Sensory Motor Stimulation

Vladimír Janda

Marie Vávrová

Alena Herbenová

Michaela Veverkova

Introduction

Therapeutic approaches have been continuously changed with respect to our knowledge and progress of physiology. The original approach considered the motor system as an effector only and did not understand its role with the afferent system as one functional unit. The result of this approach was the idea that motor performance is a result of isolated and separate, although coordinated, activation of individual muscles. The main concern of these techniques was activation of individual muscles or muscle groups in the hope that the new motor pattern will be developed automatically. Examples of such thinking are exercises prescribed according to muscle testing or the progressive resistance exercise program. The next evolution in thinking about exercise accepted that a movement cannot be accomplished without coordination of the afferent pathways and centers; thus, the realization that the motor system and the afferent system were closely linked.

Sensory Motor Stimulation Background

Therapeutic Approaches

Kabat developed and introduced into practice the concept of activation of afferent pathways as an approach to movement reeducation.¹ In therapy, this concept is the basis of the proprioceptive neuromuscular facilitation (PNF) technique. This approach, and similarly others developed during the past few decades, such as that of Temple Fay, Bobaths, Vojta, Rood, to mention only some of the most important ones, systematically stresses muscle coordination and the importance of proprioceptive information. At present, it is understood that the afferent system does not have only an informative role, but that it participates substantially in motor programming and motor system regulation. Therefore, proprioceptive stimulation is stressed more and more.

The term proprioception was used for the first time by Sherrington to describe the sense of position, posture, and movement.² Over time this term has been used in a much broader way, and today, although not quite correctly, it is used for nearly the entire afferent system.

It is understood today that splitting the function and/or dysfunction of the myo-osteo-articular system from the central regulatory nervous mechanisms is wrong. Both parts function as one inseparable functional unit and cannot be separated. Thus, any lesion or impaired function of any part of the peripheral motor system leads to adaptative mechanisms in the central nervous system and vice versa.

Probably the first one who, from the clinical point of view, noticed the relation between the lesion (injury) of the foot joints and incoordinated muscle function of the lower leg was Kurtz.³ However, aside from the fundamental experimental works of Wyke and Skoglund, in clinics it was Freeman and coworkers who systematically considered some aspects of joint traumatology and the importance of impaired afference in the genesis of an unstable ankle joint.⁴^,⁵^,⁶^,⁷^,⁸ Freeman was also the first one who introduced in non-neurological cases a detailed evaluation of coordination and stressed the importance of muscle inhibition as an integral part of the clinical picture.⁵ Since the first paper of Freeman, the interest in this problem has increased.⁴ One of the most extensive works is the book of Hérveou and Messean, Technique de Reeducation et d’ Education Proprioceptive.⁹

In our clinic we started to work out our program, based to some extent on the papers mentioned, in 1970. To avoid problems in terminology and/or confusion, we have named our technique “sensory motor stimulation” (SMS) in the hope that this term will stress the unity between the afferent and efferent systems without implicating any specific structure or function and will not lead to confusion with PNF.

Basic Concepts of Motor Learning

The principle of SMS is based on the concept of two stages of motor learning.¹⁰ The first stage can be characterized as an attempt to achieve a new movement performance and to work out the basic motor program. In this process, the brain cortex (predominantly the frontal and parietal) is strongly involved. This type of motor regulation has some advantages as well as disadvantages. It enables the individual to achieve new skills; however, as it passes several synapses, it is rather slow and because of the necessary conscious participation of the cortex it is tiring. Therefore, the brain tries to minimize the pathways and to simplify the regulatory circuits. This mechanism has been named as the second stage of motor learning. It enables a reduction in cortical participation and is thus, less tiring and much faster. However, if such a motor program has been fixed once, it is very difficult, if not impossible, to change it. Therefore, in motor reeducation the attempt has to be made to achieve a quality
of movement patterns that are as close to the normal as possible.

To prevent injury, and microinjury in particular, fast reflex muscle contraction is needed to protect the joints. The second stage of motor learning enables such a faster response, which in fact may play a decisive role in prevention. It has been shown that it is possible to accelerate by increased proprioceptive flow and balance exercises the muscle contraction by approximately 2-fold.¹¹ In principle, in SMS an attempt is made to stimulate the proprioceptive system and those circuits and pathways that play an important role in the regulation of equilibrium and posture.

From the afference point of view, excluding the skin exteroceptors, three areas have the main proprioceptive influence. These are the receptors from the sole of the foot (Freeman), from the neck muscles (Abrahams), and the sacroiliac area (Hinoki).⁴^,¹²^,¹³

Afference from the sole receptors can be increased in different ways, for example, by stimulation of the skin receptors or, more effectively, by active contraction of the foot muscles, with the emphasis on activity of the intrinsic muscles.

Clinical experience has revealed that activation in particular of the intrinsic muscles of the foot with only tonic activation of the toe muscles is most effective. Therefore, the “foot fist,” as recommended for activation of proprioceptors by Ihara and Nakayama, is not used in this method.¹⁴

The deep neck muscles contain, in comparison with other striated muscles, many more proprioceptors.¹² Abrahams has shown that these muscles should be considered as muscles for maintaining posture and equilibrium rather than muscles for producing dynamic movement. It should be mentioned that the deep tonic neck reflexes are the result of muscle activation and not of the neck joints, as it was mistakenly described originally.

The area of the sacrum has been, in clinical practice, recognized as an important area to control posture and equilibrium only recently. The observation of Hinoki confirms this.¹³ However, at present it is not possible to differentiate whether it is the sacrum itself and its position or whether it is the sacroiliac joints that play the decisive role.

A special role has been recognized for the cerebellum and the whole spino-vestibulo-cerebellar regulatory circuit.

Sensory Motor Devices and Aids

In principle, various balance exercises are used. The equipment used is simple and inexpensive. The principles are not new and were introduced by Bobath and Bobath¹⁵ for motor reeducation of children with cerebral palsy. However, the application to chronic back pain patients is rather new and has been introduced only recently.

Figure 21.1 Rocker board.

There are many types of exercise aids—from wobble and rocker boards, balance shoes, various types of twisters and trampolines, and the Fitter. Wobble and rocker boards are made preferably from wood and not from plastic material, because wood stimulates the receptors more (Figs. 21.1 and 21.2). The average dimensions for the rocker board are: length, 35 cm; width, 25 cm; and height, 15 cm.¹⁶ The radius of the wobble board is, on average, 35 cm and the height is 15 cm. Exercises on the rocker board are easier; therefore, it is advisable to start with it.

The size of the balance shoes depends on the size of the foot. The sandals have to have a firm, not flexible, sole, with the modeled sole and the metatarsal support, because these help to configure the small foot.
There should be just one strap over the forefoot and the heel should remain free, again to help to activate the muscles of the foot. The hemispheres are made from solid rubber, 5 to 7 cm in diameter, and placed in the center of the sole (Fig. 21.3).

Figure 21.2 Wobble board.

Figure 21.3 Balance shoes.

The twister enables activation of the trunk and buttock muscles. When exercised in front of a mirror, one can visualize any asymmetry in muscle strength and/or asymmetrically performed exercise. We prefer to use a flat twister 40 cm in diameter.

The Fitter (similar to the twister), strictly speaking, is not a device for proprioceptive training; however, it substantially helps to improve coordination. There are several devices with a similar function on the market. We use one that was developed by Fitter International from Canada (Fig. 21.4).

A mini trampoline is an excellent device to stimulate the proprioceptors of the whole body (Fig. 21.5). Unfortunately, the mostly used trampolines do not have sufficiently resilient material. The stimulatory effect is thus reduced. Springs of 15 to 18 cm in length provide a suitably unstable base; springs of less than 7 cm are of little proprioceptive value, although they decrease the compression of weight-bearing.

Figure 21.4 The Fitter.

Figure 21.5 Mini trampoline.

Exercise on gymnastic balls (mostly 65-85 cm in diameter) is very efficient for kinesthetic stimulation and balance training.

Indications for SMS

SMS can be beneficially used as a part of any exercise program because it helps to improve muscle coordination and motor programming or regulation, and it increases the speed of activation of a muscle. It was used originally to improve the unstable ankle after an injury; however, it can be used for a variety of conditions (Table 21.1). Chronic back pain syndromes are one of the most important indications. Better control of the trunk, improved activation of the gluteal muscles, and thus better stability of the pelvis is achieved. There is a broad indication for sensory defects of neurological origin. Used carefully (to avoid injury), the method can help to compensate proprioceptive loss in aged subjects and thus help to prevent falls. Balance deficits have been correlated with an increased incidence of falls, and
balance training has been shown to be an effective preventive intervention. However, this technique cannot be recommended for patients with acute pain syndromes.

Table 21.1 Indications for Sensory Motor Stimulation

Posttraumatic, postoperative
Chronic back and neck pain
Faulty posture connected with respiratory dysfunction
Hypermobility and instability in general (unstable ankle, knee, pelvis, spine)
Less severe forms of idiopathic scoliosis
Postpartum muscle imbalance
Certain neurological conditions
Prevention of falls in senior population
Maintenance of general fitness

Methodology

Overview of Sensory Motor Training

In this chapter the main principles of sensorimotor training are described. A more detailed description was published in Czech¹⁷ and can be seen in Czech and English on videotape.¹⁸^,¹⁹

One of the most important advantages of this program is that it helps to improve not only the muscle imbalance but also, in particular, the most important motor activities such as standing, that is, posture and gait. At the same time, the control of posture in daily activities, including those related to work and sport, is facilitated and improved automatically. Therefore, exercises performed in the upright position are the most important.

As a general rule—from a motor control perspective—a program to normalize relevant dysfunction in the periphery should be initiated before beginning the SMS exercises. This is because any pathological or unwanted proprioceptive information from the periphery results in functional, adaptative processes of the whole central nervous system. Therefore, attention should be paid first to the skin, fasciae, muscles, and joints, and their adjacent structures. Also, trigger points, whether active or latent, should be treated before beginning sensorimotor training.

Muscle imbalance, which is always present at least to some degree, should be improved first. This is particularly true in the case of severe muscle imbalance. The preparatory exercises include stretching of the tight muscles first, followed by strengthening the weak ones. The emphasis is placed on the specific patterns of coordination important for correct posture in standing.

Table 21.2 Sensory Motor Stimulation (SMS) Rules

The exercise program in the upright position follows several rules:

Correction is started from distal areas and gradually continued proximally. Therefore, activation of the foot (feet) comes first, then correction of the position of the knees, then that of the pelvis, and finally that of the head, neck, and shoulders.
Exercises are performed barefoot because this increases both exteroceptive and proprioceptive input and enables the therapist to pay attention to better control. Last but not least, it helps to decrease the danger of injury.
Exercise should by no means provoke pain and should not lead to either physical (somatic) or mental (psychic) fatigue.
From the very beginning, special attention is paid to the awareness of posture (particularly feet, pelvis, and head).
All exercises should be first trained on a firm surface, then on balance devices.
The number of repetitions of each exercise should be between 10 and 20 in a typical treatment session. The more difficult exercises are repeated only five to six times.
Hold times for most of the exercises is 5-10 seconds.
The duration of a typical SMS training session varies. Balance shoe walking takes approximately 2 minutes in one treatment session, whereas other aspects of the routine can be longer (20-30 minutes in one treatment session).

To increase the proprioceptive flow, special attention is paid to activation of the intrinsic foot muscles, the locking mechanism of the knee, stabilization of the pelvis, and, last but not least, the position of the head, neck, and shoulder girdle. Table 21.2 outlines the basic rules for administering SMS.

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