Biomechanics Lab 4 & 5

What kind of lever system is acting on the hip joint during unilateral stance?

*First class lever* The hip joint is the fulcrum, the gluteus medius the effort force, and HAT-L the resistance force

Think about your vertebral column while using your laptop. Discuss the position of your: cervical spine thoracic spine lumbar spine pelvis

-*C-spine*: Typically, it loses some of its normal lordotic curvature, especially if the individual has a forward head posture -*T-spine*: Typically, it becomes more kyphotic. It tends to round out -*L-spine*: Typically, it loses its normal lordotic curvature and becomes flatter -*Pelvis*: Tends to go into a posterior tilt

Describe one strategy that may be helpful to correct deviation of head, shoulders, hips, and, one factor that you cannot change:

-Alignment of the head: stretching out the upper trapezius and levator scapulae -Alignment of the shoulders: see above, strengthening scapular stabilizers and middle/lower trapezius -Alignment of the hips: stretching out hip flexors, hamstrings -Factors that can't be changed: leg length discrepancy, scoliosis, hip anteversion or retroversion, hip angle of inclination

Discuss two environmental modifications that would be appropriate for this client to optimize her safety and independence:

-Be sure to remove any loose objects from the floor like throw rugs, dog toys, etc. -Try and minimize stairs or uneven walking surfaces -Be sure that the home environment has adequate lighting -Encourage your client to wear anti-slip socks while in the house, or shoes with rubber soles to minimize slips

transfers: Have your partner lean back in the chair with their pelvis forward

-Your COM moves anterior -Your partner's COM moves posterior -Discomfort potentially because of the rounded out vertebral column

transfers: Stand close to your partner with your knees bent and feet behind your knees.

-Your COM moves anterior to your BOS with your feet behind your knees -Your partner's COM potentially moves more posterior -You could have discomfort in your lumbar and thoracic spine if your vertebral column is rounded out.

transfers: Stand farther away with your knees straight and your trunk flexed toward your partner

-Your COM moves way too far forward -Your partner's COM again moves potentially farther back -Discomfort in the vertebral column, especially the thoracic and lumbar areas

transfers: Have your partner lean into you with their trunk flexed and feet behind their knees

-Your COM will move posterior -Your partner's COM will be too far forward -You could have discomfort if you fire your erector spinae forcefully with attempts to transfer the client

You just accepted your first job at St. Joe's Hospital in inpatient rehab. Identify 3 exercises that would help you reduce your chances of injury to your spine (you will be doing a lot of transfers and lifting). Include your rationale in the answers.

1. *Sit ups*: This helps to condition your abdominals and hip flexors 2. *Squats*: This helps to strengthen your quadriceps, hamstrings, and gluteus maximus 3. *Back extension exercises*: remember to do these from full extension to only about 1/3 the way down towards flexion

force vectors involved in unilateral stance

1. Gluteus medius from origin to insertion 2. Ground reaction force from the ground to the hip joint 3. HAT-L (head, arms, trunk and upper limb on unsupported side) 4. Adduction torque from medial pelvis to femur 5. Gravity through middle of pelvis

Discuss factors that you can change in order to effect positive change on your spine while sitting at your desk, in the classroom, or at your kitchen table:

1. Position the computer at eye level. This positions the head in alignment with your COM and favors more normal posture of your vertebral column 2. Place a lumbar roll on your chair to encourage anterior pelvic tilt 3. Place a phone book or small stool under your feet to keep your hips and knees at approximately 90 degrees

Discuss: 1. How each of the following changes as an infant develops, and 2. Provide an example of a factor that can adversely affect these changes: hip joint

1. The hip has a large angle of inclination and anteversion at birth. The angle of inclination gets smaller in response to weight bearing, and the degree of anteversion lessens as well 2. Normal orientation of the femoral head in the acetabulum can be adversely affected with lack of normal weight bearing and ambulation as a child develops. The degree of anteversion may remain high, and the child can compensate by medially rotating their hips while they sit (frog sitting) or stand/walk (toe in walking).

Discuss: 1. How each of the following changes as an infant develops, and 2. Provide an example of a factor that can adversely affect these changes: vertebral column

1. The vertebral column is initially entirely kyphotic at birth. The cervical spine develops more lordosis in response to head control/extension against gravity. The lumbar spine similarly develops lordosis in response to weight bearing, upright sitting/standing. 2. A child with hypotonia, such as seen with CP, can adversely affect development of the secondary cervical and lumbar curves due to inability to lift the head against gravity, sit or stand.

You are reviewing discharge instructions with your client who has hip osteoarthritis. Describe your instructions with the following: carrying objects

Always try to carry objects on the same side as your painful hip. This helps your muscles around your hip to work with less effort (the moment created by the object is closer to the hip joint so the gluteus medius does not have to contract as strongly. This helps to reduce the compressive forces on the hip).

how does COM change with hip flexion contracture

COM falls anterior to the hip joint. Normally it falls just posterior to the hip axis

how does COM change with knee flexion contracture

COM falls posterior to the axis of the knee. It normally falls just behind the patella. This causes more force output required of the quadriceps during quiet standing.

how does COM change with weak hip and trunk extensor muscles

COM falls too fall forward

Describe how our posture changes as we age:

Collectively our thoracic spine becomes more kyphotic, and our cervical and lumbar spine become less lordotic. Our muscles also atrophy and weaken due to sarcopenia.

Describe how forces are altered with: obesity

Excess weight increases overall HAT-L and therefore creates more force that the gluteus medius must overcome. This can crate excessive compressive forces on the hip joint

Stand on one foot. What external moments does your body have to counteract in order to maintain your balance?

External moments: HAT-L, gravity, ground reaction force on the stance leg

Describe each of the following altered vertebral column positions and discuss one potential reason why these may occur: reduced lordosis of L spine

Flattened or straight back. Individuals who have tight hamstrings tend to have more posterior tilt, and this can cause the lumbar spine to straighten.

Lift a load in the classroom using each of the following and describe the forces acting on the vertebral column: a stoop lift

Forces are applied to the soft tissues surrounding the vertebral column. Very little force is transferred to the lower limbs or hips. The knees are not flexed sufficiently to allow the quadriceps and hamstrings to take the load.

intervention options for forward head and rounded vertebral column

Forward head: strengthening cervical flexors to encourage chin tuck, stretching pectoralis major and minor, focusing on scapular retraction and posterior tilt. Rounded vertebral column: strengthening trunk extensors, gluteus maximus, cervical extensors

What should you tell your client to do with the castors on their wheelchair if they need to adjust their footrests/lower extremities?

I would recommend adjusting the castors so they are facing in the front. This helps to lengthen the base of support of the wheelchair and optimizes stability and security of the chair. This also prevents the w/c from tipping forward as the client reaches down towards the footrests.

transfers: Change the position of both yours and your partner's feet (close together, far apart)

If your feet and your client's feet are far away from each other, then the BOS is potentially too wide and can become unstable. If your feet and your client's feet are too close together, then the BOS is potentially too small and the COM of you and your client may not fall within that BOS,, making it a potentially unstable situation.

Describe the position of the wheelchair castors when the wheelchair is moving: in a forward direction in a backward direction

In a forward direction: The castors move towards the back of the wheelchair In a backward direction: The castors move toward the front of the wheelchair

What internal moments are created to allow you to continue standing?

Internal moments: gluteus medius contraction on the stance leg, adduction torque on stance leg, gastrocnemius and soleus contraction on the stance leg

Describe how forces are altered with: leaning toward painful/affected hip while walking

Leaning toward the painful side helps to reposition HAT-L closer to the axis of the hip joint. This then reduces the moment or torque created by HAT-L, and in response the gluteus medius does not have to contract as strongly to keep the pelvis level. This then reduces the compression forces on the hip joint.

Describe two OT interventions you can implement for an individual with osteoporosis and significant thoracic kyphosis:

Modify the environment so the individual can interact with everything close to their COM. This is important because they are at more of a fall risk because their COM is too anterior Also introduce adaptive devices to optimize standing and sitting balance such as grab bars, raised toilet seat, shower bench, recommend rubber soled slippers and shoes, good lighting, etc.

Describe how forces are altered with: carrying a heavy suitcase on the unaffected side

Placing the weight of the suitcase on the opposite side to the painful hip increases HAT-L. This then forces the gluteus medius to contract more strongly to keep the pelvis level during ambulation. This can create more compressive forces on the hip and increases the demands on the gluteus medius.

Describe each of the following altered vertebral column positions and discuss one potential reason why these may occur: excess lordosis of L spine

Pregnancy, individuals who have a large stomach or those that have excessive anterior tilt of the pelvis

Identify factors that YOU can change in order to reduce forces placed on your lumbar spine w backpack:

Reduce the weight!! Change where the load is in relation to your vertebral column. A rolling pack works great, along with carrying your books in front and close to your body. Or, have your books on a tablet

Describe each of the following altered vertebral column positions and discuss one potential reason why these may occur: excess kyphosis of T spine

Rounding out of the vertebral column such as reaching in the oven to take out a big turkey at Thanksgiving. This can occur when a load is placed in front of the vertebral column, and the upper limbs are in an outstretched position.

Describe each of the following altered vertebral column positions and discuss one potential reason why these may occur: reduced lordosis of C spine

Someone with excessive forward head. This can cause the cervical spine to flatten out.

Visualize your partner going from a sitting to a standing position with the aid of a raised toilet seat and grab bars on either side of them. What effect did the adaptive equipment have on sit to stand function?

The adaptive equipment makes a dramatic difference in the force demands of the quadriceps, hamstrings, and gluteal muscles when performing sit to stand, or stand-sit function. Because of this, it makes this task much safer with clients who have weakness or are elderly and have sarcopenia as a result of aging. The grab bars transfer the force demands to the UEs and trunk (closed chained movement) also.

You are reviewing discharge instructions with your client who has hip osteoarthritis. Describe your instructions with the following: using her cane

The cane should be used on the unaffected side. This helps to reduce the muscle forces on the painful side needed to ambulate safely and with less discomfort. The cane plus the upper limb/hand on the cane creates a large lever arm, which reduces the force output of the gluteus medius during gait. Always be sure to step with your unaffected leg and the cane at the same time

why do the castors move?

The castors move to optimize the wheelchair base of support in relation to the base of support of the person in the chair.

Lift a load in the classroom using each of the following and describe or illustrate the forces acting on the vertebral column: a squat lift

The forces are applied to the quadriceps, hamstrings, gluteus maximus and iliopsoas (also the gastrocnemius). The erector spinae as able to contract effectively due to the neutral position of the vertebral column.

Discuss how your hip and trunk extensor muscles work together to perform the following activities: bring yourself back up to an upright position

The gluteus maximus and hamstrings contract concentrically, along with the erector spinae to bring you back up to an upright position

What is holding pelvis stable/level when you walk?

The gluteus medius and minimus on the stance leg

Describe force couple that acts on your pelvis to produce: posterior tilt

The hamstrings pull the pelvis down, and the abdominals pull up, creating a posterior tilt.

How are these muscle forces altered if you are wearing high heeled shoes?

The heel repositions our COM farther forward. This then causes a flexion moment that the erector spinae, gluteus maximus, hamstrings and gastrocnemius must overcome to maintain equilibrium.

Describe force couple that acts on your pelvis to produce: anterior tilt

The ilipsoas pull the pelvis down, and the erector spinae pulls it up, creating an anterior tilt

rise from a chair with feet: 1. close together, 2. shoulder width apart and, 3. far apart: Which one(s) are the most difficult? Why

The more difficult ones are 1. and 3. (theoretically at least). I know it is difficult to sense this on yourselves, since you have normal muscle tone and function. That said, the position of the feet will change where your COM falls when you bring your trunk forward to stand, and it will change the size of your base of support.

Describe how the muscle force(s) are different if sit-to-stand from HIGH surface

The muscles force demands are dramatically reduced if the sitting surface is high. This is directly proportional to the degree of hip flexion that the client is in. The less hip flexion, the less overall force demands placed on the muscles stated in previous question. Additionally, less hip flexion places the quads and hamstrings at a more optimal resting length; thereby reducing the force demands placed on them.

What muscles have to produce adequate force in order to perform sit to stand from a LOW surface?

The primary muscles needed for this task are the gluteus maximus, hamstrings as a group, and the quadriceps. The gastrocnemius and soleus are important also, along with the erector spinae.

Why would an individual with quadriceps weakness have difficulty with the squat lift?

The quadriceps would not be able to contract concentrically with enough force to overcome the load being lifted. The individual may substitute by rounding the vertebral column out or trying to recruit the erector spinae more to overcome the load.

Where should your client place their seatbelt to encourage proper pelvic positioning in their wheelchair? Explain why this is important.

The seat belt should be placed over the client's hips and pelvis, not their abdomen. This is important because a belt placed across the stomach can encourage posterior pelvic tilt and cause the hips and pelvis to move forward in the wheelchair. This can then cause unwanted shear forces on the ischial tuberosities, and loss of optimal vertebral column alignment.

is a stoop or a squat lift better?

The squat lift is theoretically better because the vertebral column is in neutral alignment, and the erector spinae, quadriceps, hamstrings, and hip extensor muscles can create optimal force to equalize the load created by the box/whatever is being lifted. However, this type of lift creates excessive compressive forces on the knees, so it is best to avoid full flexion of the knees to minimize these forces.

Describe how your body reacts to equalize the forces created by the weight of your backpack on your back while you walk to class:

The weight of the backpack creates an extension moment near your lumbar and thoracic spine. In response to this moment, the abdominal muscles and hip flexors contract to equalize the forces.

Describe why your low back is prone to injury if: you carry all of your textbooks in your backpack

The weight of the textbooks creates a large extension moment that your body has to overcome. It does this by trying to contract your abdominals and hip flexors. This is OK for short periods, but the weight of the backpack adds considerable compressive forces to your vertebral bodies, especially the lumbar area. This in turn can cause nerve root compression, pain, and arthritic changes over time.

Muscle forces generated in quiet standing

There is minimal muscle activity in quiet standing. The gastrocnemius, ilipsoas, and a bit of erector spinae are all the muscle forces that are acting on our bodies when we stand.

Discuss why an individual with a hip flexion contracture would tire easily when standing:

This alters where the COM normally falls in quiet standing, creating a flexion moment. In response, the hip and trunk extensors must activate more to maintain equilibrium.

Stand with your feet together. Have your partner push you very lightly backwards, then forward. Which muscle(s) did you engage for you to maintain your balance:

When you were pushed from the front of your body: *the tibialis anterior primarily* When you were pushed from the back of your body: *the gastrocnemius and soleus*

Describe why your low back is prone to injury if: your core musculature is deconditioned

Your core cannot respond to the large extension moment created by the textbooks and places more loads on the vertebral column and soft tissues in response.

Discuss how your hip and trunk extensor muscles work together to perform the following activities: bend over to pick up your backpack at the end of class

Your gluteus maximus and hamstring muscles contract eccentrically along with your erector spinae at the beginning of trunk flexion. At about halfway down the soft tissues surrounding your vertebral column take over to control your trunk as you get closer to the ground

where does COM of vertebral column fall

on the concave side of the C, T, L curves