Chapter 3 Understanding Human movement Impairments

Question 1

Learning Objectives

Answer 1

Upon completion of this chapter, you will be able to:

• Explain the importance that proper posture has on movement.
• Understand and explain common causes of movement dysfunction.
• Understand and explain common human movement system dysfunctions and potential causes for each.

Question 2

Neuromuscular Efficiency

Answer 2

The ability of the NS to allow agonists, antagonists, and stabilizers to work synergistically to produce, reduce and dynamically stabilize the HMS in all 3 planes fo motion

Question 3

Functional Efficiency

Answer 3

The ability of the NS to recruit correct muscle synergies at the right time, with the appropriate amount of force to perform functional tasks with the least amount of energy & stress on the HMS

Question 4

Structural Efficiency

Answer 4

The alignment of each of the HMS which allows posture to be balanced in relation to one’s center of gravity.

Question 5

Posture

Answer 5

The independence &interdependent alignment (static posture) & functional (transitional & dynamic posture) of all components of the HMD at any given moment, controlled by CNS

Question 6

Cumulative injury cycle

Answer 6

A Cycle whereby an injury will induce inflammation, muscle spasm, adhesions, altered neuromuscular control, and muscle imbalances

Question 7

Movement impairment syndromes

Answer 7

Refer to the state in which the structural integrity of the HMS is compromised because the components are out of alignment.

Question 8

Optimal neuromuscular efficiency

Answer 8

Question 9

Human movement impairment

Answer 9

Question 10

Joint Dysfunction

Answer 10

Hypomobility

Altered length-tension relationship

Altered force-couple relationships

Altered movement

Structural and functional inefficiency

Question 11

Altered reciprocal inhibition

Answer 11

The process whereby a tight muscle (short, overactive, myofascial adhesions) causes decreased neural drive, and therefore optimal recruitment of its functional antagonist.

Question 12

Synergistic dominance

Answer 12

The process by which a synergist compensates for a prime mover to maintain force production.

Question 13

Lower extremity movement impairment syndrome

Answer 13

Usually characterized by excessive foot pronation (flat feet), increased knee valgus (tibia internally rotated and femur internally rotated and adducted or knock-kneed), and increased movement at the LPHC (extension or flexion) during functional movements.

Question 14

Upper extremity movement impairment syndrome.

Answer 14

Usually characterized as having rounded shoulders and a
forward head posture or improper scapulothoracic or glenohumeral kinematics during functional movements.

Question 15

Static Malalignments (altered length-tension
relationships or altered joint arthrokinematics)

Answer 15

Common static malalignments of the foot and ankle include hyperpronation of the foot ( 9, 20, 51, 52 ), which may result from overactivity of the peroneals and lateral gastrocnemius, under activity of the anterior and posterior tibialis, and decreased joint motion of the first metatarsophalangeal (MTP) joint and talus (decreased posterior glide). It has been reported that there is decreased ankle dorsiflexion after an ankle sprain ( 53, 54 ). It is hypothesized that decreased posterior glide of the talus can decrease dorsiflexion at the ankle

Question 16

Abnormal Muscle Activation Patterns
(altered force-couple relationships)

Answer 16

It has been demonstrated that subjects with unilateral chronic ankle sprains had weaker ipsilateral hip abduction strength ( 17, 19 ) and increased postural sway ( 58, 59 ). It has also been demonstrated that subjects with increased postural sway had up to seven times more ankle sprains than those subjects with better postural sway scores

Question 17

Dynamic Malalignment

Answer 17

It has been shown that excessive pronation of the foot during weight-bearing causes altered alignment of the tibia, femur, and pelvic girdle ( Figure 3. 5 ) and can lead to internal rotation stresses at the lower extremity and pelvis, which may lead to increased the strain on soft tissues (Achilles’ tendon, plantar fascia, patella tendon, IT-band, etc.) and compressive forces on the joints (subtalar joint, patellofemoral joint, tibiofemoral joint, iliofemoral joint, and sacroiliac joint), which can become symptomatic ( 9, 51 ). The LPHC alignment has been shown by Khamis and Yizhar ( 66 ) to be directly affected by bilateral hyperpronation of the feet. Hyper pronation of the feet induced an anterior pelvic tilt of the LPHC. The addition of two to three degrees of foot pronation led to a 20 to 30% increase in pelvic alignment while standing and a 50 to 75% increase in anterior pelvic tilt during walking ( 66 ). Because anterior pelvic tilt has been correlated with increased lumbar curvature, the change in foot alignment might also influence lumbar spine position ( 67 ). Furthermore, an asymmetric change in foot alignment (as might occur from a unilateral ankle sprain) may cause asymmetric lower extremity, pelvic,
and lumbar alignment, which might enhance symptoms or dysfunction.

Question 18

Hip and Knee
Scientific Review

Answer 18

Knee injuries account for greater than 50% of injuries in college and high school ( 25, 26 ) athletes, and among lower extremity injuries, the knee is one of the most commonly injured segments of the HMS. Two of the more common diagnoses resulting from physical activity are patellofemoral pain (PFP) and ACL sprains or tears. Both PFP and ACL injuries are public health concerns costing $2.5 billion annually for ACL injuries ( 38 ). Most knee injuries occur during noncontact deceleration in the frontal and transverse planes ( 43, 68 ). It has also been shown that static malalignments, abnormal muscle activation patterns, and dynamic malalignment alter neuromuscular control and can lead to PFP ( 14, 24 ), ACL injury ( 47, 69 – 74 ), and IT-band tendonitis

Question 19

Static Malalignments (altered length-tension
relationships and joint arthrokinematics)

Answer 19

Static malalignments can lead to increased PFP and knee injury.

Common static malalignments include hyperpronation of the foot ( 9, 20, 51, 52 ), increased Q-angle (a 10-degree shift in Q-angle increased patellofemoral contact forces by 45%) ( 75 ) Figure 3. 9, anterior pelvic tilt ( 66 ), and decreased flexibility of the quadriceps, hamstring complex, and iliotibial band ( 21, 22, 27 )

Question 20

Abnormal Muscle Activation Patterns
(altered force-couple relationships)

Answer 20

Abnormal muscle activation patterns can lead to PFP, ACL injury, and other knee
injuries. Abnormal contraction intensity and onset timing of the vastus medialis
obliquus (VMO) and vastus lateralis have been demonstrated in subjects with PFP

See pg 72 for more

Question 21

Dynamic Malalignments

Answer 21

Dynamic malalignments may occur during movement as a result of poor
neuromuscular control and dynamic stability of the trunk and lower extremities ( 14, 70, 84, 85 ). Static malalignments (altered length-tension relationships and altered joint arthrokinematics) and abnormal muscle activation patterns (altered force- couple relationships) of the LPHC compromise dynamic stability of the lower extremity and result in dynamic malalignments in the lower extremity ( 83, 84 ). Th ere is a consistent description of this dynamic malalignment (multisegmental HMS impairment) as a combination of a contralateral pelvic drop, femoral adduction and internal rotation, tibia external rotation, and hyper pronation ( 9, 14, 70, 73, 85 – 92 ) Figure3.6 )

Question 22

Dynamic Malalignments Part2

Answer 22

This multisegmental dynamic malalignment (movement impairment syndrome) has been shown to alter force production ( 94 ), proprioception ( 95 ), coordination ( 96 ), and landing mechanics ( 97 ). Defi cits in neuromuscular control of the LPHC may lead to uncontrolled trunk displacement during functional movements, which in turn may place the lower extremity in a valgus position, increase knee abduction motion and torque (femoral adduction or internal rotation and tibial external rotation occurring during knee flexion), and result in increased patellofemoral contact pressure ( 75, 98 ), knee ligament strain, and ACL injury ( 70, 85 ).

Question 23

Low Back
Scientific Review

Answer 23

Back injuries can be costly to both the individual and the health-care system. Previous studies have found a high incidence of low-back pain (LBP) in sports ( 99 – 101 ). For example, 85% of male gymnasts, 80% of weightlifters, 69% of wrestlers, 58% of soccer players, 50% of tennis players, 30% of golfers, and 60 to 80% of the general population were reported to have LBP ( 102 – 104 ). It is estimated that the annual costs attributable to LBP in the United States are greater than $26 billion per year ( 105 ).

Question 24

Low Back
Scientific Review

part 2

Answer 24

Individuals who have LBP are significantly more likely to have additional low-back injuries, which can predispose the individual to future osteoarthritis and long-term disability ( 106 ). It has been demonstrated that static malalignments (altered length-tension relationships or altered joint arthrokinematics), abnormal muscle activation patterns (altered forcecouple relationships), and dynamic malalignments (movement system impairments) can
lead to LBP.

Question 25

**Static Malalignments** (altered length-tension relationships or altered joint arthrokinematics)

Answer 25

Optimal muscle performance is determined by the posture (length-tension) of the LPHC during functional activities ( 107 – 110 ). If the neutral lordotic curve of the lumbar the spine is not maintained (i.e., low-back arches, low-back rounds, or excessive lean forward), the activation ( 107 ) and the relative moment arm of the muscle fibers decreases ( 109, 110 ). Vertebral disk injuries occur when the outer fibrous structure of the disk (annulus fibrosis) fails, allowing the internal contents of the disk (nucleus pulposus) to be extruded and irritate nerves exiting the intervertebral foramen Figure 3. 11. The exact mechanism underlying injury to the intervertebral disk is unclear, but it is generally proposed that it is caused by a combination of motion with compressive loading.

Question 26

**Static Malalignments (altered length-tension relationships or altered joint arthrokinematics)** **(cont)**

Answer 26

In addition, a combination of motions about the lumbar spine has been demonstrated to increase the strain placed on the disks, and include flexion with lateral bending ( 112 ). This combination of motions may generate an axial torque that Drake et al. ( 113 ) demonstrated to increase the initiation of disk herniation ``` . Lu et al. ( 114 ) combined all of these factors and were able to demonstrate that compression combined with bending and twisting moments about the disk contributed to earlier degeneration in saturated intervertebral disks. Pelvic asymmetry (iliac rotation asymmetry or sacroiliac joint asymmetry) Figure 3. 12 has been shown to alter the movement of the HMS in standing ( 115 ) and sitting ( 116 ). Pelvic asymmetry alters the static posture of the entire LPHC, which alters normal arthrokinematics (coupling movement of the spine) ( 117 – 119 ). ```

Question 27

**Abnormal Muscle Activation Patterns (altered force-couple relationships)**

Answer 27

Because the LPHC musculature plays a critical role in stabilizing this complex, the insufficiency of any of the musculature may induce biomechanical dysfunction and altered force-couple relationships ( 122 ). Subjects with LBP have been reported to demonstrate impaired postural control ( 123 – 125 ), delayed muscle relaxation ( 126, 127 ), and abnormal muscle recruitment patterns ( 128 ), notably the transverse abdominis and multifidus activation is diminished in patients with LBP ( 129, 130 ). A similar delay inactivation of the internal oblique, multifidus, and gluteus maximus was observed on the symptomatic side of individuals with sacroiliac joint pain ( 131 ). Hides et al. ( 132 ) demonstrated that multifidus atrophy was present in clients even in the absence of continued LBP. Further, Iwai et al. ( 133 ) demonstrated that trunk extensor strength was correlated with LBP in collegiate wrestlers.

Question 28

**Abnormal Muscle Activation Patterns (altered force-couple relationships)** **(cont)**

Answer 28

Nadler et al. ( 134 ) demonstrated that a bilateral imbalance in the isometric strength of the hip extensors was related to the development of LBP. The loads, forces, and movements that occur about the lumbar spine are controlled by a considerable number of ligaments and muscles. The ligaments that surround the spine limit intersegmental motion, maintaining the integrity of the lumbar spine. These ligaments may fail when proper motion cannot be created, proper posture cannot be maintained, or excessive motion cannot be resisted by the surrounding musculature ( 107 – 110 ). Therefore, decreasing the ability of local and global stabilizing muscles to produce adequate force can lead to ligamentous injury Figure 3. 13.

Question 29

**Dynamic Malalignments**

Answer 29

Decreased core neuromuscular control may contribute to increased valgus positioning of the lower extremity, which can lead to increased risk of knee injuries ( 84, 135 ). Several studies have demonstrated that training of the trunk musculature may increase the control of hip adduction and internal rotation during functional activities and prevent dynamic malalignments and the potential injuries that arise from this impaired movement pattern ( 136 – 138 )

Question 30

**Shoulder Scientific Review**

Answer 30

Shoulder pain is reported to occur in up to 21% of the general population ( 139, 140 ) with 40% persisting for at least one year ( 141 ) at an estimated annual cost of $39 billion ( 142 ). Shoulder impingement is the most prevalent diagnosis, accounting for 40 to 65% of reported shoulder pain ( 143 ), while traumatic shoulder dislocations account for an additional 15 to 25% of shoulder pain ( 144 – 146 ). The persistent nature of shoulder pain may be the result of degenerative changes to the shoulder’s capsuloligamentous structures, articular cartilage, and tendons as the result of altered shoulder mechanics.

Question 31

**Shoulder Scientific Review** **(cont)**

Answer 31

As many as 70% of individuals with shoulder dislocations experience recurrent instability within two years ( 146 ) and are at risk of developing glenohumeral osteoarthritis secondary to the increased motion at the glenohumeral joint ( 147, 148 ). Degenerative changes may also affect the rotator cuff by weakening the tendons with time through intrinsic and extrinsic risk factors ( 142, 149 – 151 ), such as repetitive overhead use (\>60 degrees of shoulder elevation), increased loads raised above shoulder height ( 152 ), and forward head and rounded shoulder posture ( 153 ), as well as altered scapular kinematics and muscle activity ( 154, 155 ). Those factors are theorized to overload the shoulder muscles, especially the rotator cuff, which can lead to shoulder pain and dysfunction. Given the cost, rate of occurrence, and difficult resolution of shoulder pain, preventive exercise solutions that address these factors are essential in preventing shoulder injuries. It has been demonstrated that static malalignments (altered length-tension relationships or altered joint arthrokinematics), abnormal muscle activation patterns (altered force- couple relationships), and dynamic malalignments (movement system impairments) can lead to shoulder impairments ( 154 – 158 ).

Question 32

**Static Malalignments (altered length-tension relationships or altered joint arthrokinematics)**

Answer 32

It has been demonstrated that posterior glenohumeral capsular contracture can alter normal glenohumeral kinematics, resulting in increased anterior and superior migration of the humeral head during shoulder flexion and significantly limiting shoulder internal rotation ( 159, 160 ). It is also theorized that rounded shoulders (forward shoulder posture) ( Figure 3. 7 ) alters the normal length-tension relationship and joint kinematic balance of the shoulder complex ( 161 ). Any kinematic mechanism that reduces the subacromial space during humeral elevation will likely predispose an individual to impingement of the rotator cuff ( 162 – 164 ).

Question 33

**Abnormal Muscle Activation Patterns (altered force-couple relationships)**

Answer 33

Rounded shoulder posture lengthens the rhomboids and lower trapezius musculature and shortens the serratus anterior, which alters the normal scapulothoracic forcecouple relationship. This altered posture and muscle recruitment pattern would cause the scapula to remain forward-tipped and internally rotated relative to the elevating humerus, forcing the acromion and humerus to approximate and narrow the subacromial space ( 161, 165, 166 ) Figure 3. 14. Furthermore, a rounded shoulder posture may lead to decreased rotator cuff activation, which would decrease stabilization and lead to compression of the humeral head in the glenoid fossa ( 155, 166 ).

Question 34

**Dynamic Malalignments**

Answer 34

There is a sequential muscle activation and force development pattern that is initiated from the ground to the core and through the extremities that have been demonstrated during kicking, running, and throwing and with a tennis serve ( 167– 169 ). It has been demonstrated that approximately 85% of the muscle activation required to slow the forward-moving arm while throwing comes from the core and the scapulothoracic stabilizers ( 170 ). It has also been shown that maximal rotator cuff activation can be increased by 23 to 24% if the scapula is stabilized by the core musculature and the scapulothoracic stabilizers (trapezius, rhomboids, serratus anterior(171 ).

Question 35

**Dynamic Malalignments** **(cont)**

Answer 35

A recent study demonstrated a significant decrease in shoulder internal rotation (9.5 degrees), total shoulder motion (10.7 degrees), and elbow extension (3.2 degrees) immediately after pitching a baseball in the dominant shoulder. These changes continued to exist 24 hours after pitching ( 172 ). Altered static posture, muscle imbalances, and muscle weakness in the lower extremity, LPHC, or upper extremity can lead to dynamic malalignments.

Question 36

**Chapter 3 summary**

Answer 36

The HMS consists of the myofascial system, articular system, and neural system. Each system functions synergistically. Dysfunction in any system alters length-tension relationships, force-couple relationships, and joint kinematics, leading to movement impairment syndromes. The health and fitness professional must understand these concepts and the importance of maintaining proper structural and functional efficiency during training, reconditioning, and rehabilitation. The health and fitness professional must also be capable of performing a comprehensive HMS assessment before initiating a training program.