Very Functional

Pulleys and Levers

Know examples of different classes of levers 

1st class - Atlanto axial joint

2nd class - Ankle joint

3rd class - Knee, elbow, shoulder

FLE - fulcrum, load or effort in the middle

3 main components to a lever

1. Axis (fulcrum)

2. Effort (force)

3. Resistance (load)

The load/resistance arm goes from the load to the fulcrum

The effort arm is the distance from the fulcrum to where the muscle attaches, e.g., the bicep tendon attaches to the forearm.  

When the effort arm is shorter than the load arm the mechanical advantage is less than one. This means you will need to exert far greater effort to move the same load. 

*Effort arm can also be called the moment arm 

A mechanical advantage <1  system reduces the apple force (weaker) but increases ROM and speed. 

A mechanical advantage > 1 increases the applied force - less ROM and speed. 

Torque 

• Is a rotational force 

For a rotation force to occur, the force must be perpendicular (90 degrees)

Muscles create an internal torque

Gravity/load creates an external torque 

Isometric - (internal torque and external torque are equal) - no movement at joint. 

Eccentric - (external torque is greater) -  a muscle lengthens under tension, typically to control or decelerate movement against an external force. 

Concentric -  ( Internal torque greater than external) - muscle shortens as it generates force, typically to produce movement.  

Open chain and Closed Chain 

Open - open-chain exercise, the distal end of the limb is free to move while the proximal part remains stable. E.g kicking a ball, leg extension, bicep curl

Closed - the distal end of the limb is fixed (in contact with the ground or an immovable surface), and movement occurs through multiple joints. E.g push up, squat, pull up. 

Length Tension Relationship 

The ability to generate force over a range of motion

When a muscle is at its resting length (does not mean relaxed), it has an optimal overlap between actin and myosin filaments.

This optimal overlap allows for the maximum number of cross-bridges to form between actin and myosin, producing the highest possible tension during contraction.

When a muscle is too shortened (contracted position), the actin filaments overlap too much, and the myosin heads have limited access to binding sites.

This reduced cross-bridge formation results in decreased tension production.

When a muscle is too stretched, the actin and myosin filaments are pulled too far apart, limiting the number of cross-bridges that can form.

*

When improving muscle force we are thinking about levers and length-tension relationship.  

Osteokinematics and arthrokinematics 

Osteokinematics - How a bone is moving around a joint

Arthrokinematics - How the joint surfaces are moving 

Any rotation occurs in the transverse plane of motion (pom) along a longitudinal axis (also known as vertical axis)

Mediolateral axis - aka transverse axis

Antpost axis - aka sagittal axis 

Frontal plane - aka coronal plane

Convex on Concave principle - Arthrokinematics

Terms:

Glide/Slide

Roll

Spin 

Glide and roll are opposite direction - convex on concave

Glide and roll are same direction - concave on convex

Flexion/extension is usually pure spin. 

When arthrokinematics are not working as they should:

• Osteoarthritis can occur

• Osteokinemtaics are not gonna be working as they should, compensations can occur. 

Open chain and closed chain can affect the concave/convex principle. 

E.g - bicep curl - open chain, concave on convex

• Push up - closed chain ( forearm is fixed) convex on concave

Squat Mechanics

Learn the characteristics of the different roles of muscles

Local stabilisers - stabilise the joint deep and local, fatigue resistance, slow twitch, aerobic, feed-forward mechanism

Global mobiliser - mobilise, fast twitch, large ROM 

Common postural movement dysfunction: Local stabilisers are prone to hyperactivity/inhabited and don’t activate as fast. Stability is compromised, so global mobilisers try to perform a stability role where they shouldn’t. 

Abdominal - know this

The canister of the core is made up of 4 muscles

1. Diaphragm 

2. Transverse abdominous - can stabilise when breathing out and the diaphragm is not providing taht stability

3. Pelvic floor 

4. Multifidus 

You can use the diaphragm to increase intrabdominal pressure, bracing the spine and protecting it. 

Stress-Strain Curve (Tendons and Ligaments)

When tendons are relaxed they are crimped (wavey) 

As you increase the load, they will start to straighten, 

At low strain rates, the tendon is more easily deformed and can absorb more mechanical energy. At higher strain rates, it becomes stiffer and more resistant to deformation. 

Classic stress-strain curve demonstrates three phases: 

Toe region - Immediately after applying strain, the crimped collagen fibres are stretched out in the direction of the force applied. 

Linear region - As strain increases elastic deformation occurs during the linear phase. 

Yield region—Microscopic failure of the fibrils usually starts beyond 4% and continues to macroscopically visible failure at 10%.

Recruitment: As axial stretching is applied some of these wave-like fibres begin to straighten increasing the stiffness to the stretch. As the load increases, progressively more fibres in the ligament begin to straighten offering further overall stiffness. (Ligamnets)

Bundles of fibres of ligaments can be orientated in slightly different directions to provide stiffness to a joint at different joint angles and ranges of motion.

Ligamentous creep: When a constant load is applied to a ligament it will elongate relative to the

load applied.

If the load remains constant for a duration of time, the ligament will continue to lengthen up to its maximum length (even though the load applied has not increased)

• Significant implications on the ability of a ligament to protect & stabilise joints in athletes & workers who are subjected to sequential periods of static or cyclic activities during the day, e.g., slouched sitting, repetitive bending, twisting etc.

• Static or repetitive loading with minimal rest has also been shown to cause accumulated micro-damage triggering an inflammatory response within the ligament leading to pain & disability

Clinical Relevance: Athlete: Relative rest, work around the injury

Desk worker: Stand up, walk around, adjust your sitting position. 

Ergonomics 

How you move in the workplace and environment. Adapting the workplace to the person, not the other way around. 

Common contributing factors that can lead to MSK injury include;

1. Awkward positions e.g., a plumber laying a pipe, poor workstation ergonomics

2. Repetitive motions e.g., factory assembly line, typing,

3. Forceful exertions e.g., manually digging a hole

4. Pressure points (e.g., local contact stress) e.g., ill-fitting work shoes

5. Vibration e.g., using a jackhammer, driving over bumpy roads

6. Duration of repetitive or physical tasks (including sitting/standing)

Pressure points -  if you have a direct constant load, the body will adapt in any way possible. E.g direct pressure on the forearm bone, the body lays down more bone tissue to cope with the stress that it is under. 

Fascia

Structure of fascia:

• Fascia is made up of fibres of collagen. elastin and reticulin, which depending on where in the body have varying elasticity, but together build a chaotic web of great flexibility and resilience.

• Ground substance - containing many water-soluble compounds which can trap up to 1000 times their mass of water

• This ground substance acts as a "spacer", so the fibres are not compacted against each other and bind, forming fibrous adhesions.

Cells - mostly fibrocytes, which make the fibres AND the ground substance

Superficial layer - just under the skin

Deep layer - surrounds bones, muscles, nerves and blood vessels

Fascia gives us shape - if layers of fascia is removed the muscle would lose its shape and consistency and therefore its function. 

Why movement is good:

Movement ensures the tissue remains well lubricated as this stimulates cells that produce a lubricating compound called hyaluronic acid that allows the fascial layers to slide and glide, this is vitally important in preventing fascial adhesions. Movement also allows the exchange of water in and out of the tissue helping to maintain tissue resilience and strength. 

When the fascial system is loaded such as when a person stretches or exercises, cells within the fascia are stimulated, resulting in a constant remodelling to cope with the load.

This remodelling helps the fascia to maintain its tensile strength.

If fascia is not put under load i.e., exercise, stretching, massage, foam rolling etc, the fascia will weaken & will lose its ability to slide & glide, leading to adhesions.

• This will impact:

1. Proprioception

2. Joint range of motion

3. A decrease in locomotive propulsion due to reduced elasticity of the tissue.