Understanding Human Movement: Muscles, Bipedalism, and Gait

The Basis of Movement

The foundation of movement, mediated by muscle cells, is the conversion of chemical energy into mechanical energy by the contractile apparatus of muscle cells. Actin and myosin proteins are essential components of this contractile apparatus. The interaction of these proteins facilitates the contraction of muscle cells.

Characteristics of Muscle Tissue

  • Irritability: Muscles receive and respond to stimulation.
  • Contractility: Muscles can change shape, becoming shorter and thicker.
  • Extendibility: Living muscle cells can be stretched and extended, becoming longer and thinner.
  • Elasticity: After the removal of a distending force, a muscle cell returns to its original form.

Types of Muscle Tissue

  • Smooth Muscle: Smooth muscle fiber is short and contains a single, centrally located nucleus. Smooth muscle is part of the visceral or involuntary muscle system.
  • Cardiac Muscle: Cardiac muscle consists of single muscle cells with centrally located nuclei. Its innervation is provided by the autonomic nervous system.
  • Skeletal Muscle: Skeletal muscle consists of several very long, tubular cells, also called muscle fibers. Skeletal muscle fibers contain many nuclei located peripherally. In many preparations, skeletal muscle fibers exhibit characteristic striations, hence the name striated muscle.

Muscle Function

  • Tonic or Postural Muscles: These muscles have a static function and are important in maintaining balance. They act based on proprioceptive information and tend to shorten.
  • Phasic Muscles: These muscles play an active role and are involved in movement. They undergo voluntary contraction and may atrophy if not used.

Bipedal Walk

Advantages of Bipedalism

  • Increased sight range
  • Hands are freed from locomotor function, allowing for manipulation and carrying objects.
  • Locomotion becomes more energy-efficient over long distances.

Disadvantages of Bipedalism

  • Reduced speed and speed limits.
  • More difficult childbirth due to increased cranial capacity.

Bipedalism was facilitated by a combination of adjustments: A shorter and wider pelvis, a curved spine, a toe that becomes parallel to the rest, a longer lower limb length, and a shorter length of the upper extremities.

Why bipedalism evolved: For energy efficiency, predator avoidance, navigating high grass, and wading in deep water.

Walking Gait

Setting up: Walking is a complex act that allows for the movement of an individual as a result of mental development, involving various organs, apparatuses, and systems.

Walking Phases

  • Dual back support of the march
  • Swing
  • Double support reception earlier
  • Unilateral support

Abnormal Gaits

Hemiparetic March

This type of gait is caused by a lesion of the pyramidal tract.

Tiptoe Gait

The patient walks on the tips of the fingers or toes.

Ataxia

Ataxia is defined as impaired coordination of voluntary movements and balance.

Steppage Gait

Characterized by difficulty with dorsiflexion of the foot. To avoid dragging the foot during walking, the patient exhibits exaggerated knee lift and supports the foot with the tip.

Myopathic March

In this type of gait, the patient exhibits involvement of the pelvic girdle muscles, resulting in a swaying walk.

Choreic March

Accompanied by sudden movements of large amplitude.

Marches of Psychosomatic Origin

These do not show a particular feature. From a distance, it simulates ataxia, balance disorder, or dystonia.

Foot Deformities

Flat Feet

Characterized by the decrease or disappearance of the plantar arch.

Cavus Foot

Occurs when the arc from the toes to the heel is too high.

Varus Foot

The heel looks inward and is directed inward.

Pes Valgus

The heel looks outward and goes out.

Clubfoot

Any foot that does not rest on the floor on its normal support.

Equinus Foot

The foot is in plantar flexion of the ankle.