FOOD AS FUELSAND

THE ENERGY SYSTEMS

FOOD AS FUELS

Where does the body get its energy for movement?

Food is taken into the body as chemical energy and converted to mechanical energy in the form of muscular contractions and movement.

CONVERSION OF FOOD TO ENERGY Our food intake consists of 3 basic nutrients

Carbohydrates, fats and proteins

Carbohydrates, fats and proteins are the only food energy as fuel.

The body also uses water, vitamins and minerals to obtain essential dietary ingredients.

CARBOHYDRATES There are 3 principle types on carbohydrate:

1. Mono-saccharides. Are the simplest form of carbohydrates and absorbed whole without need for breakdown : glucose, galactose and fructose. These simple sugars are found in fruits, vegetables, sugary sweets & drinks.

2. Di-saccharides: Have to be broken down into mono-saccharides before assimilation. They include: Maltose, sucrose and lactose. These are round in

3. Poly-saccharides: are the largest forms of carbohydrate such as starch found in potatoes and forms of dietary fibre and glycogen.

Mono-saccharides such as glucose are the bodies preferred food source particularly during exercise as it is easily assimilated into the blood stream and uses little oxygen.

Athletes who are involved in vigorous endurance events often increase their intake of carbohydrates to increase the bodies stores of energy. This process in called carbohydrate loading.

GLYCAEMIC INDEX (GI)

The GI of a food is determined by measuring the blood glucose response for a uniform period after consumption and comparing this result to consumption of glucose (the most basic form of carbohydrate).

A simple way to visualise this concept is to think of high GI foods as being absorbed fastest and easiest into the blood stream eg. Glucose. Low GI foods require more digestion to breakdown into the fast absorbable forms (glucose, sucrose & galactose).

The GI of a food is influenced by starch structure, fibre content, food processing, physical structure and other macronutrient components (fat and protein).

FAT Found in such foods as butter, margarine, oils, nuts and

animal fats. A main form of fat is triglyceride which is structurally

formed from fatty acids. Three main types of triglyceride are:

1. Saturated fatty acids

2. Mono-unsaturated fatty acids

3. Poly-unsaturated fatty acids Fats are the bodies main source of energy at rest and

during prolonged submaximal exercise.

PROTEIN Found primarily from animal sources in such foods as meat,

fish, eggs and dairy. Lesser quality protein can be found in grains, legumes and some vegetables.

Proteins are not usually used as a fuel, in terms of exercise, it is mainly used for recovery and growth. Protein is also required for hundreds of bodily functions such as: enzymes, hormones, immune cells, oxygen transport, structural components such as hair, skin & nails and much more!

Protein is made up of sub-units called amino acids. There are 20 amino acids, 8 of which are ESSENTIAL, and 12 which are NON-ESSENTIAL. A diet including animal products easily provides all essential amino acids, although vegetarian diets can pose problems in obtaining all the essential amino acids.

HOW FOOD IS CONVERTED INTO ENERGY Food cannot be directly used by the cells it needs to be broken

down by the digestive system.

The digestive system breaks down the foodstuffs, absorbs the

nutrients and transport the waste to the bowel for excretion.

The absorbed energy is carried off via the bloodstream to the

cells of the body.

Some of the fuel is used immediately for energy production

while the remainder is stored n various forms around the body.

FOOD FUEL STORAGE IN THE BODY

Food Fuel Stored as Site

Carbohydrate Glucose GlycogenExcess as adipose tissue

BloodMuscle and liver

Fat Fatty acidsTriglyceridesAdipose Tissue

Blood MuscleAround the body

Protein Muscle Amino acids

Around the body

ADENOSINE TRIPHOSPHATE (ATP)

The most critical chemical function is the manufacturing

of a compound called Adenosine Triphosphate or ATP.

This reaction occurs within the muscles of the body and

releases the energy for all muscle contractions.

The ATP is then stored within the muscles however it is

used up within seconds.

So to ensure that the muscles can continue to contract

ATP must be manufactured by the body.

HOW ATP IS CONVERTED INTO ENERGY Energy release within muscles occurs when ATP loses one

of it’s 3 phosphate groups and forms ADP. This process is called dephosphorylation which releases 7.3 kcal (31 kj) used by cells for energy.

HOW IS ATP MANUFACTURED

The body has three different systems or energy pathways that are

used for manufacturing ATP.

Theses energy systems the anaerobic energy system (which

comprises the ATP-PC system and the lactic acid system) and the

aerobic system.

There are not many activities that utilise just one energy system so

all systems combine and contribute to energy production in most

activities.

The various factors that influence the energy system that is

dominant such as the duration, intensity, athletes fitness level and

whether the individual is resting or exercising.

ATP-PC ENERGY SYSTEMThe ATP-PC system is part of the anaerobic system and provides energy for activities of short duration and high intensity.

The ATP_PC system is the dominant energy system in activities up to 10 seconds in duration and 85-100% of maximum effort.

A limited supply of ATP exists. The ATP-PC system is the pathway used for re-producing ATP from ADP and phosphate. This occurs in muscles via the breakdown of creatine phosphate (CP).

Dominant energy system in events such as 100m sprint, shot put, discus, high jump and long jump.

LACTIC ACID SYSTEM

The lactic acid energy system does not require the presence of oxygen (its anaerobic).

Is the dominant energy system in activities lasting from 30 seconds to 3 minutes in duration.

It uses carbohydrates (glycogen) to remake ATP to produce energy. There is about 2-3 hours worth of glycogen stored in the body. Produces a fatigue causing by product known as lactic acid which is

detrimental to performance.

Dominant energy system in events

such as the 400m and 800m runs.

AEROBIC ENERGY SYSTEM

After 2-3 mins of vigorous exercise the body is able to utilise oxygen to produce energy this is when the aerobic energy system becomes dominant.

The aerobic system will keep supplying ATP for as long as fitness levels allow.

Like the Lactic acid system the aerobic system uses glycogen to produce ATP.

Plenty of oxygen so does not produce lactic acid.

Dominant in events such as distance

runs, swims and bike rides.

PERCENTAGE OF ENERGY PRODUCTION OF EACH SYSTEM THROUGHOUT PHYSICAL ACTIVITY

AT REST As the aerobic energy system can use both

fats and glycogen can be used to provide energy without creating lactic acid the aerobic system is the preferred energy system at rest.

At rest creatine phosphate or CP is being replenished so we can “go hard” again. For example sprint or power throw.

It takes approximately 3 minutes to replenish all CP stores.

During rest all by-products such as lactic acid and hydrodgen ions are being removed as well.

SUMMARY OF MAIN POINTS