Muscle fibers

Muscles

full of tiny fibers that contract. Each tiny fiber has proteins that attach to one another to cause contraction

Muscle contraction

the shortening and exertion of muscle fibers and happens over and over. the work a muscle does to move bones

Skeletal muscle

made of fibers and coverings until you get into the very core, the sarcomere

The sarcomere

the most important structure in muscle contraction, the smallest unit/component of muscle fiber and is the workhorse of the muscle. Some sarcomeres sit side-by-side while others run end-to-end up the muscle fiber.
Sarcomeres make up myofibril

Each sarcomere contains

z-discs, actin, myosin

Z-discs

The end boundaries that mark where one sarcomere begins and ends (like bookends). These are the lines you see in a muscle fiber

Myosin

When a sarcomere shortens

you are contracting/using the muscle

Striations

the visible lines in skeletal muscle tissue. The striations move in the direction of the fibers and the striations are sarcomeres

striations/lines and fibers run in

two different directions

When muscles contract

Neurons tell muscles when to contract
Myosin heads grab onto actin and pull it toward the center
The muscle fibers shorten as actin slides over myosin
Sarcomeres get shorter
The Z-discs move closer together

Key concept

During contraction, muscle fibers shorten. Actin does not lengthen - it slides over the myosin. Sarcomeres do not disappear - they compress. Neurons are active during contraction

The direction of the fibers

show us how the muscle will shorten/contract

Epi-

outer

Peri-

around

Endo-

inner

My-

muscle

Sium-

pertaining to

Iso-

same

Kinetic-

movement

Epimysium

the covering of the whole muscle and extends to be part of the tendon that will attach to the bone. This is what you touch when you hold a muscle in your hand

Endomysium

The inner layer covers each individual muscle fiber

Perimysium

the covering for the bundles of muscle fibers (fascicles)

Muscle fascicles

the bundles of muscle fibers of individual fibers working together as a team. Multiple fascicles bundled together make up the whole muscle you can see and touch
The bundling of fibers give you more strength because the individual fibers help each other

Myofibril

long, thread-like structures. They are inside fibers and contain sarcomeres that do the work of contracting. Every single myofibril has neurons to tell it to work. They never move out of position during contraction

Myoglobin

a protein that acts as storage for oxygen in muscle that are working

Actin

the thin protein fiber that sits above and a bit to the side of myosin

When you have a heavier weight

you feel a bigger contraction in the biceps because you use more sarcomeres and you need more myofibrils and fascicles

Muscle action spectrum

refers to the various types of muscle contractions

Contractions

valuable for muscle strength

2 types of contractions

isometric and isotonic

Isometric contractions

contractions that happen when a muscle is kept at a constant length and the joint is not working through its range of motion.
These usually cause the muscles to burn due to the types of fibers which create lactic acid with no movement.
The length (metric) of the muscle is the same.
Great for measuring pure strength.
A muscle can be stopped during a contraction to maintain the length
Isometric contractions can build muscle at the point in the action that you hold. Positions near the hold are really good for maintaining strength and stability.
Ex: planking, holding a wall sit, pushing against a wall

Isotonic contractions

contractions that work through the range of motion, so the muscle is in motion. This happens when you lift weights. The tension (tonic) or force is the same

Concentric contractions

isotonic contractions in the shortening phase of the lift. The muscle fibers are contracting or getting shorter. This is the lifting or raising phase. This works the muscle in their intended action and builds strength and is the best way to gauge your progress. Ex: toe raise
coming together (shortening)

Eccentric contractions

muscle fibers are getting longer as the muscle contracts (fighting against resistance). This is the lowering or resisting phase. Most efficient at building muscle since it creates microscopic tears and creates bigger myofibrils in the repair process. You have to return the muscle to its relaxed state slowly and deliberately. You can create muscle flexibility. Extreme lifting and stretching can create more myofibrils and more sarcomeres. Ex: resting your heels after a toe raise
extending out (lengthening)

Ex of isotonic contractions

Leg lifts with 10-pound ankle weights, running in a circle for 20 minutes, any movement through a range of motion with resistance

You can shorten the sarcomeres and the myofibrils by

doing flexion and holding it

Isokinetic contraction

The contraction happens at a constant speed to control the lift.
Speed stays consistent even if you push harder.
Great for rehabilitation and controlled training.
An isokinetic machine gives the person lifting the most resistance possible through the whole range of motion.
The more you push/pull the weight, the more resistance you get

Length-tension relationship

helps you determine how to make myosin and actin work better, not harder.
The strength of a muscle contraction depends on how close the actin and myosin are to each other.
If the actin is farther away from the myosin, then fewer myosin heads can grab it which results in less contraction force.
When you are closer, then more heads can grab it and have more force
If the myosin and actin are at the closest that they overlap, the contraction will lessen

When you work on lengthening the muscles by stretching them

you create a greater range of motion for the joint and the muscle has more power or force

Deliberate and indeliberate contractions can be detrimental to the muscle tissue by

tearing fibers in a way that they cannot easily rebuild.

When a muscle is contracted in a forceful or quick action

muscle fascicles/fibers can be stretched or even torn. If you damage a muscle/tendon this way then its called a muscle/tendon strain

When muscles operate in the greatest tension range

they can increase in size

When you lift heavy weights with correct form

that weightlifting causes your muscle fibers to break, which then stimulates a response in the body to repair. This repair is made with bigger protein fibers if you consume correct amino acids

Hypertrophy

an increase in the size of cells that makes the overall enlarge
Ex: lifting weights over time, muscle fibers grow larger/thicken, individual cells get bigger.
Easier because the proteins in the myofibril are gaining in size instead of creating new cells

Hyperplasia

the cells simply increase in number to enlarge the tissue. This means more of all the contractile proteins actin and myosin with more mitochondria and another nucleus.
Hard to achieve because: requires lifting extreme amounts of weight without stopping.
When doing hyperplasia, this creates an intense burn as the lactic acid builds up in the muscles.
Hyperplasia happens anywhere there is an overgrowth of tissue, such as a tumor
Extensive stretching can cause hyperplasia

The nucleus is necessary to

genetically make the proteins that are coded in the new cells and the mitochondria are necessary for the energy to make all this happen

Atrophy

shrinking the muscle by not working out anymore. This happens often because a person gets injured and cannot use the muscle anymore. These proteins are not being used which causes them to diminish in size

Protein synthesis

a process that creates proteins like myosin and actin are made by ribosomes in the cells. This stops when you don't work out the muscles. This diminishes the sarcomeres and myofibrils which causes the muscles to get smaller

Type 1 fibers: referred to as slow twitch fibers and endurance fibers

These fibers have lots of mitochondria (makes energy for the muscle) and have a high concentration of myoglobin (a storage container in the muscle for oxygen). This causes them to have access to more oxygen for the mitochondria to make energy.
This fiber also has a large capillary network to bring more oxygen, water and glucose to the muscle fibers.
Resists fatigue, doesn't contract quickly, has endurance, and built for long haul
More access to oxygen than fast twitch fibers
Best for running a 4 hr marathon, walking a trail for 3 hrs, any activity lasting 2+ hr
Ex: erector spinae muscles running down your spine have type 1 fibers since you stand straight all day and they don't get tired.

Type 2a fibers: aka fast twitch oxidative fibers or middle ground

These fibers also have a large capillary network but they don't have as much mitochondria or myoglobin as type 1.
These fibers are considered aerobic muscles and they have rapid contractions.
The fibers use mitochondria to make energy from oxygen getting the name oxidative.
They are good for quicker and more powerful actions than type 1 fibers.
These fibers are not endurance fibers so they will tire out. These are good for middle distances.
Good oxygen supply with some capillaries
You will use these to go at a higher speed but for a shorter distance.
A runner will benefit from the oxygen-run processes in cellular respiration but not for as long as slow twitch fibers.
Best for jogging a 12 min mile, 800m to 1500m races and activities needing both speed and endurance

Type 2b: aka fast twitch glycolytic fibers or power players

These are good for quick action muscle contractions or power contractions.
They contract quickly and powerfully but not for long. (Glycolysis is the first stage of cellular respiration when the cell is breaking down glucose. If there is not enough oxygen to turn on the Krebs cycle then you will make a small amount of energy and you make the nasty byproduct of lactic acid).
Breaks down glucose for instant energy
Fewer capillaries - less oxygen
These fibers also have rapid contractions but they cannot sustain their contractions since their fibers fatigue quickly.
They don't have much mitochondria or much myoglobin and few capillaries. These fibers are necessary for the spinner.
Not good for activities lasting 2+ hrs
Best for powerlifting, jumping, throwing, performing a 10 sec sprint

Agonist

aka clear major mover or "boss". The major mover that performs the action. The main muscle responsible for the movement. Ex: bicep

Synergist

aka helper or assistant. Assists the agonist muscle. Helps perform the same action and isn't the main mover

Fixator

aka stabilizer or security. This keeps the joint in a stable position so that the agonist can work more easily through the range of motion

Antagonist

aka the reverser. a muscle that can reverse the action. This helps the muscle return to the relaxed position. Must relax when agonist contracts. Must contract to return to starting position Ex: for tricep for bicep

Example 1: Basketball Jump Shot (Elbow Extension)

agonist: Triceps (extends the elbow to shoot)
antagonist: Biceps (flexes the elbow to bring arm back down)
synergist: Anconeus (helps triceps extend elbow)
fixator: Shoulder muscles (stabilize shoulder joint during shot)

Example 2: Ballet Dancer on Toes (Plantar Flexion)

agonist: Gastrocnemius and soleus (calf muscles - major movers going up on toes)
antagonist: Tibialis anterior (brings foot back down - dorsiflexion)
synergist: Small flexors of the foot (help with plantar flexion)
fixator: Quadriceps and hamstrings (stabilize the knee for balance)

Example 3: Yoga Pose (Knee Stabilization)

When quadriceps and hamstrings work together to stabilize the knee during a yoga pose, they are acting as fixators.

Force-couple relationship

The strength of a muscle can come from the help of a different muscle. These muscles can go in different directions. This relationship can also come in the use of a fixator. This is the biomechanical relationship where two or more muscles act on joints from different angles and in opposition which creates a rotational movement

Inflammation

can be felt as pain, puffiness or seen as swelling. Inflammation can be a symptom of a serious underlying issue and when it is paired with intense workout then it can be the body's response to the work the muscles were doing

To build bigger muscles, you need more blood flow. This causes

the heart to pump harder when a period is exercising to get necessary nutrients for the working muscles. These nutrients are imperative for muscle function and include glucose and oxygen for the mitochondria to create energy, sodium, potassium and calcium for the nerves and sarcomeres to cause contraction. Water acts as a solution for the chemical reactions to happen. Then they are delivered to the muscles through the capillaries. These capillaries diffuse the substances into the area where excess fluid is released. This fluid is absorbed by lymph ducts to be cleaned and returned to the bloodstream. This is normal.

When you work the muscles a lot, myofibrils get damaged by muscular enzymes so they can be rebuilt bigger and better. This damage is seen as

an injury to the muscles and the amount of blood plasma released into the damaged muscles increases to fight any infection. There are no infectious agents but they continue to release white blood cells. This becomes a chemical response that increases the fluid released from the capillaries. This fluid presents as swelling which can be seen as minor.

DOMS: delayed onset muscle soreness.

24-72 hrs after workout. Can last a few days to a week
The symptom of DOMS is most likely a result of the tearing of the muscle fibers and the inflammation that ensued.
It goes away because the inflammation was absorbed by the lymph system, the fluid was cleaned in the lymph nodes and then returned to the bloodstream in the heart
Most common after eccentric contractions
Normal response to training when nerves respond to the stimulus

Acute muscle soreness aka metabolic waste-induced pain:

happens during or right after a workout.
This pain is just minimal inflammation and an accumulation of metabolic waste such as lactic acid from your use of the fast twitch glycolytic fibers.
They don't use oxygen for their energy which means in the anaerobic state, they will make very little energy and lots of lactic acid.
Drinking water and stretching can help move the lactic acid out of the muscles to be processed out of the body

Cramps

the body's way of saying the myofibrils are tired or they need something

BCAAS

(branched chain amino acids). Supplements that may help reduce muscle soreness after workouts. Doctors suggest BCAAs when athletes experience excessive muscle soreness and want to recover faster between training sessions

Exercise-associated muscle cramps

the muscles are fatigued. This can be relieved by stretching and massage. Cramps and muscle soreness can be relieved by taking BCAAs. These amino acids assist the ribosomes in creating the proteins that will repair the little tears caused by the intense workout. Glycine, leucine, isoleucine and valine are 4 amino acids that are frontrunner for repair and build bigger muscles and reduce DOMS

Heat cramp

these are due to the increase in heat production during the workout. The body senses the increase in heat and causes you to sweat. This causes a large loss of water and electrolytes (the sodium & potassium you needed for the nerves and muscles). You can relieve this cramp by drinking an electrolyte drink or use ice and a massage

Pain you can accept

fluid-induced pain, metabolic waste-induced pain, cramps and heat-induced pain

Fluid-induced pain

fluid enters your muscles through the capillaries to nourish and repair the tiny tears created by exercise. This fluid leads to swelling and creates a normal soreness after intense exercise. This normally goes away after 48 hours and can be soothed through stretching

Metabolic waste-induced pain

pain during and immediately after a workout results from "feeling the burn" the burn of lactic acid. This pain is acute so you should only feel it during the workout. Drink lots of water and stretching helps flush fiery metabolic waste from the body

Cramps and heat-induced pain

your body will cramp when it needs electrolytes which includes the ones you lose through sweat. Cramps are a targeted pain rather than a general soreness. Replace your electrolytes and water with good nutrition and an electrolyte-replacing drink (or sports drink) can help you too with massaging

Pain sources can be minimized by

starting your workout with lower intensity and gradually increasing or limiting the eccentric work in the early part of the workout

Muscle/tendon strain:

muscles pull the bones needed based on tension.
If the tension is more than the muscle fibers can handle or it's too quick or overused then the myofibrils can stretch too far. This is called a strain and will not be repaired quickly.
You will need to stop using those muscles to let it heal. This can happen to any muscle.

Tendonitis

inflammation in the tendon.
This is a result of overuse of a muscle which puts tension on the tendon.
People would feel a dull ache in the joint that is affected and have a decrease in power or control they have in the joint.
You can heal this with rest, ice and anti-inflammatory meds
Ex: tennis elbow (tendonitis in extensor tendons) this happens when a baseball is repeatedly throwing a ball or extending his elbow and wrist in the throw

Ligament sprain

happens when a person moves a joint in a way that is not allowable without damage.
Any ligament can be damaged by incorrect positioning of the joint since ligaments hold bone to bone.
Ligament sprains are caused by stretching a ligament.
You can tear a ligament if you stretch it too much.
Ex: when a gymnast lands from a front flip but their body continues forward with their feet still planted on the ground. The ACL in the knee would probably sprained or torn

Plantar fasciitis

This is a common ligament issue in the foot.
The plantar fascia is a ligament involved and runs from the heel to the front of your foot.
It is a great shock absorber and helps you support the arch in your foot which helps you walk.
This ligament can be sprained from basically doing anything requiring the plantar flexion action or wearing shoes that do not support the arch

Bone fractures

a transverse fracture - a clean break in two in a straight line.
An oblique fracture - a clean break at a diagonal line.
Breaks can also be a crack (greenstick fracture) or curving around the bone (a spiral fracture).
The bone can be broken into 3+ pieces (a comminuted fracture) or smashed so it is flatted in pieces (a compression fracture).
A bone can be broken in two places with a piece in the middle floating or not attached to anything (a segmental break)
Ex: this can happen due to trauma, falling or direct impact
Treatment: x-ray to diagnose, immobilization and medical treatment

a transverse fracture

a clean break in two in a straight line.

An oblique fracture

a clean break at a diagonal line

greenstick fracture

Breaks can also be a crack

a spiral fracture

curving around the bone

a comminuted fracture

The bone can be broken into 3+ pieces

a compression fracture

smashed so it is flatted in pieces

a segmental break

A bone can be broken in two places with a piece in the middle floating or not attached to anything

Bursitis

an inflammation in the bursa sacs that provide a cushion for the bones to bounce on each other or to alleviate the rubbing of tendons and/or ligaments on the bones in the joint.
When a person repeatedly moves a joint in a particular action, the bursa can be inflamed and the joint becomes swollen.
You can treat this with rest, ice and avoiding aggravating movements

Shin splits: aka medial tibial stress syndrome

These are a common injury for dancers, jumpers or runners since they do plantar flexion a lot which makes the calf muscles bigger.
This can happen suddenly or over time due to overuse.
To heal it, you have to stop doing plantar flexion, rest and wear supportive footwear, and ice

Patellofemoral pain syndrome: aka runner's knee

This is characterized by pain at the inferior edge of the patella.
This is accompanied by a breakdown or the softening of the cartilage that is on the deep side of the patella.
This can cause inflammation in the joint space between the femur and tibia behind the patella.
This pain also comes from the patella
You can treat with with rest, stop stressing the patella tendon, and strengthening exercises

Prevention Tips

Proper hydration: Drink water before and after practice to prevent cramping
Stretching: Stretch muscles before and after practice to prevent strains and cramping
Progressive overload: Gradually increase intensity to avoid overuse injuries
Listen to your body: Rest when injured