Energy - ATP (Body's Energy Currency)

As we know all energy originates as light from the sun. Plants convert this into chemical energy through the process photosynthesis. We therefore eat the plants or animals that have eaten these plants, passing the stored energy onto us. In food energy is stored as fat, protein or carbohydrate.

As we know energy is required for many different functions in the body from cell regrowth, muscle repair etc. Muscle is powered by adenosine triphosphate - this is made up from adenosine and tri phosphate groups (3). When hydrolysis occurs (one molecule of ATP mixed with water) the last phosphate group splits away and releases energy. The molecule then becomes adenosine diphosphate or ADP2.

To replenish the ATP levels another phosphate must be introduced, this is called phosphorylation. If this is done with oxygen (o2) it is called aerobic metabolism and without oxygen (o2) it is anaerobic.

Stored ATP in body 100g.

There are four energy sources or substrates used for ATP production.

Creatine Phosphate - readily available and rapidly produces ATP. It is limited to 12g in the body.

Fat - is stored in the adipose tissue (A type of connective tissue that contains stored cellular fat) throughout the body and is a substantial store. Fat is less accessible for cellular metabolism as it must first be reduced from its complex form, triglyceride, to the simpler components of glycerol and free fatty acids. So although fat acts as a vast stockpile of fuel, energy release is too slow for very intense activity.

Carbohydrate - At rest carbs are stored in muscle and the liver, the muscles then convert to glycogen to form ATP. From the liver it will be turned into glucose and transported to muscles via blood. Carbohydrates can realease energy much quicker than fat.

Protein - For protein to be used as energy it it broken down into amino acids and then converted into glucose. Protein cannot supply as much energy as carbohydrate.

The rate at which is energy is released from the substrates is determined by a number of factors. For example, if there are large amounts of one type of fuel available, the body may rely more on this source than on others. The mass action effect is used to describe this phenomenon.

The amount of time is important inbetween exercises to replenish the ATP-CP stores. To replenish fully allow 2mins. This is why you have a break in between all weight training.

Explaining Calories - All energy eventually degrades to heat. The amount of energy we consume and expand is determined as measurement of heat. Energy is measured in calories. A calorie is the amount of heat energy required to raise 1 gram of water by 1degree Celsius.