .
Kloubec 25 , in his study with 25 patients, reported that the Pilates method promoted statistically significant increases in the abdominal muscle strength of participants, in agreement with the results obtained in this study.
The increased ability of the TVA muscle contraction observed in this study is very relevant, due to the importance of these muscles to keep the lumbar spine integrity.Studies show that individuals with chronic low back pain present deep abdominal muscle mal function, especially the TVA muscle.
Ramos et al 23 evaluated the TVA muscle activation ability of individuals with and without unspecific chronic low back pain.The results showed that individuals with chronic low back pain presented insufficient TVA muscle activation (-0.3mmHg), while individuals without chronic low back pain presented almost excellent contraction values (-3.6mmHg), indicating more efficient activation in healthy individuals.
The Pilates method involves muscle exercise of low-impact contraction, intensely strengthening lumbar stabilization muscles 26 , in agreement with the results found, as it increased the strength of abdominal muscle and trunk extensor.
The practice of this method, by strengthening the powerhouse muscles, especially the deep stabilization muscles (transverse abdominal muscle), improves the dynamic balance of elderly people, providing stability.On the other hand, the inefficiency of these muscles, associated with weakening, leads to unstable trunk, which may increase the stress of intervertebral articulations, favoring degeneration in this segments and, consequently, the development of pathologies 6 .

CONCLUSION
Based on the results of this study, after twelve sessions with the Pilates method, a significant improvement of lumbar stabilization muscle strength was observed in the participants and, therefore, the training brought positive effects to these muscles.Although the results are positive, they are consistent with the small group studied.Thus, new random studies are required with larger sample sizes, longer intervention period, and including male elderly people, investigating the effects of this activity on elderly population.The Pilates exercises can be practiced by elderly people between 60 and 80 years old, and, besides involving low cost of implementation, the Pilates method can be consolidated as a new therapy strategy for a group that tends to keep growing in the near future.
one foot at a time 5Bridging, releasing one foot at a time 10

Figure 1 .
Figure 1.Comparison of paravertebral muscle strength before and after Pilates exercises on the ground.Teresina, Piauí, 2013.

Figure 2 .
Figure 2. Comparison of the electrical activity of left and right paravertebral muscles before and after the Pilates exercises on the ground.Teresina, Piauí, 2013.