Foundational Sciences

Question 0

Describe the components of a sarcomere.

Answer 0

A-bands: “anisotropic” dark areas of myosin
I-bands: “isotropic” actin
M-line: proteins in the middle of myosin
Z-line: ends of actin
H zone: central portion of a-band where there is no overlap

Question 1

Describe the components of a muscle.

Answer 1

Sarcomere>myofibril>myofiber>fascicles

Question 2

Explain the sliding filament theory.

Answer 2

Muscles contract by actin fibers and myosin fibers sliding past each other due to an action potential.

Question 3

Describe a muscular contraction.

Answer 3

AP propagates down alpha motor neuron to a motor end plate. ACh is released to receptors on the muscle fiber, setting off an AP in the cell. This causes calcium in the sarcoplasmic recticulum to release. Ca binds with C-troponin, allowing myosin-actin cross bridging to occur. A ratcheting action causes contraction.

Question 4

Describe the types of muscle fibers.

Answer 4

Type 1: slow twitch, oxidative, endurance
Type 2: fast twitch, less aerobic, speed and power
Type 1 are smaller cross sectional area. Aside from enzyme and molecular differences, the smaller cross sectional area allows for greater diffusion of oxygen from surrounding capillaries

Question 5

Describe muscle fiber arrangements.

Answer 5

Some are in parallel, such as the sartorius, and develop tension along the axis of the muscle. This allows for greater ROM and quicker action.

Some are pennate, allowing for greater concentrations of muscle fibers and more force development. If the pennate angle remains below 30*, the amount of extra fibers is greater than the force lost due to the fibers not transmitting all of force in line with the tendon, increasing overall force production.

Question 6

How does PRE work?

Answer 6

Increases the amount of ACh released and the number of receptors present, allowing for higher threshold fibers to be activated and therefore more fibers recruited.
Increases the size of sarcoplasmic recticulum and calcium concentrations.
Increases the number of myofibrils (not fibers), increasing the cross sectional area. This is known as hypertrophy.

Question 7

How does endurance training work?

Answer 7

Increases the capillaries around muscle fibers, allowing for greater oxygen diffusion. Increases the oxidative enzymes.

Question 8

Describe GTOs.

Answer 8

Aligned in series with muscle fibers and tendons. Detects change in tension and causes an inhibitory reflex once a certain force is exceeded in order to prevent harmful muscular contraction.

Question 9

Describe muscle spindle fibers.

Answer 9

Arranged in parallel to muscle fibers. This allows them to be stretched when muscles are stretched. They cause an excitatory reflex and increase contraction strength.
They have intrafusal fibers inside that have an efferent gamma neuron, controlled by higher cortex levels, that adjust small contractile fibers at the ends of the spindle and allow for regulation during activity. Afferent neurons are the sensing portion.
There are more spindles in muscles that perform complex movements.

Question 10

How can muscle temperature changes be beneficial?

Answer 10

Can alter the Q10 (ratio of rate of enzymatic action at a given temperature compared to the rate 10C lower), allowing for quicker reactions. Temps above 40C (104) slow the rate of reaction and oxygen utilization.

Question 11

Discuss the convex-concave rule.

Answer 11

This rule was the result of collaboration between Norwegian PT Freddie Kaltenborn and Dr. James Cyriax. The kaltenborn method advocates that the roll and slide of a convex surface on a concave surface are opposite, while the rock and glide of a concave surface on a convex surface are the same direction. This information is incorporated into manual therapy during mobilization techniques. This method may not always hold true however, as demonstrated in a study by Baeyans et al, examining ER at 90* abduction during the throwing motion.

Question 12

Discuss AOR.

Answer 12

In a nonpathologic joint, AOR is usually in the convex portion. A muscles function is governed by its position relative to the AOR. Goniometers should be aligned with AOR.

Question 13

Why is eccentric muscle fictionally important?

Answer 13

Muscle is better able to absorb load than other tissues such as bone or tendons. If strength is too low, higher forces get transmitted to surrounding tissue such as bones, worsening conditions such as OA.

Question 14

Give a functional example of pressure and injury.

Answer 14

Too much pressure can cause bed sores.

In patellofemoral pain syndrome, often the surface area is too small, increasing force at the joint.

Question 15

Describe the forces on bones that cause fractures.

Answer 15

Bone is most resilient against compressive forces, then tension, then shear. When a bone bends, it is usually the curved portion (outside of bend) that fails first. This may not be true in immature bone where tensile strength is higher.

Question 16

Give an example of the clinical implications of the stress-strain curve.

Answer 16

Remember: toe region, elastic region, plastic region, ultimate strength/point of failure.

When testing an injured ligament, if it was not stretched beyond elastic zone it will return to original size and the joint will not be hyper mobile (grade 1). If it went into the plastic zone, some deformation would occur and laxity would be present (grade 2). If it went to failure, it is torn and hyper mobile.

Question 17

Give a clinical example of the importance of length-tension relationship.

Answer 17

A surgically elongated muscle will not be as strong postoperatively.

Question 18

Do tissues adapt at the same rate?

Answer 18

No. For example , muscles have more cells than tendons so they adapt faster. Bone is slower to adapt than muscle. That’s why muscle strength alone is not a good indicator of the rehab process.

Question 19

Discuss holes in bones.

Answer 19

A hole in a bone from a removed screw causes thy bone to be weaker. A hole 20% the diameter of a bone causes it to be 50% weaker. It takes between 4mo and a year for strength to return

Question 20

Describe the cells involved during acute injuries.

Answer 20

Inflammatory phase: leukocytes release Kinins and prostaglandins or serotonin. Serotonin is a strong vasoconstrictor. Prostaglandins sensitize pain receptors, increase vascular permeability, and attract leukocytes.

In the proliferative phase, fibroblasts are most common.

Question 21

Describe nutrition and healing.

Answer 21

Lack of vitamin A and C impair collagen synthesis.

Question 22

How does aging affect healing?

Answer 22

Aging dec metabolic activity, decreases vascular supply, and can impair normal bodily functions.

Question 23

Describe effects of NSAIDS on recovery.

Answer 23

Initially they are beneficial by dec inflammation. This dec tissue deformation and nerve sensitivity. Long term use can be harmful.

Question 24

After repair, when are ligaments strongest and weakest?

Answer 24

Strongest at time of surgery. Strength diminishes by 50% during the first 4-8 weeks. In the next 3-6 months, revascularization and collagen transformation inc strength to about 82% 1yr postoperatively.

Question 25

What are the effects of aging on bone structure?

Answer 25

Weakening occurs due to less efficient hormonal regulation, including dec responsiveness to calcitonin. Agin tissues such as the kidneys and intestine impair calcium absorption and retention. Bones in the elderly are about 50% as strong.

Question 26

How does ultrasound impact bone healing?

Answer 26

Studies show low intensity pulsed US (0.1-0.5 W/cm2) accelerate healing, while higher doses (1.0-2.0) decrease collagen synthesis and protein synthesis.

Question 27

What is the best imaging technique for stress fractures?

Answer 27

MRI (quicker than X-ray, safer than bone scan)

Question 28

Describe spurt vs shunt muscles.

Answer 28

Spurt muscles have their insertions near the joint and a small amount of shortening causes a large change in motion. These are better movers.
Shunt muscles have their origin closer to a joint and are better at stabilizing.

Question 29

What effect does warming up have on oxygen deficits?

Answer 29

It dec oxygen deficits by increasing blood flow and oxygen delivery, increasing mitochondrial respiration, and enhancing enzymatic activity.

Question 30

What does the ACSM say about reps?

Answer 30

8-12 reps for strength (10-15 in older individuals), higher for endurance.

Question 31

How long do muscle changes take to occur with PRE?

Answer 31

In the first 2 weeks, 90% is due to neural changes. After 6 weeks, 80% is due to inc myofibrils

Question 32

What is the most common problem associated with exercising in the cold?

Answer 32

Hyperthermia