What Are Muscles?

Date: Aug-20-2012Muscle tissue functions mainly as a source of power and motion in the body. Muscles' main responsibility is for changing or maintaining posture, locomotion, and movement of internal organs. The human body has about 650 muscles, which make up approximately half our bodyweight.

All muscles are basically made of the same material, a kind of elastic tissue; packages of stretchable fiber-like material, similar to what goes into making a rubber band. Each muscle is made of thousands, and sometimes tens of thousands of small musculus fibers. Each muscle fiber is about 40 mm in length and is made up of tiny strands of fibrils.

Each muscle fiber is commanded by a nerve which makes it contract. How strong a muscle is depends mainly on how many fibers are present.

According to Medilexicon's medical dictionary, a Muscle is:

"A primary tissue, consisting predominantly of highly specialized contractile cells, which may be classified as skeletal muscle, cardiac muscle, or smooth muscle; microscopically, the latter is lacking in transverse striations characteristic of the other two types; one of the contractile organs of the body by which movements of the various organs and parts are effected; typical muscle is a mass of musculus fibers (venter or belly), attached at each extremity, by means of a tendon, to a bone or other structure; the more proximal or more fixed attachment is called the origin (q.v.), the more distal or more movable attachment is the insertion (q.v.); the narrowing part of the belly that is attached to the tendon of origin is called the caput or head."

Humans and other vertebrates have three types of muscle: skeletal, smooth and cardiac muscles.
What are skeletal muscles?
Skeletal muscles move the external parts of the body as well as the limbs. Most lay people think of this type when muscles are mentioned. Skeletal muscles give our bodies their shape; they cover our bones, our skeleton.

Skeletal muscles attach themselves to tough tendons which are attached to the bones, or are connected directly to bone. We consciously control this type of muscle; they do what we want when we want.

Virtually all movementswhich are noticeable to the naked eye occur when the skeletal muscles contract, such as moving our eyes, head, arms, fingers, running, walking, and talking, etc.

Our facial expressions, smiles, frowns, mouth and tongue movements are all controlled by our skeletal muscles.

Skeletal muscles are continuously making tiny adjustments to maintain posture; keeping our back straight, or holding our head in the same position. Our bones need to be kept in the right position so that our joints don't dislocate; this is done by the skeletal muscles.

The average male consists of 42% skeletal muscle as the percentage of body mass, and the average female 36%.

Skeletal muscles also generate heat when they contract and release, which helps maintain our body temperature.

Skeletal muscles are divided into two main types:
Type I, red or slow twitch muscles. These are dense and have capillaries. They are rich in myoglobin and mitochondria, which give them their red color. This type of muscle can contract for a long time without much effort. Type I muscles can sustain aerobic activity using carbohydrates and fats as fuel.

Type II fast twitch muscles. There are three main subtypes - Iia, IIx, and IIb. These muscles can contract rapidly and with a lot of force. Contraction is strong but short-lived. Most of our muscle-strength comes from this muscle, as does our increase in mass after periods of weight training. It is the least dense in myoglobin and mitochondria

What are smooth muscles?
Smooth muscles are responsible for movements in the stomach, intestines, arteries, and hollow organs. The smooth muscles in the bowel are also called visceral muscles.

Smooth muscles are activated automatically; we are not aware they are being used, they do not depend on conscious thought, like skeletal muscles are. The smooth muscles in the walls of our intestines contract and push food forward. During childbirth, the smooth muscles in a woman's uterus contract. Our pupils shrink and expand, depending on how much light there, is thanks to smooth muscle movements.

Smooth muscle can also be found within the walls of the bladder, the arrector pili in the skin (makes the hair stand up), and the bronchi.
What are cardiac muscles?
Cardiac muscles are responsible for heartbeat. Cardiac muscles exist only in the heart.

The cardiac muscles work non-stop, day and night, 365 days a year. They work automatically, but are similar in structure to the skeletal muscles.

They make the heart contract so that blood is squeezed out of the heart, and release so that the heart can fill up with blood again.

Making heart muscle cells using skin cells - scientists in Israel in March 2012 reported that they managed to grow healthy heart muscle cells using skin cells from patients with heart failure. They explained that the new heart muscle cells can integrate with existing heart tissue. This opens up the prospect of repairing the damaged hearts of heart failure patients with their own stem cells.
Skeletal muscles and cardiac are striated
Striated muscles consist of thousands of sarcomeres - muscle units. The muscle has a striped (striated) appearance when viewed under a microscope because each sarcomere is made up of parallel bands of different materials. When various bands in the sarcomeres relax or contract, the whole muscle extends or relaxes. Different bands within each muscle interact, allowing the muscle to move powerfully and smoothly.

Often, striated muscle refers just to skeletal muscle, and cardiac muscle is categorized differently.
There are hundreds of muscles in the human body
There are about 650 skeletal muscles in the body, experts say. They add that it is hard to define exactly how many there are, because some single muscles may be more than one of them bunched together. Estimates on the number of muscles vary from 640 to 850.

There are about 650 muscles in the human body

For every skeletal muscle in the human body there is an identical one on the other side. There are about 320 pairs of identical bilateral muscles.
Muscles and exercise
Exercise has several reasons and functions. People may exercise to improve their fitness, bone strength, recover from an injury or illness, to lose weight, improve cardiovascular health, sleep better, to compete in sporting events, or to make their muscles bigger (muscle hypertrophy). There are different types of exercise.

Aerobic exercise - sessions are of long duration with medium-to-low levels of exertion. The muscles are used well below their maximum strength capacity. A marathon is an example of an aerobic activity with very long duration.

Aerobic activities rely mainly on the oxygen (aerobic) system and use a higher proportion of the "slow twitch" (Type I) muscle fibers. Energy consumption comes from carbohydrates, fat and protein. Lots of oxygen is consumed and very little lactic acid is produced.

Anaerobic exercise - in this type of activity, the muscles contract intensely at much nearer their maximum strength. Athletes aiming for improved strength, speed and power will focus more on this type of exercise.

A single anaerobic activity lasts from a few seconds up to a maximum of two minutes. Anything that lasts longer will have a large aerobic metabolic component.

Examples include anaerobic exercise include: weight lifting, sprinting, climbing, and fast skipping (jumping rope).

Anaerobic exercises use "fast-twitch muscle fibers" (Type II muscles) much more. The main fuel sources are ATP or glucose; much less oxygen, fat and protein is used. This type of activity produces lots of lactic acids.

If you focus on anaerobic exercises you will get stronger, while anaerobic exercises will make you fitter. Many sports require a combination of fitness and strength, such as rugby, boxing, wrestling, or judo.
It is never too late to exercise - researchers at Martin-Luther-University of Halle, Germany, explained that exercise among elderly people considerably counteracts muscle breakdown that occurs during old age. They added that exercise for this age-group also increased strength and lowered inflammation caused by aging and heart failure. Dr. Stephan Gielen and team explained that heart failure patients had similar benefits to anybody else who exercises. Age should not be a barrier for regular exercise they stressed.
Exercises for the main muscle groups
Below is a list of the main muscle groups, where they are, what they do, and how to strengthen them.

Abdominal - located in the stomach area. They help you sit up and maintain good posture.

Best exercises - leg raises, crunches (sit ups), twisting crunches

Crunches

Pectoralis - located in the front of the upper chest. They are used when we push up from a lying position or push open a door.

Best exercises - push ups, bench press, dumbbell chest fly.

Bench press

Deltoids - located at the top of the shoulders. They are involved in overhead lifting.

Best exercises - side and rear arm raises, incline dumbbell/barbell bench press, push ups, contralateral limb raises, dumbbell lateral raise, dumbbell (barbell) front raise.

Barbell front raise

Gastrocnemius & Soleus (calf muscles) - located at the back of the lower legs. They help you push off for walking and standing on tip-toes.

Best exercises - standing calf raise, seated calf raise, leg press calf raise, box jumps.

Seated calf raise

Gluteus - the buttock muscles. They help you stand up from a sitting position and climb stairs.

Best exercises - squats, leg press.

Leg press

Hamstrings - located at the back of the thigh. They play a major role in walking.

Best exercises - squats, leg curls, leg extension, lunges.

Lunges

Quadriceps - located at the front of the thigh. They are used when we stand up from a seated position or climb stairs.

Best exercises - squats, leg press, lunges, barbell/dumbbell step ups, cycling.

Dumbbell step-ups

Latissimus Dorsi (lats) & Rhomboids - the lats are the large triangular muscle in the middle of the back. The rhomboids are located between the shoulder blades. We use them when we pull open a door. They also help maintain good posture.

Best exercises - Lats: lat pull downs, chin ups, pull ups.

Chin ups

Trapezius - located in the upper and mid-back. We use this muscle when we move our head sideways.

Best exercises - shoulder shrugs, upright rows.

Upright rows

Erector Spinae - located at the lower back. Helps maintain good posture.

Best exercises - back extensions, bent-over barbell/dumbbell rows, lat pulldown (wide bar), seated row.

Back extensions

Obliques - located on either side of the body. They are involved in rotation and side flexion of the body.

Best exercises - rotary torso, twisting crunches.

Triceps - located at the back (outside) of the upper arm. We use this muscle when we push anything with our arms.

Best exercises - dips, tricep extensions, push ups or bench press (hands close together).

Triceps extensions

Biceps - located in the inside front of the upper arm. They are used in lifting and pullin.

Best exercises - bicep curls, close grip chinup, concentration and preacher curls, hammer curls, dumbbell curls.

Seated bicep curls

Do I need to lift heavy weights for muscle growth?
Most of us believe that the only way to build big muscles is to lift heavy weights. This might be a myth, researchers from McMaster University explained. They found that when properly used,  lighter weights can produce the same muscle-building results as heavy ones.

They say that you have to "pump iron" until you reach muscle fatigue; in other words, work the muscle to exhaustion. Lead researcher, Stuart Phillips, said that rather than grunting and straining with sets of heavy weights, people should try grabbing a much lighter one and keep doing reps until they are unable to lift it anymore.

Phillips said:

"We're convinced that growing muscle means stimulating your muscle to make new muscle proteins, a process in the body that over time accumulates into bigger muscles."

The critical point in building muscle is not how much you lift, but that you tire the muscle to the critical point in fatigue, the researchers emphasized. In their study, some of the participants used weights at 90% of what they could lift, while others lifted weights at only 30% of their maximum lifting capacity.

Weights set at 90% capacity can be lifted five to 10 times before fatigue sets in. At 30%, the participants could do over 24 reps. Those with the light weights had similar muscle gains to the heavy weight lifters.

Written by Christian Nordqvist

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