Read this article to learn about the movement along the demand curve: When quantity demanded of a commodity changes due to a change in its price, keeping other factors constant, it is known as change in quantity demanded. It is graphically expressed as a movement along the same demand curve. There can be either a downward movement Expansion in demand or an upward movement Contraction in demand along the same demand curve.
Two specific patterns to be discussed are Hip Extension and Hip Abduction 1.
Hip extension and hip abduction movement patterns involve specific muscles. The muscles involved in the movements are gluteus maximus, gluteus medius, psoas, quadratus lumborum, erector spinae, piriformis, TFL, biceps femoris, adductors and rectus femoris. The synergist assists the agonist during the movement.
The antagonist acts in opposition to the agonist and moves the joint into the opposite direction of the action of the agonist. Any deviation from the specific muscle activation is considered an altered movement pattern. This will cause hip extension dysfunction, muscle imbalance, pain and contribute to changes in posture.
The normal sequence of muscular contractions for hip extension involves the contraction of the gluteus maximus and the ipsilateral biceps femoris, followed immediately by the contraction of the contralateral opposite side erector spinae and then the ipsilateral erector spinae.
The gluteus maximus is the primary muscle responsible for the motion of hip extension. The ipsilateral biceps femoris assists during gait by flexing the knee.
Immediately after the contraction of these two muscles, the contralateral side erector spinae muscle contracts, followed by the contraction of the ipsilateral erector spinae muscle to help stabilize the lumbar spine and pelvis allowing movement of the hip during gait.
A change often seen in altered hip extension movement is the contraction of the ipsilateral erector spinae muscle before the gluteus maximus muscle contracts, to initiate the movement of hip extension.
This can be observed with the patient prone and performing hip extension. When this occurs, the erector spinae becomes the primary muscle initiating hip extension. Weakness of the gluteus maximus prevents itself from functioning as the primary muscle initiating hip extension.
What can cause an altered hip extension movement? Weakness or inhibition of the gluteus maximus can be the result of an injury to the muscle, deconditioning as a result of an illness or injury limiting the activity of walking, overuse due to excessive repetitive motion or overactivity of an antagonistic muscle.
The gluteus maximus muscle will display signs of a weakened contraction, flattened shape and triggers points be found in the muscle. The psoas muscle, a hip flexor and an antagonist muscle of gluteus maximus, is often another cause of altered hip extension.
Tightness or hypertonicity of the psoas muscle resulting from prolonged sitting in a flexed position can mechanically restrict the motion of hip extension.
A tight psoas muscle will restrict hip extension range of motion, which normally is 20 degrees, and will result in a decreased stride. Tightness of the psoas can also cause postural changes in the lumbar spine by decreasing the lumbar lordosis. The rectus femoris muscle also functions as an antagonistic muscle to gluteus maximus since it also assists in hip flexion.
Together, the action of the psoas and the rectus femoris, can mechanically inhibit hip extension range of motion. Weakness in the gluteus maximus muscle will cause recruitment of a synergistic muscle, the erector spinae to initiate hip extension.
The erector spinae will contract on the ipsilateral side of hip extension before contraction of the gluteus maximus to initiate hip extension and stabilize the pelvis. As a result, the erector spinae muscle acts as the primary muscle, initiating hip extension replacing the gluteus maximus.
This will cause an increase in the stress on the lumbar spine. The erector spinae will also become hypertonic, causing an increase in the stress load on the lumbar facet.
Pain in the lumbar spine increasing while walking will also be a symptom along with decreased passive and active ranges of motion of hip extension. Altered hip extension can occur unilaterally or bilaterally.
Along with mechanical inhibition of the gluteus maximus, a neurological inhibition will occur because of the change in sequence in muscle activation.
The new neurological sequence or pathway initiating hip extension will be stored in the cerebellum, which will also inhibit activation of the gluteus maximus. The gluteus medius muscle is the primary muscle responsible for hip abduction.
The synergist muscles are the psoas, piriformis, TLF, quadratus lumborum and rectus femoris. The hip adductor muscles are the antagonists to the glutues medius. Hip abduction involves the contraction of the gluteus medius, causing a smooth lateral abduction of the lower extremity away from the body.
Changes in the movement will occur when the gluteus medius muscle can not initiate and perform hip abduction by itself. Conditions that can weaken or inhibit the gluteus medius muscle include an injury to the muscle, deconditioning due to an illness or injury limiting the activity of walking, overuse due to excessive repetitive motion and overactivity of an antagonist.
The causes are the same types of causes associated with causing hip extension dysfunction. Hip hiking is the raising of the pelvis on the side of the body during gait movement caused by the premature contraction of the quadratus lumborum muscle on the side of hip abduction before contraction of the ipsilateral gluteus medius muscle.
The contraction of the quadratus lumborum muscle initiates the sequence of hip abduction. This will occur when gluteus medius is not strong enough or is inhibited in intiating the movement of hip abduction. Hip hiking can be observed while the patient is walking.Figure 1: A demonstration of the difference in force responses for between lengthening and non-lengthening active contractions (isometric vs.
eccentric), and between active lengthening (eccentric) vs. non-active lengthening (passive stretch). The complete, origianl text of the VA's Schedule for Rating Disabilities.
Contraction risk and extension risk are components of prepayment risk of a pass-through security. Contraction risk is the risk that the average life of the security will decrease because of a fall in interest rates.
Extension risk is the risk that the average life of the security will increase because of an increase in interest rates. 5. Relationships between maximal torque and intra-abdominal pressure (IAP) during maximal voluntary isometric hip extension (a) and flexion (b) in inspiratory condition (black closed circle), normal condition (gray closed circle), and expiratory condition (open circle).
during ﬁve different knee-extension contraction rates Blood ﬂow and oxygen uptake increase with total power during ﬁve different knee-extension contraction rates. probably due to the difference in nature of these activ-ities: during running and walking horizontally on a. Distinguish between an extension and a contraction and an increase and a decrease in supply and demand.
What factors may cause such changes?. (, July 22).5/5(1).