MUSCLE BASICS 101
Part 1
Muscles are one of those things that most of us take completely for
granted, but they are incredibly important for two key reasons:
Muscles are the "engine" that your body uses to propel itself.
Although they work differently than a car engine or an electric motor,
muscles do the same thing -- they turn energy into motion.
It
would be impossible for you to do anything without your muscles.
Absolutely everything that you conceive of with your brain is expressed
as muscular motion. The only ways for you to express an idea are with
the muscles of your larynx, mouth and tongue (spoken words), with the
muscles of your fingers (written words or "talking with your hands") or
with the skeletal muscles (body language, dancing, running, building or
fighting, to name a few).
Because muscles are so crucial to
any animal, they are incredibly sophisticated. They are efficient at
turning fuel into motion, they are long-lasting, they are self-healing
and they are able to grow stronger with practice. They do everything
from allowing you to walk to keeping your blood flowing!
When
most people think of "muscles," they think about the muscles that we can
see. For example, most of us know about the biceps muscles in our arms.
But there are three unique kinds of muscle in any mammal's body:
Skeletal muscle is the type of muscle that we can see and feel.
When a body builder works out to increase muscle mass, skeletal muscle
is what is being exercised. Skeletal muscles attach to the skeleton and
come in pairs -- one muscle to move the bone in one direction and
another to move it back the other way. These muscles usually contract
voluntarily, meaning that you think about contracting them and your
nervous system tells them to do so. They can do a short, single
contraction (twitch) or a long, sustained contraction (tetanus).
Smooth muscle is found in your digestive system, blood vessels,
bladder, airways and, in a female, the uterus. Smooth muscle has the
ability to stretch and maintain tension for long periods of time. It
contracts involuntarily, meaning that you do not have to think about
contracting it because your nervous system controls it automatically.
For example, your stomach and intestines do their muscular thing all day
long, and, for the most part, you never know what's going on in there.
Cardiac muscle is found only in your heart, and its big features
are endurance and consistency. It can stretch in a limited way, like
smooth muscle, and contract with the force of a skeletal muscle. It is a
twitch muscle only and contracts involuntarily.
In this
article, we will look at the different types of muscles in your body and
the amazing technology that allows them to work so well. From here on,
we will focus on skeletal muscle. The basic molecular processes are the
same in all three types.
Skeletal-muscle Basics
Skeletal muscle is also called striated muscle, because when it is
viewed under polarized light or stained with an indicator, you can see
alternating stripes of light and dark.
Skeletal muscle has a
complex structure that is essential to how it contracts. We will tease
apart a skeletal muscle, starting with the largest structures and
working our way to the smaller ones.
The basic action of any
muscle is contraction. For example, when you think about moving your arm
using your biceps muscle, your brain sends a signal down a nerve cell
telling your biceps muscle to contract. The amount of force that the
muscle creates varies -- the muscle can contract a little or a lot
depending on the signal that the nerve sends. All that any muscle can do
is create contraction force.
A muscle is a bundle of many
cells called fibers. You can think of muscle fibers as long cylinders,
and compared to other cells in your body, muscle fibers are quite big.
They are from about 1 to 40 microns long and 10 to 100 microns in
diameter. For comparison, a strand of hair is about 100 microns in
diameter, and a typical cell in your body is about 10 microns in
diameter.
A muscle fiber contains many myofibrils, which are
cylinders of muscle proteins. These proteins allow a muscle cell to
contract. Myofibrils contain two types of filaments that run along the
long axis of the fiber, and these filaments are arranged in hexagonal
patterns. There are thick and thin filaments. Each thick filament is
surrounded by six thin filaments.
Thick and thin filaments are
attached to another structure called the Z-disk or Z-line, which runs
perpendicular to the long axis of the fiber (the myofibril that runs
from one Z-line to another is called a sarcomere). Running vertically
down the Z-line is a small tube called the transverse or T-tubule, which
is actually part of the cell membrane that extends deep inside the
fiber. Inside the fiber, stretching along the long axis between
T-tubules, is a membrane system called the sarcoplasmic reticulum, which
stores and releases the calcium ions that trigger muscle contraction.
Part 2 tomorrow
Just what is a Calorie?
A calorie is a unit of energy. We tend to associate calories with food,
but they apply to anything containing energy. For example, a gallon of
gasoline contains about 31,000,000 calories.
So if you
understand that calories give you the energy to move and the sustenance
to build our bodies lets get a closer look at what these calories really
are!
Take the calories from
21 Big Mac Hamburgers and convert them into energy you would have enough
energy to drive a small car approximately 80 miles! So you see foods
harbor a great deal of energy. Eating the right type of calories at the
right time and your body will respond by building lean muscle and
burning fat. Eat the wrong calories at the wrong time and you will lose
muscle and gain fat.
Most of us think of calories in relation
to food, as in "This can of soda has 200 calories." It turns out that
the calories on a food package are actually kilocalories (1,000 calories
= 1 kilocalorie). The word is sometimes capitalized to show the
difference, but usually not. A food calorie contains 4,184 joules. A can
of soda containing 200 food calories contains 200,000 regular calories,
or 200 kilocalories. A gallon of gasoline contains 31,000 kilocalories.
The same applies to exercise -- when a fitness chart says you burn
about 100 calories for every mile you jog, it means 100 kilocalories.
For the duration of this article, when we say "calorie," we mean
"kilocalorie."
What Calories Do
Caloric Breakdown
1 g Carbohydrates: 4 calories
1 g Protein: 4 calories
1 g Fat: 9 calories
1 g Alcohol: 7 calories
Human beings need energy to survive -- to breathe, move, pump blood -- and they acquire this energy from food.
The number of calories in a food is a measure of how much potential
energy that food possesses. A gram of carbohydrates has 4 calories, a
gram of protein has 4 calories, and a gram of fat has 9 calories. Foods
are a compilation of these three building blocks. So if you know how
many carbohydrates, fats and proteins are in any given food, you know
how many calories, or how much energy, that food contains.
If
we look at the nutritional label on the back of a packet of
maple-and-brown-sugar oatmeal, we find that it has 160 calories. This
means that if we were to pour this oatmeal into a dish, set the oatmeal
on fire and get it to burn completely (which is actually pretty tricky),
the reaction would produce 160 kilocalories (remember: food calories
are kilocalories) -- enough energy to raise the temperature of 160
kilograms of water 1 degree Celsius. If we look closer at the
nutritional label, we see that our oatmeal has 2 grams of fat, 4 grams
of protein and 32 grams of carbohydrates, producing a total of 162
calories (apparently, food manufacturers like to round down). Of these
162 calories, 18 come from fat (9 cal x 2 g), 16 come from protein (4
cal x 4 g) and 128 come from carbohydrates (4 cal x 32 g).
Our
bodies "burn" the calories in the oatmeal through metabolic processes,
by which enzymes break the carbohydrates into glucose and other sugars,
the fats into glycerol and fatty acids and the proteins into amino
acids. These molecules are then transported through the bloodstream to
the cells, where they are either absorbed for immediate use or sent on
to the final stage of metabolism in which they are reacted with oxygen
to release their stored energy.
The Basil Metabolic Rate (BMR)
Just how many calories do our cells need to function well? The number
is different for every person. You may notice on the nutritional labels
of the foods you buy that the "percent daily values" are based on a
2,000 calorie diet -- 2,000 calories is a rough average of what a person
needs to eat in a day, but your body might need more or less than 2,000
calories. Height, weight, gender, age and activity level all affect
your caloric needs. There are three main factors involved in calculating
how many calories your body needs per day:
1. Basal metabolic rate
2. Physical activity
3. Thermagenic effect of food
Your basal metabolic rate (BMR) is the amount of energy your body needs
to function at rest. This accounts for about 60 to 70 percent of
calories burned in a day and includes the energy required to keep the
heart beating, the lungs breathing, the kidneys functioning and the body
temperature stabilized. In general, men have a higher BMR than women.
Your Caloric Needs
As you now know, there are three main factors involved in calculating
how many calories your body needs per day: your BMR, physical activity
and the thermic effect of food.
The second factor in the
equation, physical activity, consumes the next highest number of
calories. Physical activity includes everything from making your bed to
jogging. Walking, lifting, bending, and just generally moving around
burns calories, but the number of calories you burn in any given
activity depends on your body weight. Click here for a great table
listing the calories expended in various physical activities and for
various weights.
The thermic effect of food is the final
addition to the number of calories your body burns. This is the amount
of energy your body uses to digest the food you eat -- it takes energy
to break food down to its basic elements in order to be used by the
body.
Calories, Fat and Exercise
So what happens if
you take in more or fewer calories than your body burns? You either gain
or lose fat, respectively. An accumulation of 3,500 extra calories is
stored by your body as 1 pound of fat -- fat is the body's way of saving
energy for a rainy day. If, on the other hand, you burn 3,500 more
calories than you eat, whether by exercising more or eating less, your
body converts 1 pound of its stored fat into energy to make up for the
deficit.
One thing about exercise is that it raises your
metabolic rate not only while you're huffing and puffing on the
treadmill. Your metabolism takes a while to return to its normal pace.
It continues to function at a higher level; your body burns an increased
number of calories for about two hours after you've stopped exercising.
Lots of people wonder if it matters where their calories come from. At
its most basic, if we eat exactly the number of calories that we burn
and if we're only talking about weight, the answer is no -- a calorie is
a calorie. A protein calorie is no different from a fat calorie -- they
are simply units of energy. As long as you burn what you eat, you will
maintain your weight; and as long as you burn more than you eat, you'll
lose weight.
But if we're talking nutrition, it definitely
matters where those calories originate. Carbohydrates and proteins are
healthier sources of calories than fats. Although our bodies do need a
certain amount of fat to function properly -- an adequate supply of fat
allows your body to absorb the vitamins you ingest -- an excess of fat
can have serious health consequences. The U.S. Food and Drug
Administration recommends that a maximum of 30 percent of our daily
calories come from fat. So, if you eat 2,000 calories a day, that's a
maximum of 600 calories from fat, or 67 grams of fat, per day.
This is the base foundation for understanding calories and how calories
play an important role in nutrition. Just remember not to get caught-up
counting the calories as much and you look at the nutritional value of
the calories you choose to eat.
