Locomotor effects of shoes
Encyclopedia
Locomotor effects of shoes describes how physical characteristics or components of shoes influence the locomotion neuromechanics of a person. Depending on the characteristics of the shoes, the effects are various, ranging from alteration in balance and posture, muscle activity of different muscles as measured by electromyography (EMG
), and the impact force. There are many different types of shoes that exist, such as running, walking, loafers, high heels, sandals, slippers, work boots, dress shoes, and many more. However, a typical shoe will be composed of an insole, midsole, outsole, and heels, if any. In an unshod condition, where one is without any shoes, the locomotor effects are primarily observed in the heel strike patterns and resulting impact forces generated on the ground.
through cutaneous afferent
feedback, which originates from the special mechanoreceptors within the plantar surface of the foot. This afferent feedback has a strong influence on postural stability and balance correction during standing and walking. Since sensory feedback from the foot may be influenced by the interaction of the foot with the insole surface, different types of insoles and shoe inserts have been used to try and enhance postural stability.
and in EMG amplitude of ankle flexor and extensor muscles. Textured inserts mostly affect ankle motion in the sagittal plane, where plantar flexion of the foot is increased. As for muscle activity, textured inserts decrease the activation of soleus and tibialis anterior muscles during standing and walking.
(COM) of the body must be positioned over the base of support (BOS) established by the feet. Cutaneous feedback from the feet is necessary to provide the central nervous system
(CNS) with the information about the proximity of the COM to the BOS limit, which is an important parameter for the maintenance of balance and stable gait.
Since plantar pressure sensation aids in balancing reactions in stepping movements, insoles with raised ridges along the edges can enhance stimulation of cutaneous mechanoreceptors that help to define the BOS. Most of the time, the ridges are made so that stimulation only occurs when the COM nears the BOS limit. Insoles with ridges appear to reduce the likelihood that the COM motion will exceed the BOS limit in the lateral direction, thereby resulting in a stabilizing effect on gait. Furthermore, the magnitude of this effect did not diminish with time, which suggests the CNS did not habituate to heightened cutaneous stimulation. Therefore, insoles with ridges can aid in reducing the fall rates among elderly populations.
midsoles are denser and more supportive while ethylene vinyl acetate is used to make lighter and more compliant midsoles.
amplitude for tibialis anterior have shown to be significantly greater before the heel strike and lower following the heel strike than compared to the neutral midsole. Furthermore, walking in shoes with stiffer midsole appears to significantly reduce the energy dissipated at the metatarsophalangeal joints and aid in improving jumping performances and running economy
. However, the underlying mechanisms that can be attributed to this improvement are still not fully understood.
of the foot, much research has been conducted with different types of midsoles that could possibly aid in prevention of such injuries. The varus
-wedged shoes, which have a medial incline, seem to decrease pronation
during stance time, reduce the net inversion of the joint moment, and decrease the activities of the inverter muscles, such as tibialis posterior, gastrocnemius, and soleus. The valgus-wedged shoes, which have an lateral incline, are designed to accentuate pronation and have the opposite effect as the varus-wedged shoes. Also when walking in valgus-wedged shoes, it may lead to an increase in calcaneus eversion
and up to 58% of energy absorption in the frontal plane of the body.
During gait, high heeled shoes are shown to affect the ankle joint, causing significantly increased plantarflexion
. This, in turn, increases the metabolic costs of walking and leads to faster muscle fatigue. Accelerated muscle fatigue may then increase the likelihood of ankle sprains and or falls due to impaired foot and ankle stability. Wearing high heels can also lead to shorter stride lengths, greater stance time, unstable posture and gait, and a decrease in lumbar flexion angles.
Changes to muscle activity are also observed with high heeled shoes, mostly affecting the tibialis anterior and erector spinae
muscles. The increase in plantar flexion of the foot causes the EMG amplitude of tibialis anterior to increase. The high heels also lead to a decrease in the lumbar flexion angle due to a compensatory mechanism to prevent one from falling forward. This arching of the back causes the erector spinae to increase its activity.
In addition, increased heel height may lead to numerous foot problems including:
In contrast, moderate heel elevation has also been used as a conservative treatment for plantar fasciitis
to decrease strain in the plantar fascia
. Although various locomotor effects of heels are prominent, the practical health implications are still debatable.
Walking in negative heeled shoes leads to a faster cadence
and shorter stride length, resulting in a significantly shorter stride cycle time than when walking with a natural cadence. The range of the ankle motion is also significantly greater in the negative heeled shoes, remaining in dorsiflexion longer throughout the stance and swing phases of gait. The increased duration of dorsiflexion leads to lengthening of the gastrocnemius and soleus muscle-tendon units and the length of the moment arm of the Achilles tendon. A similar post-operative exercise effect involving increased dorsiflexion is often desired after surgeries involving the gastrocnemius and soleus muscles or Achilles tendon. The purpose of the exercise is to increase the range of motion in the ankle joint and strengthen the gastrocnemius and soleus muscles and the Achilles tendons. Wearing negative heeled shoes, therefore, may offer an alternative method for post-operative rehabilitation in these situations. It should be noted that while dorsiflexion of the ankle may be beneficial, it also causes the center of gravity to shift backward, which can cause instability and difficulty in propelling forward during gait.
When walking in negative heeled shoes, muscle activity of gastrocnemius and tibialis anterior muscles are similar to that observed in uphill walking. The duration of the EMG activity is longer and the EMG amplitude is higher for the calf and the biceps femoris muscles than compared to normal shoes. Also the EMG readings for the rectus femoris and biceps femoris indicate an enhanced co-contraction of the two muscles, and therefore the negative heeled shoes may be helpful in exercising these muscle groups.
. Much of the research on unshod locomotion has been conducted on barefoot running
. However, some of the learned principles may apply to both running and walking.
run very differently than the typical shod runners. Shod runners tend to heel strike due to the designs of the modern shoes, which have thick heels to reduce the impact force from the ground. When running barefoot, however, some runners tend to shift to a forefoot striking pattern to avoid such impact, which is equivalent to 2-3 times the body weight. The forefoot strike is where the forefoot lands first, followed by the heels coming down. The midfoot strike is characterized by the heel and the ball of the foot landing at the same time, and heel strike is where the heel lands first followed by the forefoot.
Those who wish to approximate the experience of running barefoot, but would prefer some protection, can resort to shoes that mimic barefoot locomotion. Such shoes as water socks, running sandals, moccasins, huaraches
, dime-store plimsolls, Vibram FiveFingers
footwear and other minimal running shoes have relatively thin soles but provide some protection. However minimal shoes do not give runners the same feedback from the plantar mechanoreceptor
s. Because of the greater protection they offer in comparison to barefoot running, minimal shoes may also interfere with the development of a gentle foot strike, toughening of the soles of the feet, and awareness of road hazards.
Electromyography
Electromyography is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph, to produce a record called an electromyogram. An electromyograph detects the electrical potential generated by muscle...
), and the impact force. There are many different types of shoes that exist, such as running, walking, loafers, high heels, sandals, slippers, work boots, dress shoes, and many more. However, a typical shoe will be composed of an insole, midsole, outsole, and heels, if any. In an unshod condition, where one is without any shoes, the locomotor effects are primarily observed in the heel strike patterns and resulting impact forces generated on the ground.
Insoles and inserts
The foot provides the sensory information to the central nervous systemCentral nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
through cutaneous afferent
Afferent
Afferent is an anatomical term with the following meanings:*Conveying towards a center, for example the afferent arterioles conveying blood towards the Bowman's capsule in the Kidney. Opposite to Efferent.*Something that so conducts, see Afferent nerve fiber...
feedback, which originates from the special mechanoreceptors within the plantar surface of the foot. This afferent feedback has a strong influence on postural stability and balance correction during standing and walking. Since sensory feedback from the foot may be influenced by the interaction of the foot with the insole surface, different types of insoles and shoe inserts have been used to try and enhance postural stability.
Textured inserts
Textured Inserts are regular shoe inserts that have a raised textured surface on the side that acts to provide enhanced mechanical contact and pressure on the plantar surface of the feet. Providing a textured surface of the shoe insert leads to significant changes during gait in ankle joint kinematicsKinematics
Kinematics is the branch of classical mechanics that describes the motion of bodies and systems without consideration of the forces that cause the motion....
and in EMG amplitude of ankle flexor and extensor muscles. Textured inserts mostly affect ankle motion in the sagittal plane, where plantar flexion of the foot is increased. As for muscle activity, textured inserts decrease the activation of soleus and tibialis anterior muscles during standing and walking.
Insoles with ridges
One of the most pervasive effects of aging is the loss of cutaneous and pressure sensation, which has been correlated with impaired balance control and increased risk of falling. This is because for an upright stance, the center of massCenter of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...
(COM) of the body must be positioned over the base of support (BOS) established by the feet. Cutaneous feedback from the feet is necessary to provide the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
(CNS) with the information about the proximity of the COM to the BOS limit, which is an important parameter for the maintenance of balance and stable gait.
Since plantar pressure sensation aids in balancing reactions in stepping movements, insoles with raised ridges along the edges can enhance stimulation of cutaneous mechanoreceptors that help to define the BOS. Most of the time, the ridges are made so that stimulation only occurs when the COM nears the BOS limit. Insoles with ridges appear to reduce the likelihood that the COM motion will exceed the BOS limit in the lateral direction, thereby resulting in a stabilizing effect on gait. Furthermore, the magnitude of this effect did not diminish with time, which suggests the CNS did not habituate to heightened cutaneous stimulation. Therefore, insoles with ridges can aid in reducing the fall rates among elderly populations.
Midsole
The midsole is between the outer sole(bottommost) and the insole(topmost) parts of the shoe sole. It can be made of a variety of materials to give the shoe different mechanical characteristics of cushioning, support, and flexibility. PolyurethanePolyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
midsoles are denser and more supportive while ethylene vinyl acetate is used to make lighter and more compliant midsoles.
Density/stiffness
By changing the material hardness of the midsole, one will be able to change the EMG activity in various lower extremity muscles such as rectus femoris, biceps femoris, medial gastrocnemius, and tibialis anterior. Especially when running with the stiffer midsole, the EMGEMG
EMG can refer to:*Electromyography, a technique for evaluating physiologic properties of muscles*EMG, Inc., a company that manufactures guitar pickups.*Escape Media Group, Inc., the company that created Grooveshark...
amplitude for tibialis anterior have shown to be significantly greater before the heel strike and lower following the heel strike than compared to the neutral midsole. Furthermore, walking in shoes with stiffer midsole appears to significantly reduce the energy dissipated at the metatarsophalangeal joints and aid in improving jumping performances and running economy
Running economy
Running economy is a measure of how efficiently a person uses oxygen while running at a given pace. Expressed as the rate of oxygen consumption per distance covered , running economy is the energy required running submaximally at a given velocity. Those who are able to consume less oxygen while...
. However, the underlying mechanisms that can be attributed to this improvement are still not fully understood.
Midsole wedging
With the increasing number of injuries associated with excessive pronationPronation
In anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...
of the foot, much research has been conducted with different types of midsoles that could possibly aid in prevention of such injuries. The varus
Varus deformity
In orthopedics, a varus deformity is a term for the inward angulation of the distal segment of a bone or joint. The opposite of varus is called valgus.The terms varus and valgus always refer to the direction that the distal segment of the joint points....
-wedged shoes, which have a medial incline, seem to decrease pronation
Pronation
In anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...
during stance time, reduce the net inversion of the joint moment, and decrease the activities of the inverter muscles, such as tibialis posterior, gastrocnemius, and soleus. The valgus-wedged shoes, which have an lateral incline, are designed to accentuate pronation and have the opposite effect as the varus-wedged shoes. Also when walking in valgus-wedged shoes, it may lead to an increase in calcaneus eversion
Eversion
Eversion is a process of turning inside-out. To Evert means to turn inside out. Eversion may refer to:* Eversion , the anatomical term of motion denoting the movement of the sole of the foot away from the median plane...
and up to 58% of energy absorption in the frontal plane of the body.
Heel height
Shoe heel height can have significant biomechanical effects on the shoe wearer that can be detrimental or beneficial.High heels
High heels are shoes where the rearfoot(the heel) is positioned higher than the forefoot(toes). High heels of various heights are worn by men and women on a daily basis. The main reason many people wear high heeled shoes is for aesthetic purposes, where high heels are believed to enhance the wearer's physical appearance. These same high heeled shoes, however, can have undesirable biomechanical effects.During gait, high heeled shoes are shown to affect the ankle joint, causing significantly increased plantarflexion
Plantarflexion
Plantarflexion is the movement which increases the approximate 90 degree angle between the front part of the foot and the shin, as when depressing an automobile pedal...
. This, in turn, increases the metabolic costs of walking and leads to faster muscle fatigue. Accelerated muscle fatigue may then increase the likelihood of ankle sprains and or falls due to impaired foot and ankle stability. Wearing high heels can also lead to shorter stride lengths, greater stance time, unstable posture and gait, and a decrease in lumbar flexion angles.
Changes to muscle activity are also observed with high heeled shoes, mostly affecting the tibialis anterior and erector spinae
Erector spinae
The Erector spinæ is a muscle group of the back in humans and animals. It is also known as sacrospinalis in older texts. A more modern term is extensor spinae, though this is not in widespread use. The name of the muscle is pronounced e-rec-tor speen-aye, or e-rec-tor spinae-ee.It is really not...
muscles. The increase in plantar flexion of the foot causes the EMG amplitude of tibialis anterior to increase. The high heels also lead to a decrease in the lumbar flexion angle due to a compensatory mechanism to prevent one from falling forward. This arching of the back causes the erector spinae to increase its activity.
In addition, increased heel height may lead to numerous foot problems including:
- callusCallusA callus is an especially toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritation. Rubbing that is too frequent or forceful will cause blisters rather than allow calluses to form. Since repeated contact is required, calluses...
es - foot pain
- blisterBlisterA blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing , burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum or plasma...
s - hammer toeHammer toeA hammer toe or contracted toe is a deformity of the proximal interphalangeal joint of the second, third, or fourth toe causing it to be permanently bent, resembling a hammer...
s - bunionBunionA bunion is a deformity characterized by lateral deviation of the great toe, often erroneously described as an enlargement of bone or tissue around the joint at the head of the big toe...
s (hallux valgus) - Morton’s neuromaMorton's neuromaMorton's neuroma is a benign neuroma of an intermetatarsal plantar nerve, most commonly of the third and fourth intermetatarsal spaces.This problem is characterised by pain and/or numbness, sometimes relieved by removing footwear.Despite the name, the...
- metatarsalgiaMetatarsalgiaMetatarsalgia is a general term used to refer to any painful foot condition affecting the metatarsal region of the foot. This is a common problem that can affect the joints and bones of the metatarsals. Metatarsalgia is most often localized to the first metatarsal head...
- ankle sprain
- shortened Achilles tendons
- high heel cords
- osteoarthritisOsteoarthritisOsteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...
in the knee.
In contrast, moderate heel elevation has also been used as a conservative treatment for plantar fasciitis
Plantar fasciitis
Plantar fasciitis is a painful inflammatory process of the plantar fascia, the connective tissue on the sole of the foot.Longstanding cases of plantar fasciitis often demonstrate more degenerative changes than inflammatory changes, in which case they are termed plantar fasciosis. The suffix...
to decrease strain in the plantar fascia
Plantar fascia
The plantar fascia is the thick connective tissue which supports the arch on the bottom of the foot. It runs from the tuberosity of the calcaneus forward to the heads of the metatarsal bones .The often painful condition plantar fasciitis is an inflammatory condition of the plantar...
. Although various locomotor effects of heels are prominent, the practical health implications are still debatable.
Negative heels
Negative heeled shoes, which are also known as earth shoes, are shoes that are designed to mimic uphill walking to increase the resistance training effect on the leg muscles during normal walking. The forefoot(toes) of the shoe is 1.5 cm higher than the heel of the shoes, creating an approximately 10 degree angle of dorsiflexion at the ankle during stance on level ground.Walking in negative heeled shoes leads to a faster cadence
Cadence (gait)
Cadence in sports involving running is the total number of 'revolutions per minute' , or number of full cycles taken within a minute, by the pair of feet, and is used as a measure of athletic performance. It is very similar in respect to cadence in cycling, however it is often overlooked in its...
and shorter stride length, resulting in a significantly shorter stride cycle time than when walking with a natural cadence. The range of the ankle motion is also significantly greater in the negative heeled shoes, remaining in dorsiflexion longer throughout the stance and swing phases of gait. The increased duration of dorsiflexion leads to lengthening of the gastrocnemius and soleus muscle-tendon units and the length of the moment arm of the Achilles tendon. A similar post-operative exercise effect involving increased dorsiflexion is often desired after surgeries involving the gastrocnemius and soleus muscles or Achilles tendon. The purpose of the exercise is to increase the range of motion in the ankle joint and strengthen the gastrocnemius and soleus muscles and the Achilles tendons. Wearing negative heeled shoes, therefore, may offer an alternative method for post-operative rehabilitation in these situations. It should be noted that while dorsiflexion of the ankle may be beneficial, it also causes the center of gravity to shift backward, which can cause instability and difficulty in propelling forward during gait.
When walking in negative heeled shoes, muscle activity of gastrocnemius and tibialis anterior muscles are similar to that observed in uphill walking. The duration of the EMG activity is longer and the EMG amplitude is higher for the calf and the biceps femoris muscles than compared to normal shoes. Also the EMG readings for the rectus femoris and biceps femoris indicate an enhanced co-contraction of the two muscles, and therefore the negative heeled shoes may be helpful in exercising these muscle groups.
Barefoot (Unshod)
Unshod condition is where one is without any shoes, or is barefootBarefoot
Barefoot is the state of not wearing any footwear. Being barefoot is regarded as a human's natural state, though for functional, fashion and social reasons footwear is worn, at least on some occasions...
. Much of the research on unshod locomotion has been conducted on barefoot running
Barefoot running
Barefoot running is running while barefoot—without wearing any shoes on the feet. Running in thin-soled, flexible shoes, often called minimalist running, such as moccasins is biomechanically related to running barefoot, but alters sensory feedback from the plantar mechanoreceptors...
. However, some of the learned principles may apply to both running and walking.
Foot strike patterns
Barefoot runnersBarefoot running
Barefoot running is running while barefoot—without wearing any shoes on the feet. Running in thin-soled, flexible shoes, often called minimalist running, such as moccasins is biomechanically related to running barefoot, but alters sensory feedback from the plantar mechanoreceptors...
run very differently than the typical shod runners. Shod runners tend to heel strike due to the designs of the modern shoes, which have thick heels to reduce the impact force from the ground. When running barefoot, however, some runners tend to shift to a forefoot striking pattern to avoid such impact, which is equivalent to 2-3 times the body weight. The forefoot strike is where the forefoot lands first, followed by the heels coming down. The midfoot strike is characterized by the heel and the ball of the foot landing at the same time, and heel strike is where the heel lands first followed by the forefoot.
Impact forces
In barefoot locomotion, the impact force (impact transient) on the ground is diminished compared to shod running. It has been suggested that unshod runners are better able to take advantage of elastic energy storage in the Achilles tendon and arch of the foot, and can avoid potential injury due to repetitive impact of the heel bone (calcaneus) due to heel striking. However, the long-term and actual health benefits of unshod running are still not well understood and remain an area of active research.Those who wish to approximate the experience of running barefoot, but would prefer some protection, can resort to shoes that mimic barefoot locomotion. Such shoes as water socks, running sandals, moccasins, huaraches
Huarache (shoe)
Huaraches are a type of Mexican sandal.Huaraches are pre-Columbian in origin, and are made from woven leather. The leather is traditionally hand-woven. The name "Huarache" is derived from the P'urhépecha language term kwarachi...
, dime-store plimsolls, Vibram FiveFingers
FiveFingers
Vibram FiveFingers are a type of minimalist shoe manufactured by Vibram, originally marketed as a more "natural" alternative for different outdoors activities . The footwear has thin, flexible soles that are contoured to the shape of the human foot, including visible individual sections for the toes...
footwear and other minimal running shoes have relatively thin soles but provide some protection. However minimal shoes do not give runners the same feedback from the plantar mechanoreceptor
Mechanoreceptor
A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. There are four main types in the glabrous skin of humans: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles...
s. Because of the greater protection they offer in comparison to barefoot running, minimal shoes may also interfere with the development of a gentle foot strike, toughening of the soles of the feet, and awareness of road hazards.
See also
- ShoeShoeA shoe is an item of footwear intended to protect and comfort the human foot while doing various activities. Shoes are also used as an item of decoration. The design of shoes has varied enormously through time and from culture to culture, with appearance originally being tied to function...
- High-heeled footwear
- Barefoot runningBarefoot runningBarefoot running is running while barefoot—without wearing any shoes on the feet. Running in thin-soled, flexible shoes, often called minimalist running, such as moccasins is biomechanically related to running barefoot, but alters sensory feedback from the plantar mechanoreceptors...
- Barefoot movement
- Comparative foot morphologyComparative foot morphologyComparative foot morphology is exemplified through study of the form of distal limb structures of a variety of terrestrial vertebrates. A challenge to understanding the role of the feet of a variety of different organisms is the wide range of body types, foot shapes, arrangement of structures,...