Functional Adaptation of the
Human Body and Natural Laws

Virtually all of the human body’s biological systems are remarkably adaptive, and the neuromusculoskeletal system is especially so. In fact, the way we use our bodies every moment of every day determines their neuromusculoskeletal systems’ functional capabilities. Our bodies’ functional capabilities reflect the neuromusculoskeletal systems’ adaptation to our regular activities and the environments in which they are used.

For example, if we challenge our bodies through regular exercise, they adapt and become stronger, more flexible, and more robustly capable. Conversely, if we sit on the couch all day, our bodies will (mal)adapt and become weaker, less flexible, and less capable.

The physiological mechanics of neuromusculoskeletal adaptation is equally reflected in healthy and unhealthy function (mal-adaptation). “Simply put, function is the outcome of any activity.” [1]

[1] R. Gotlin, Sports Injuries Guidebook: Understanding Functional Conditioning

The Natural Laws of Functional Adaptation

The three principal tenets or Natural Laws that describe the physiological mechanics of neuromusculoskeletal adaptation are:

  • Wolff’s Law of Bone Transformation and the Mechnostat Model, which describes how bone models along imposed demands
  • Davis’s Law, which describes how soft tissue models along imposed demands
  • Neuroplasticity, which describes how the nervous system models along imposed demands

Wolff’s Law of Bone Transformation and The Mechanostat Theorem

Wolff’s Law and the Mechanostat Theorem describe bone plasticity and the relationship between muscle and bone, specifically the way in which bone adapts to the mechanical loads/stresses under which it is placed and the effect on bone density, flexibility, and shape.

Healthy loads/stresses increase and maintain bone density, flexibility, and shape. Healthy loads/stresses are those that are varied in both intensity and direction. Aside from injuries caused by trauma (car crash or fall), unhealthy loads/stresses on bone affect the bone in different ways:

When loads/stresses are chronically unvaried and insufficient.

They cause loss of bone density and flexibility, as well as deformation. This type of adaptation is seen in astronauts who spend time in space, when a body part is immobilized (casted, splinted, or braced), in those who get little physical activity or are inactive, and in those who habitually wear conventional footwear.

When loads/stresses are chronic and greater than the mechanical tolerance of the bone.

They cause stress fractures (fatigue fractures) as well as deformation. This type of adaptation is commonly seen in athletes exhibiting poor neuromuscular function/bone alignment from habitually wearing conventional footwear, and participating in repetitious high intensity activities on hard surfaces for a long period of time. One common example is shin splint-related stress fractures.

When loads/stresses are chronically unvaried and compressive.

They can cause loss of bone density and flexibility, as well as deformation (the bone models away from the constant pressure. This type of adaptation is seen when braces are used to straighten teeth (where the constant tension created by the braces’ rubber band puts pressure on the teeth that is transferred to the bone (tooth sockets) causing the bone to model away from the constant pressure. It is also seen when tight restrictive footwear causes bone to model away from constant pressure (as seen when the shape of the toes deform due to pointy toed footwear). One common example is hallux valgus. An extreme example is the practice of Chinese foot binding.

When loads/stresses are chronically intermittent and localized.

They can cause bone deformation (the bone models towards from the intermittent localized pressure. This type of adaptation is seen in the formation of heel spurs, bunions, and bunionettes, which are caused by poor neuromuscular foot function (instability) in those who habitually wear conventional footwear.

Davis’s Law of Soft Tissue Adaptation

Davis’s Law is a corollary of Wolff’s Law pertaining to soft tissues and is commonly cited in the fields of anatomy and physiology. It describes how soft tissue and, principally, tissue containing collagen fibers (i.e., ligaments, tendons, and fascia) will model via imposed demands similar to how Wolff’s Law describes the same for bone. It is used in part to describe muscle length relationships and thus helps to predict the effects of rehabilitation and postural distortion treatments in which muscle length is of concern.

Healthy demands (loads/stresses) increase and maintain soft tissue (muscle, ligament, tendon, and fascia) functional robustness, strength, and flexibility. Healthy loads/stresses are those that are varied in both intensity and are multi-directional.

Aside from injuries caused by trauma (car crash or fall), unhealthy demands (loads/stresses) on soft tissue affect the soft tissue in different ways:

When demands are chronically insufficient or unvaried.

They cause loss of functional robustness, strength, and flexibility, as well as atrophy. This type of adaptation is seen in astronauts who spend time in space, when a body part is immobilized (casted, splinted, or braced), in those who get little physical activity or are inactive, and in those who habitually wear conventional footwear.

When demands are acute and greater than the soft tissue’s mechanical tolerance.

They cause soft tissue tears, sprains, and ruptures, which ultimately lead to the formation of fibrotic tissue. This type of adaptation is commonly seen in athletes exhibiting poor neuromuscular function/bone alignment, particularly those who participate in high intensity activities while wearing conventional footwear. Common examples are torn knee and ankle ligaments, Achilles tendon ruptures, and turf toe.

When demands are chronic and greater than the mechanical tolerance of the soft tissue.

They cause stress micro-tears and the formation of fibrotic tissue. This type of adaptation is commonly seen in athletes exhibiting poor neuromuscular function/bone alignment, particularly those who participate in repetitious activities while wearing conventional footwear. Common examples are plantar fasciitis, IT Band Syndrome, and shin splints.

When demands are chronically unbalanced (between opposing muscle groups).

They can cause loss of joint flexibility. This type of adaptation is seen when a muscle group is overused due to poor technique activities, and in those who habitually wear conventional footwear. Common examples are seen in the knee, lower back, and in hammertoes, over pronation, and over supination.

Neuroplasticity

Neuroplasticity describes the ability of the brain and nervous system to form and reorganize synaptic connections, especially in response to learning, or experience, or following injury. In essence, as with bone and soft tissue, the nervous system and its related functional capabilities are continuously adapting to the everyday demands that we place on our bodies, how we use them, and the environment we use them in.

Neuroplasticity Chart

Healthy demands that enhance our nervous system’s functional robustness are those that are new (when learning to do new things) and those that varied in both intensity and activity without being overwhelming. Unhealthy demands that impair our nervous system’s functional robustness are those that are unvaried in intensity and activity, those that exhibit a lack of activity, and those that overwhelm the nervous system.

Neuroplasticity and Sensory Motor Systems

Innate body intelligence—protective reflexes

From a body movement perspective, reflexes are automatic involuntary neuromuscular actions or movements activated by the nervous system. These innate nervous system actions do not require conscious thought to take effect.

Types of Neuromuscular Reflexes

A stretch reflex is a muscle contraction in response to stretching within the muscle. It is not controlled by the brain and is a monosynaptic response that is transmitted to the spinal cord. Its major function is to protect the muscle and is important in maintaining the body’s posture and balance when walking or running.

A nociceptive reflex is a withdrawal reflex initiated by pain or an irritant that protects the body from the damaging stimuli. Pulling one’s hand away from a hot stove is an example.

A conditioned reflex is one acquired as the result of experience. When an action is performed repeatedly, the nervous system becomes familiar with the situation and learns to react automatically, building a new reflex into the system. Walking, running, writing with a pen, and driving a car are examples of activities that require large number of complex muscle coordination that have become automatic.

A proprioceptive reflex is induced by stimulation of proprioceptors. It affects the spatial positioning of the limbs and their parts in relation to each other and the body’s core. Proprioceptive reflexes are involved in stretch, nociceptive, and conditioned reflex activities.

A superficial reflex is any withdrawal reflex elicited by noxious or stimulation of the skin, cornea, or mucous membrane. Examples of superficial reflexes are blinking and coughing.

Protective Extension reflexes are developed during a child’s development process and involve protecting the body from a loss of balance, such as when you straighten your arms to catch yourself when you fall.

A protective reflex, also called a protective response, is the reflexive withdrawal of the body or part(s) of the body from either actual or perceived painful stimuli. A protective response may involve some or all of the reflex actions noted above.

All of the above reflex actions can be enhanced or diminished by functional conditioning. For example, improved or enhanced reflexes are seen in the movement speed and positioning of a martial artists’ or athletes’ body part as a result of their training, and in those who habitually do not wear shoes.

Diminished reflex activity is seen in those who have had a body part immobilized by a splint, cast, or footwear and whose affected body part(s) are only capable of limited slow movement as a result.

Diminished reflex activity is also seen in those who have sedentary lifestyles, or when natural external stimulus is dampened by artificial cushioning that causes the cushioned body part to lose its neuromuscular functional robustness.

Imgnotracat Arc Reflex Illustration
Illustration by Marta Aguayo, used under License CC BY-SA 3.0

Debunking Some of the Myths

MYTHS

MYTH

Cushioning reduces damaging shock and stress.

NATURAL LAWS

NATURAL LAW

In reality, cushioning results in:

  • dampened sensory input
  • reduced functional robustness of the neuromuscular system
  • poor inefficient skeletal alignment
  • increased damaging stresses

MYTH

Orthotics correct faulty foot biomechanics.

NATURAL LAW

In reality, use of supportive orthotics results in:

  • dampened varied sensory input
  • neuromuscular system atrophy and loss of functional robustness
  • skeletal atrophy
  • increased damaging stresses

MYTH

It is important to wear good supportive shoes.

NATURAL LAW

In reality, use of supportive footwear results in:

  • dampened varied sensory input
  • neuromuscular system atrophy and loss of functional robustness
  • skeletal atrophy
  • inefficient skeletal alignment

Learn More About the Science Behind BioPods

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