Definitions:
Neuromuscular function – is the muscle activity that is initiated by the brain via the central nervous system.
Neuromusculoskeletal function - is the skeletal alignment created by neuromuscular function.
Reflex function - is reflexive neuromuscular function (i.e., not consciously initiated).
Maladaptive and maladapted - is unhealthy adaptation.
Proprioception - is the sense of spatial orientation of the body and its parts in relation to each other.
Right Stimulus - refers to stimuli that activates healthy neuromuscular function.
Right Movement - refers to healthy neuromuscular movement.
Functional and Anatomical Maladaptations
Maladaptive, neuromusculoskeletal function, and related maladapted reflex function, are typically observed in shoe-wearing populations.
This poor function occurs because the cushioning, restrictive, and supportive characteristics of footwear can create the following consequences:
- Proprioceptive, sensory input, and tactile stimuli (‘Right Stimulus’) are dampened, resulting in insufficient stimuli for efficient muscle function.
- Natural, healthy, dynamic movement (‘Right Movement’) throughout the feet, ankles, legs, hips, and lower back is restricted or encumbered.
- Impairment of force management capabilities in feet and lower limbs throughout the demands of three-dimensional activities.
During maladaptive neuromusculoskeletal function, impairment occurs in: 1 - the movement being generated; 2 - the sensory input (especially the proprioceptive input); and 3 - the tactile stimulus created during each foot's ground contact. These impairments are caused by the following:
- Artificial cushioning dampens the tactile sensory input (‘Right Stimulus’) required to initiate an adequate protective reflex response during reflex-activated anticipation (or preparation) for the next step (while the foot is off the ground),
- Artificial support and restrictions to musculoskeletal ‘Right Movement’ impede the dynamic three-dimensional movement of the musculoskeletal structure, leading to instability.
Consequently, the following can happen:
- Muscles do not receive the signals required for effective alignment and stability of the bones in the foot, ankle, and leg (before ground contact).
- The bones of the foot, ankle, and leg cannot dynamically align and stabilize because of the "support" or "restrictions" throughout all skeletal and neuromuscular gait phases.
As a result, the neuromusculoskeletal structure becomes incapable of safely managing the forces created during walking or running and its performance capabilities are impeded by compensatory, imbalanced and inefficient muscle use.
The stressors that are generated cause damage and contribute to the creation of a less robust neuromusculoskeletal structure (i.e., weaker and less flexible), significantly increasing the risk of injury.
In short, the shoe-wearing environment promotes ‘Poor Technique’.
Over time and after many repetitions, maladaptive neuromusculoskeletal mechanics become the ‘Maladapted Reflex Condition’. However, due to the body's remarkable adaptive properties, the ‘Maladapted Reflex Condition’ is easily reconditioned or retrained to become the ‘Habitual Optimal Functional Condition’ by employing ‘Proper Technique’ activities of sufficient intensity and duration.
For example, a ‘Maladapted Reflex Condition’ develops when a limb is placed in a splint or cast. Even after a relatively short period of two weeks, atrophy, joint stiffness, loss of soft tissue resiliency, and diminished protective reflex capabilities will be noticeable. In these cases, rehabilitative therapies (exercise programs) are commonly employed to regain optimal function.
Footwear design characteristics and gait-related pathology
It is commonly accepted that poor foot biomechanics play a significant role in the development of pathologies that include metatarsalgia, plantar fasciitis, hallux valgus, heel spurs, neuromas, Achilles tendonitis, shin splints, patello-femoral syndromes, hip and back pain. Although it is often argued that genetics plays a key role in dysfunctional foot biomechanics, there is very little science to support this hypothesis. Conversely, there is abundant scientific evidence that points to footwear as the leading cause of foot dysfunction and most associated foot-related pathologies.
Most conventional footwear designs affect the feet, much like a cast or splint affects an arm or leg. Chronic restrictions imposed by footwear cause muscle atrophy, loss of bone mass, less-than-ideal bone geometry (through remodeling), and joint stiffness. Wearing shoes can weaken the feet and legs, increasing their susceptibility to injury.
Shoes insulate the soles of the feet from the subtle, varied ‘Right Stimulus’ required for optimal neuromuscular function throughout the lower limb-hip-back kinetic chain. The dampened stimulus impairs the timing and intensity of optimal ‘Right Movement’ muscle activity throughout the kinetic chain. This impairment effectively destabilizes the limb’s dynamic load bearing and propulsion capabilities (i.e., dynamic alignment and muscle efficiencies are impaired). This dynamic instability leads to degenerative stresses in the muscles and at joints that cause or contribute to various "arthritic-like" problems (and eventually, pathologies) in the feet, legs, hips, and back.
In addition to improper sizing, there are many ways that footwear design characteristics contribute to poor foot function. (See: Choosing the Right Footwear)
Footwear can impair nociceptive and proprioceptive sensory feedback
A shoe that features abundant cushioning significantly diminishes the subtle, varied, sensory input required for optimal "natural", ‘Right Stimulus’, reflex, muscle-firing sequences that stabilize the arch.
A shoe that is rigid or supportive inhibits the "natural", ‘Right Movement’ that is necessary to stabilize the foot and ankle. According to Robbins, “Wearers of expensive running shoes that are promoted as having additional features that protect (more cushioning, pronation correction), are injured significantly more frequently than runners employing inexpensive shoes (costing less than US $40)." *1
Modern footwear – running shoes, in particular – substantially diminish sensory feedback but does not diminish injury-inducing impact. That is a dangerous situation.
Supportive cushioning features are widely promoted as essential for safety when walking or running to mitigate chronic overload on the lower extremities due to the foot’s purported inherent fragility. This purported fragility is inconsistent with reports that indicate habitually unshod humans are not subject to chronic overloading when running and are virtually free of foot-related pathologies.
Considerable research indicates that the lower extremities of predominantly barefoot populations are inherently durable and that chronic overloading is a consequence of wearing footwear. Studies on barefoot people suggest that, because of the intrinsic properties of biomechanically sound feet unfettered by the constrictions of footwear, they can effectively manage the forces and stresses generated during most rigorous activities on the hardest surfaces. Man-made cushioning and motion control designs pale in comparison.
*1 Robbins SE, Gerard GJ. Athletic Footwear: Unsafe Due to Perceptual Illusions. Medicine and Science in Sports and Exercise 23(2): p. 217, 1991.
