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Exercise.. Don’t Sweat It!. The Engine and Fuel. During exercise, when skeletal muscles contract, they may generate up to 50 pounds of pull. If the muscles of the body are to be active, they need fuel. The fuel is supplied by ATP.
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The Engine and Fuel • During exercise, when skeletal muscles contract, they may generate up to 50 pounds of pull. • If the muscles of the body are to be active, they need fuel. • The fuel is supplied by ATP. • The body must continually replenish the ATP to sustain the activity. • In order to refuel, cells need: • Energy carrying molecules • Oxygen • A way to eliminate wastes • A way to rid themselves of the heat energy which accumulates EVERY body system is used during exercise
ATP • ATP is composed of an adenine nucleotide which is bound to three phosphates. • Much of the energy is stored between the second and third phosphate groups. • As the body exercises, ATP is converted to ADP. • The body must then convert the ADP back to ATP for more energy or fuel. • Since ATP is so crucial in exercise, the body produces it in several ways within the muscle cell. • ATP is derived from the phosphagen system, the glycogen-lactic acid system (glycolysis-fermentation), as well as through aerobic respiration.
The Phosphagen System • As the body begins to exercise, all of the free ATP will be used up by the muscle cell in the first few seconds. • After this, the muscle cell utilizes creatine phosphate which is a high energy phosphate molecule. • Creatine kinase catalyzes the removal of phosphate from the creatine molecule and then the phosphate is moved to an ADP to form ATP. • The cell then uses the energy in the ATP and it is converted back to ADP. • This ADP is then rapidly converted back to ATP for more energy • The phosphagen system can only supply energy needs for 8-10 seconds of exercise as the creatine phosphate levels diminish.
Dietary Creatine • Many people today take dietary creatine. • This is suspected to increase the duration of the effectiveness of the phosphagen system
Anaerobic RespirationPyruvic Acid + NADH => Lactic Acid + NAD+ • After the first 10-15 seconds, muscles must tap into the energy held in the stored glucose molecule to make ATP. • The contracting muscle taking part in the exercise constricts blood flow, and thus the flow of oxygen to the muscle cells. • Thus, the cells breakdown the glucose to make ATP in the absence of oxygen. • Since there is no oxygen involved, this is called anaerobic metabolism. • This system acts very quickly and can provide enough ATP to last 90 seconds. • One product of this reaction is the build up of lactic acid. This causes fatigue and pain in the muscle. • However, the lactic acid is changed to pyruvic acid in the liver. • This system keeps the muscles fueled initially as it takes some time for the heart and lungs to react and increase blood flow and oxygen consumption.
Aerobic Respiration at the 2 Minute Mark • By 2 minutes, the body begins to respond and is sending additional oxygen to the muscle cells that are exercised. • In the presence of oxygen, aerobic respiration can occur. • Aerobic respiration makes more ATP than any other method through the electron transport chain. • The glucose may come from the glycogen supplies in the muscles, the breakdown of glycogen into glucose in the liver, or the absorption of glucose from food in the small intestines • Aerobic respiration can also break down fats and proteins to make ATP. • This supply of ATP can last for hours.
The Responding Systems • Blood flow can be increased by expanding the vessels. • As the byproducts of respiration leave the muscle cells, they stimulate the vessels to expand or dilate. • Blood that would be going to the stomach or kidneys will be diverted to the dilated vessels in the area of the muscles being exercised. • When exercising, the autonomic nervous system stimulates the nerves which enervate the heart. • This causes a constriction of the vessels to the tissues not involved in the activity and a lessening of the blood flow to them.
Heart Rate During Exercise • An increased heart rate also contributes to the increased flow of oxygen carried in the blood to the exercised muscles • During activity the autonomic nervous system stimulates the heart to beat faster and more forcefully increasing the blood flow • The blood flow of the heart increases by about 4 or 5 times faster than it does at its normal resting state.
The Phosphagen System, Glycolysis-Lactic Acid System, and Aerobic Respiration all play a vital role in the production of ATP. While the the contribution of Aerobic Respiration is the greatest, the Glycolysis-Lactic Acid System and the Phosphagen system are initially essential.
Heat • Only 40% of the energy liberated from glucose is used to make ATP. • The other 60% is released as heat energy. • Sweating is an adaptation to release heat energy. • Since water has a high heat of vaporization, much heat energy is lost in the process of evaporating the sweat. • Also, heat energy is transported away from the muscles being exercised by the dilation of the vessels. • This increases blood flow to the surface causes skin to be hot and reddened, enabling heat transfer to the surrounding air. • If someone is exercising in a hot environment,and the heat transfer can not be made to the surrounding air, a person may suffer a heat stroke. • This is when sweating stops, heart rate increases, respiration increases, and the victim becomes confused, nauseous, and dizzy. BEING IN SHAPE IS VITAL
For exercise to occur, ATP must be produced by the body. It acts as the fuel for exercise, just like gas acts as a fuel for a car. To produce this ATP, the body relies on many systems and interactions.
