Analysis of static postural balance and of intensity of musculoskeletal pains after the use of proprioceptive insoles by ostensive service militaries

ABSTRACT

To maintain the balance, the body uses visual, vestibular and proprioceptive systems, which send information to the central nervous system about the body’s conditions in order to stabilize it. This study evaluated the effect of proprioceptive insoles on static postural balance and musculoskeletal pains after two months of use, through a longitudinal analytical study with 15 healthy male soldiers with a mean age of 34±7.5 years. They were subjected to balance evaluation through the Medicapteurs® platform and by CNT protocol. There was no statistical difference for the deviations of the body and speed of the center of pressure. Plantar pressure had a statistically significant change for the left and the right feet, corresponding to p=0.0001 and p=0.0007, respectively. There was a reduction in the mean values of the pains in the knees, feet and heels and a significant decrease in lumbar spine pain, with p=0.0180. The static balance was not significantly altered with the use of proprioceptive insoles by the militaries; however, these insoles provided a better redistribution of plantar pressures and seem to attenuate the musculoskeletal pains of the lower extremities. Therefore, insoles can be considered as a prevention therapy against injuries for this group related to their work activity.

Keywords
Musculoskeletal Pain; Postural Balance; Orthosis; Pressure

RESUMO

Para a manutenção do equilíbrio, o organismo utiliza os sistemas visuais, vestibulares e proprioceptivos, que enviam informações para o sistema nervoso central acerca das condições do corpo com o objetivo de estabilizá-lo. Este estudo avaliou o efeito das palmilhas proprioceptivas sobre o equilíbrio postural estático e as dores musculoesqueléticas após dois meses de uso, por meio de uma pesquisa analítica longitudinal com 15 militares saudáveis do sexo masculino com média de idade de 34±7,5 anos. Eles foram submetidos à avaliação do equilíbrio por meio da plataforma Medicapteurs® e pelo protocolo CNT. Não houve diferença estatística para os desvios do corpo e velocidade do centro de pressão. A pressão plantar teve mudança estatisticamente significante para o pé esquerdo e o pé direito correspondendo a p=0,0001 e p=0,0007, respectivamente. Houve redução das médias de dores nos joelhos, pés e calcanhares e diminuição significativa da dor lombar, com p=0,0180. O equilíbrio estático não foi alterado significativamente com o uso das palmilhas proprioceptivas pelos militares, contudo elas proporcionaram melhor redistribuição das pressões plantares e parecem atenuar as dores musculoesqueléticas das extremidades inferiores. Por isso as palmilhas podem ser consideradas para esse grupo uma terapêutica de prevenção contra lesões relacionadas à sua atividade laboral.

Descritores
Dor Musculoesquelética; Equilíbrio Postural; Órtese; Pressão

RESUMEN

Para mantener el equilibrio el cuerpo utiliza los sistemas visuales, vestibulares y propioceptivos, que envían información al sistema nervioso central sobre las condiciones del cuerpo para estabilizarlo. Este estudio evaluó el efecto de las plantillas propioceptivas sobre el equilibrio postural estático y los dolores musculoesqueléticas después de dos meses de uso, a través de una investigación analítica longitudinal con 15 soldados sanos con una edad media de 34±7.5 años. Ellos fueron sometidos a evaluación de equilibrio a través de la plataforma Medicapteurs® y por el protocolo CNT. No hubo diferencia estadística para las desviaciones del cuerpo y para la velocidad del centro de presión. La presión plantar tuvo un cambio estadísticamente significativo para el pie izquierdo y el pie derecho correspondiente a p=0.0001 y p=0.0007, respectivamente. Hubo una reducción en las promedio de los dolores en las rodillas, pies y talones y una disminución significativa en el dolor lumbar, con p=0.0180. El equilibrio estático no se modificó significativamente con el uso de plantillas propioceptivas por los militares, sin embargo, proporcionaron una mejor redistribución de las presiones plantares y parecen ablandar los dolores musculoesqueléticas en las extremidades inferiores. Por lo tanto las plantillas pueden considerarse para ese grupo como una terapia de prevención contra lesiones relacionadas con su actividad laboral.

Palabras clave
Dolor Musculoesquelético; Balance Postural; Ortesis; Presión

INTRODUCTION

Proprioception influences postural modulation¹. Maintaining balance occurs by stimuli that keep the center of gravity at the support base², and the foot, with its mechanoreceptors, has properties for this control^3).

This function is evaluated by posturography, which checks the displacement of the pressure center (PC) ⁽⁴. Posturology uses this assessment to detect erect posture disorders, whose recommended treatment is the use of insoles⁵-orthotics manufactured with moldable material used inside shoes. Its principle of use is the prevention and therapy of standing posture, distributing the peak pressure and stimulating the feet sensory receptors⁶.

In the work environment, insoles can be used to decrease symptoms related to activities that adopt the same position⁷. Militarism is included in this context. In this work activity, there are a set of health-damaging factors, and the military’s complaints of pain are relevant⁸. Moreover, the design of military footwear and the attenuation of ground reaction forces do not seem to be effective⁹_.

Thus, this study analyzed the effect of the use of proprioceptive insoles on static balance and intensity of musculoskeletal pain in ostentatious service militaries, addressing overloads and possible repercussions on balance adjustments.

METHODOLOGY

This is an analytical, quantitative and longitudinal study with militaries from a battalion. The inclusion criteria were: being a military of ostensive patrolling, male, between 20 and 50 years old, who use boot or combat boot and feel musculoskeletal pain after prolonged orthostatic posture. Exclusion criteria: presence of neurological and cardiorespiratory sequelae; musculoskeletal lesions less than six months prior to the study; coordination, balance and ambulation changes; flat feet degrees II and III; cavus feet degrees II and III; valgus or varus knees; temporomandibular dysfunctions; visual changes; and structural scoliosis.

In balance assessment, the S-PLATE Medicapteurs® platform was used, measuring 610×580mm, with an active surface of 400×400mm of 1,600 resistive sensors, maximum pressure capacity of 100N, obtaining 100 images per second and frequency of 100Hz, in mode of postural acquisition. This procedure was performed pre-insole, immediate post-insole and late post-insole.

The participant positioned himself standing on the platform, in bipodalic support, barefoot, wearing light clothes, with heels apart forming an angle of 30°, arms in the extension of the body, stopped and with eye fixation at a point ahead for 30 seconds. For immediate evaluation, the same position was adopted with the addition of foot devices in the plantar region. After two months, the late reassessment was performed, following the same protocol and with the placement of the insole on the top of the platform, so that the participant stepped on it.

The parameters verified were: the mean range of PC displacement in the anteroposterior and latero-lateral in millimeters (mm), the mean velocity of PC in millimeters per second (mm/s) and mean plantar pressure in grams per square centimeter (g/cm²). In addition to examination on the platform, the CNT protocol was used¹⁰ for the prescription of the insole, in which the length of the upper limbs and the level of the iliac crests were observed, and then the test of the ascending thumbs is performed. The visual analog scale (VAS) was used to measure pain before and after two months of the insole use.

The insole used was the Comfort Standard model of the Podaly®, of thermoplastic resin TCSLIN with thermoglued EVAPOD cover. The insoles were composed of 3 mm, 6 mm and 9 mm wedges, retrocapital and infracapital bar, small and large hemidomes, intrametatarsal joint and medial longitudinal elevation selected according to each participant’s assessment.

The significance level was set at p<0.05. In the analyses of deviations, mean PC speed and mean plantar pressure of the feet, the Friedman’s test was used. For the evaluation of lumbar spine pain, the Wilcoxon signed-rank test was used, through bioest.5.0® software.

RESULTS

Table 1 shows the characterization of the sample group, composed of 15 militaries, predominantly young adults.

Table 1
Characterization of the sample profile

n=15	Age (years)	Weight (Kg)	Height (cm)
Mean	34.6	77.3	170.2
Standard deviation	7.5	9.4	4

Participants were instructed to use insoles at work for two months. At the end of this period the mean time of use was 28±10 days.

Regarding balance, deviations showed no statistically significant difference. However, a decrease in the mean values was observed, except in the latero-lateral deviation, when comparing the moments of pre-insole, immediate insole and late insole, as shown in Table 2.

Table 2
Mean±standard deviation for the latero-lateral and anteroposterior dislocations in millimeters and mean speed of oscillations in millimeters per second in static posture between study moments

	Pre-insole	Immediate insole	Late insole	p - value*
latero-lateral deviation	0.96±0.33	0.76±0.23	1.01±0.69	0.0730
Anteroposterior deviation	1.23±0.60	1.12±0.57	1.13±0.47	0.6271
Average speed	1.43±0.43	1.30±0.42	1.34±0.43	0.4419

• *Statistical test: Friedman’s test, p<0.05.

On the other hand, the values of the mean plantar pressure of the left foot and the right foot had an evident reduction, with statistical significance, as shown in Table 3.

Table 3
Mean±standard deviation of mean plantar pressure in grams per square centimeter in the right foot and left foot in static posture between study moments

	Pre-insole	Immediate insole	Late insole	P - value*
Left foot	240.73±32.73	228.40±24.60	215.13±29.49	0.0001*
Right foot	244.07±31.68	221.47±22.13	217.13±21.82	0.0007*

• *Statistical test: Friedman’s test, p<0.05.

Table 4 shows musculoskeletal pain before and after late insole. It is observed that the most cited areas are the feet and lumbar spine. There is also a decrease in the average pain values in all anatomic regions.

Table 4
Absolute, mean and standard deviation of intensity of pre-insole and post-insole musculoskeletal pain, according to the anatomical region.

Anatomical region	n	Pre-insole pain		After late insole pain
		Mean	SD	Mean	SD
Lumbar spine	10	4.7	1.7	2.5	1.27
Right knee	2	6	1.41	1.5	2.12
Left knee	2	7	0	3.5	4.95
Right foot	4	5.5	3	1.75	0.96
Left foot	5	5.6	2.6	1.8	0.84
Right heel	2	4.5	0.71	3	0

Pain in the lumbar spine was analyzed by the Wilcoxon signed-rank test, with a statistically significant difference of p=0.0180, since it was the most reported pain.

DISCUSSION

The effects of the prescription and the types of plantar arches¹¹⁾ must be evaluated to recommend an insole. It is known that the militaries are liable to injury. Moreover, the military shoe and insoles do not consider the types of feet¹².

A decrease in the means is observed when comparing the values of oscillations and mean velocity, except for late latero-lateral deviation, without, however, statistically significant difference. These results show that in healthy adults imbalances are discrete¹³. On the other hand, the increase in late latero-lateral deviation may be related to the adaptive process generated by manipulation in plantar support.

Studies show that plant reliefs generate changes in body stabilization¹⁴, which legitimizes the decrease in oscillations and the speed of the pressure center seen in the analyses of this study. Similar to Mantovani et al. ⁽¹⁵, in which the values of the mean anteroposterior oscillation before, during and after the use of insoles showed a reduction in the initial values, even without significant difference.

Ahmadi et al. ⁽¹⁶ also did not report significant difference in balance after insertion of lateral wedges in 18 patients with medial osteoarthritis in the knees. In Hemmati et al. ⁽¹⁷, orthotics did not present negative effects on foot balance and therefore are not a threat to the balance. Studies in which there are balance dysfunctions are needed¹⁸. Evidence shows significant reduction in body balance in children with cerebral palsy after insole use¹⁹.

These orthotics are a precautionary means in people with normal balance oscillations. There are studies suggesting that they can reduce stress injuries in the femoral and tibial region in militaries²⁰.

In this study, plantar pressure showed statistical difference, similar to studies that agree that insoles reduce pressures^{21), (22}. These data disagree with Almeida et al. ⁽²³, in which there was no significant difference.

It is difficult to confront the data²³ due to the different materials of insoles in both aforementioned studies. Despite these divergences, it can be inferred that, in general, custom insoles have a better mechanism of attenuation of loads, since they consider individual characteristics of the feet. This breakdown of plant loads is useful, reducing the risk of lesions in lower extremities²⁴.

Regarding musculoskeletal pain, there is a decrease in means and significant reduction for lumbar pain. The military shoe can cause injuries due to its shape and material, which do not respect the individual characteristics²⁵.

Ferreira et al. ⁽²² reported significant reduction in painful sensation in the lumbar spine, legs, feet and left knee after two months of orthosis use. In Almeida et al. ⁽²³, a decrease in levels of pain was observed in the feet and lumbar spine. However, Chuter et al. ⁽²⁶ have not shown sufficient evidence that insoles can impact on lumbar spine pain. Cambron et al. ⁽²⁷⁾ observed a significant reduction after six weeks of use. These results indicate that the treatment of back pain by means of insole requires further studies²⁸.

As limitations of this study we can cite the small sample and the differences in the frequency of insole use by the participants. Moreover, all militaries were allocated in a single group, although the different types of feet were considered in the analysis. This is a limitation because the degree of contact of the foot with the insole may vary depending on the type of arch, leading to different levels of stimulation, adaptation periods and correction of asymmetries. Furthermore, the study population was healthy, so the results were discrete. The implications of the insole could be more evident in groups of militaries with balance deficits.

CONCLUSION

Static balance has not been significantly altered by the use of proprioceptive insoles by healthy militaries. However, they provided attenuation and better distribution of plantar pressures and seem to influence musculoskeletal pain in the lower extremities. Therefore, a disease prevention therapy related to their work activity is recommended for this group.

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• 5
  Study conducted in the Manual Therapy sector of the Neuroativar Clinic - Santarém (PA), Brazil.
• 6
  Financing source: nothing to declare
• 8
  Approved by the Comitê de Ética e Pesquisa da Universidade do Estado do Pará Campus XII under opinion No. 1,963,489 and CAAE: 65155617.2.0000.5168.

Publication Dates

• Publication in this collection
  06 Apr 2020
• Date of issue
  Jan-Mar 2020

History

• Received
  08 May 2018
• Accepted
  05 Feb 2020