Metabolic diseases related to dietary habits

Almost all our daily activities are performed under the influence of gravity.

Most of our effort and time is spent in reacting to the effects of gravity upon the body. Protective responses in maintaining balance are considered to have survival value by preventing us from falling as well as enabling us to maintain our sense of verticality.

Posture is the term used to describe a position of the human body. The human body is capable of several postures like lying, sitting, crawling, and standing.

In all these postures the body needs to be stable in order to do its activities.

Stability depends on whether the base and the position of the centre and line of gravity are either balanced in equilibrium or not. Balance and posture are interrelated.

Balance is maintained at a subconscious level, by integrating sensory inputs from the eyes, the vestibular apparatus, and the proprioceptors and super imposing them on a basic amalgam of posture and postural reflexes in the normal individual. While retraining a patient’s balance he is given stimuli to which he must react. This is more important than his making a conscious effort to maintain equilibrium.

There are two types of balance—static balance and dynamic balance. Both of these are needed for normal activities. It need not be thought that balance training need be done only for neurological deficit. On the contrary balance retraining is an integral part of all gait training exercises or rehabilitation programs.

Static Balance

Static balance is the rigid stability of one part of the body on another. Even a person standing immobile is contracting his muscles in an isometric fashion.

There is also contraction of muscles equally. As a general principle balance

is developed progressively by moving from the more stable to the lesser stable position, for example from forearm support prone lying to sitting without support.

In the development of a child head control is the first to develop. This reinforces the fact that stability and control of the head should be given priority as it is needed in all positions. Later, the extensors of the neck and back and also spinal stabilizers can be stimulated to reinforce muscle contraction elsewhere, e.g. righting reactions, which are involuntary movement responses to stimuli, serving to maintain the alignment of the head and body in its normal upright posture.

Dynamic Balance

The body, unless it is fully supported and relaxed, like lying down, is in a constant state of adjustment to maintain its posture and its equilibrium. The force of gravity acts on it threatening to destabilize it. Maintaining balance means having the centre of gravity of the body within the base of support, i.e. with the trunk aligned over the feet. A soldier at attention might appear completely still, but he continuously transfers his weight and oscillates trying to maintain his center of gravity within his base. He is able to do this because of his sense of proprioception which provides feedback on the status of the body internally whether the body is moving and if so how, and whether the various parts of the body are located properly in relation to each other.

Equilibrium Reactions

These are involuntary automatic responses to a disturbance or destabilization in the structure of the body that serves to maintain or regain balance during posture and movement. These balance reactions may occur by an adjustment in tone or an adjustment in posture

Method of Stimulation

For balance to improve in a position, the patient must be assisted to assume that position. Man’s body axis is vertical, and it is in the vertical position, that he needs the ability to withstand the effects of gravity. Analysis of balance reactions and body alignment in responses to shifts in weight will identify the deficient areas, which require specific stimulation. For example, if a person is pushed to his right, he moves his head and trunk in the opposite direction with corresponding compensatory reactions of the pelvis and lower limbs to bring his center of gravity within his base of support. Any one or all of the components of balance may be missing and must be stimulated by the therapist.

Alternate tapping stimulates balance in antigravity positions. Gentle taps are applied alternately to the upper trunk with the body in normal alignment.

The effect should be to displace the patient slightly off balance in alternate

directions, which will stimulate the necessary adjustments. It must be stressed that the displacement should be small so as to stimulate only fine adjustments.

Maintenance of Position

The patient is instructed to maintain the position, for example, prone kneeling, sitting or standing against the therapist’s tapping technique to displace him backwards, forwards and laterally.

The use of a moving support is valuable in some positions. Objects used include balance boards, rolls which are made of a cardboard tube, and therapeutic balls. If balance reactions fail, protective extension (parachute reflex) of the arms is one of the most important reactions.

In general, movement for balance is stimulated smoothly and steadily, in a small range initially, gradually increasing the range as the patient gains more control. Any position can be made more stable by using pressure and approximation and by providing the patient a wider base by giving more than one fixed point of stability. Too much emphasis on stability would prevent the patient from moving or trying to move. On the other hand, too much stimulation of movement might result in loss of balance and the confidence to regain it. The use of weights worn by the patient on the trunk or lower limbs is sometimes suggested as a means of improving movement control.

Balance Boards consist of a platform, which may be either rectangular or circular, resting on a hemispherical base. They re-educate balance and increase strength of the muscles of the leg. The patient is given various positions on the balance board and he should learn to maintain his balance while sitting, kneeling or standing on it, while it is displaced in different directions. The Bobath ball is very useful in this training.

GAIT

Gait or human locomotion, may be described as a translatory progression of the body as a whole, produced by coordinated movements of body segments.

It is the forward progression of the center of gravity (a point in front of the 2nd sacral vertebral body) of the body, based on the reciprocal movements of the lower extremities. Man is the only animal among vertebrates, possibly other than some primates who walks on two limbs. Each person has his own characteristic gait pattern.

Normal human gait needs good muscle power in the lower limbs, truncal stability, good proprioception, good balance and vision. The movement is rhythmic and smoothened out in to an elegant and sinuous pattern.

Gait Cycle (Fig. 3.2)

The gait cycle is a series of documented movements during walking which by convention is measured from the point of initial heel contact of one lower

Figure 3.2: Phases of gait cycle

extremity to the same point when it occurs again, that is the point at which the heel of the same extremity contacts the ground again. It is divided into 2 phases stance and swing.

When movement is initiated it is called acceleration and when stopping it is called deceleration. Energy is consumed in both phases but more during deceleration. The path taken by the centre of gravity determines the energy expenditure and efficiency of gait. Given the situation, the ideal path should be a sinusoidal curve with minimum displacement. Stance, when the foot is in contact with the ground is the longer component of the gait cycle, using up to 60 per cent of the duration. Swing, which is when the foot is off the ground, forms the rest 40 percent of the cycle. There is a period called double stance covering 11 percent of the cycle when both legs are on the ground.

Studying Normal Human Locomotion

In the analysis of the walking pattern of a person the external effects like the force of gravity, or inertia and internal effects like forces exerted by muscular contraction or angular relationship between the segments, are studied.

Kinematics is the division of mechanics, which deals with the motion of bodies.

It does not study the forces acting to produce the motion. Kinetics is the division of mechanics that deals with forces acting on bodies.

Gait Analysis

Gait analysis commonly involves the measurement of the subjects given above, like the movement of the body in space (kinematics) and the forces involved in producing these movements (kinetics). It is done in a gait lab.

Earlier, the analysis used to be done (and still is done in some places) by photography. Strobe lighting at a predetermined frequency was used in the past to aid in the analysis of gait on single photographic images. Another

method is to use reflective balls as marker systems which are recorded simultaneously through cameras, placed at strategic positions. The patient is made to walk in a straight line on a modified floor embedded with force plates or transducers, which measure force systems, notably the ground reaction force and its magnitude and direction. The system then can calculate the forces and torques about each joint, and the power exerted by muscle groups, throughout the gait cycle. The cameras also measure joint angles and velocities. This information is then analyzed in a software that gives the parameters in 3 dimensions. It is possible for a gait researcher to generate information on the gait pattern and gait variables, description of all gait deviations, energy expenditure and endurance. Based on the analysis of the deviations he will be able to predict the patient’s ambulatory capacity, in the home and community environment.

Observational Gait Analysis

Clinically it is possible to make a study of the gait. The physiatrist makes a study of the patient’s history and condition. Having arrived at a diagnosis, he proceeds to analyze the way the patient walks. If we wish to observe the gait clinically, we need to:

• Measure the distance that the patient has to cover.

• Have an unobstructed view of the patient – in front and by the side.

• The joint or segment to be assessed is selected.

• Observe during the initial part of the stance phase and follow through the entire gait cycle.

• Perform observations on both sides (right and left).

• These observations are recorded for one segment at a time throughout each phase of the gait cycle. For example the physician concentrates on knee extension during the swing phase and records it on a video camera or even on his mobile phone!

• Repeat the process until all joints and segments are completed.

• Check if the gait is normal; if not note the deviations.

Qualitative Gait Analysis

Different reference systems are used in the qualitative gait analysis:

• Absolute spatial system: The environment is used as a reference, and the movement of the body in relation to the environment is studied.

• Relative system: The relative system describes the position of one body segment in relation to another body segment.

• Absolute reference system: The body is given a reference to the x and y and z axis and all segments moving are described in reference to the vertical or horizontal position of the body.

Electrogoniometry: A goniometer is similar to a protractor and measures the angles between the moving segments of the joint at a predetermined point

approximately at the center of the joint. In a clinical set up it is measured manually but using an electrical transducer or a rotational potentiometer, it is possible to get more accurate measurements.

Determinants of Gait

The factors modifying the path taken by the centre of gravity, to smoothen out its extreme movements and reduce the amplitude of displacement, sideways and vertically, are called Determinants of Gait. They are:

Pelvic rotation: While walking, the pelvis rotates by 4 degrees on either side.

This reduces the excursions of the center of gravity and elevates it by 6/16′′.

Pelvic tilt: The pelvis drops on the side of the unsupported or swinging leg during walking and this saves vertical rise of the center of gravity by 3/16"

Knee flexion: During mid stance, the knee bends minimally on the stance leg.

This decreases its length and therefore the height of center of gravity by 7/16". Thus the total saving in the vertical excursion of center of gravity 7/16′′ + 3/16′′ + 6/16′′ = 1 inch.

Knee and ankle movement: There are movements between the knee, ankle, subtalar and mid tarsal joints which act to smoothen out the amplitude of the center of gravity to 2" by flexing, extending, pronating and supinating these joints in a coordinated fashion.

While some determinants act on the amplitude of movements of the center of gravity, there are others which are given below smoothen out the movement of the center of gravity into a sinusoidal curve, and which make the gait energy efficient and sometimes attractive.

Pelvic sway: This is the sideways sway of pelvis, which brings the center of gravity over one leg during stance and produces a side to side sinusoidal curve.

Limb rotation: The leg describes a 25 degree internal rotation on stance and external rotation on swing, smoothening out the sideways curve of the center of gravity.

Some Definitions

Stride length: This is the distance between heel strike of one leg and heel strike of same leg. This is approximately 156 cm on an average.

Step length: This is defined as the distance between heel strike of one foot to heel strike of the other foot (1/2 of stride length).

Stride width: This is the distance between midline of one foot to mid line of the other foot. It works out to 8 cm + 4 cm.

Toe out angle: The angle made by the midline of foot to direction of propulsion.

It varies from 6-7 degrees.

Cadence: This is the number of steps per minute. It ranges from 60 to 120 steps per minute depending on the speed of the gait, the urgency of the person, the build and structure of the person. The mean duration of the gait cycle varies from about 1 to 2 seconds.