Energy Metabolism

Energy metabolism is a series of chemical reactions that result in the breakdown of foodstuffs

(carbohydrate, fat, protein) by which energy is produced, used, and given off as heat.

Roughly, the body is about 20% efficient at trapping energy released. About 80% is released

as heat, which explains why your body heats up quickly when you exercise. A closer look at

your muscle anatomy reveals that the mode of energy storage and energy systems used is

related to your physical activity.

Physical activities can be classified into four basic groups, based on the energy systems that

are used to support these activities.

• Strength-Power: Energy coming from immediate ATP stores. Shot put, power lift, high

jump, golf swing, tennis serve, or a throw; lasting about 0 to 3 seconds of all out

effort.

• Sustained-Power: Energy coming from immediate ATP and CP stores. Sprints, fast

breaks, football lineman; lasting about 0 to 10 seconds of near maximum effort.

• Anaerobic Power-Endurance: Energy coming from ATP, CP, and lactic acid. 200- to

400-meter dash, 100-yard swim; lasting about 1 to 2 minutes.

• Aerobic-Endurance: Energy coming from the oxidative pathway. Events lasting over 2

minutes in duration.

In power events, which last a

few seconds or less, the

muscles depend on the

immediate energy system,

namely ATP and CP reserves.

In speed events, the

immediate and non-oxidative,

or glycolytic energy sources

are utilized. In endurance

events, the immediate and

non-oxidative energy sources

are used, and the oxidative

energy mechanisms become a

more important source of

energy. ATP and CP are

replenished from energy

derived from complete

breakdown of glucose, fatty

acids, and some proteins.

Figure 1-2:Homeostasis example

Metabolism

In order to build biomolecules and sustain life, the body needs energy. The body gets its

energy from the breakdown of nutrients like glucose, amino acids and fatty acids, To construct

molecules there must be molecular destruction going on simultaneously to provide the energy

required to drive these biochemical reactions.

Metabolism: The

chemical processes

occurring within a living

cell or organism that

are necessary for the

maintenance of life. In

metabolism some

substances are broken

down to yield energy

for vital processes while

other substances,

necessary for life, are

synthesized.

Anabolism: The

building up in the body

of complex chemical

compounds from

simpler compounds

(e.g., proteins from

amino acids).

Catabolism: The

breaking down in the

body of complex

chemical compounds

into simpler ones (e.g.,

amino acids to

individual proteins).

The many biochemical processes that make up the body’s metabolism

are categorized into two general phases; anabolism andcatabolism.

From the start, it must be understood that anabolism and catabolism

occur simultaneously all the time. However, they differ in magnitude

depending on the level of activity or rest and on when the last meal

was eaten. When anabolism exceeds catabolism, net growth occurs.

When catabolism exceeds anabolism, the body has a net loss of

substances and body tissues and may lose weight.

Anabolism includes the chemical reactions that combine different

biomolecules to create larger more complex ones. The net result of

anabolism is that new cellular material is made, such as enzymes,

proteins, cell membranes, new cells, and growth of the many tissues.

That energy is stored in the form of glycogen and/or fat, and in muscle

tissue. Anabolism is necessary for growth, maintenance, and repair of

tissues.

Catabolism is the term used to describe the chemical reactions that

break down complex biomolecules into simpler ones for energy

production, to recycling of molecular components, or for their

excretion. Catabolism provides the energy needed for transmitting the

nerve impulses and muscle contraction.

Metabolism includes only the chemical changes that occur within tissue

cells in the body. It does not include those changes to substances that

take place in the digestion of foods in the gastrointestinal system. A

healthy metabolism needs many nutrients to function optimally. A

slight deficiency of even one vitamin can slow down metabolism and

cause chaos throughout the body. The body builds thousands of

enzymes to drive your metabolism in the direction influenced by

activity and nutrition. So, when you are training several hours a day,

you better make sure that

your diet contains the nutrients it needs to feed the many metabolic pathways.

Your Metabolic Set Point

From the discussion of homeostasis and metabolism above, you can see that the body is a tightly run

collection of many biochemical reactions. During the intensive study of weight loss, it was

Is covered that your body seeks to maintain a certain base rate of

metabolism, which has come to be called your metabolic set

point(which results in your basal metabolic rate). This set point is

controlled by your genetics and the environmental factors.

Researchers have demonstrated that you can change your metabolic

set point through dietary means and physical activity.

The metabolic set point is the average rate at which your metabolism

runs, and will result in a body composition set point. People with a

slow metabolism seem to store fat easily, while people with a fast

metabolism seem to be able to eat and never get fat. Your metabolic

set point can be influenced by the external environment (climate),

nutrition, exercise, and other factors. Studies have demonstrated that

when individuals go on a low calorie diet, the body’s metabolic set

point becomes lower to conserve energy. It actually resets itself to

burn fewer calories, thereby conserving energy. Exercise tends to keep

the metabolic rate up, and more aerobic exercise tends to cause the

body to burn more fat for energy.

Metabolic set

point:The base rate of

metabolism that your

body seeks to

maintain; results in

your basal metabolic

rate.

Basal metabolic

rate:The minimum

energy required to

maintain the body’s life

function at rest. Usually

expressed in calories

per hour per square

meter of the body

surface.