Muscle Fatigue – Part 1: Research

Muscles become tired during long periods of vigorous activity. This means that they stop contracting efficiently. One cause of this is the build-up of lactic acid in the muscles from anaerobic respiration. The lactic acid is removed from the muscles by blood flowing through them. Muscles use the stored chemical energy of food we eat and convert that to heat and energy of motion

Anaerobic respiration produces an oxygen debt. This is the amount of oxygen needed to oxidise lactic acid to carbon dioxide and water. The existence of an oxygen debt explains why we continue to breathe deeply and quickly for a while after exercise. The source of energy that is used to power the movement of contraction in working muscles is adenosine triphosphate (ATP) – the body’s biochemical way to store and transport energy. However, ATP is not stored to a great extent in cells. So once muscle contraction starts, the making of more ATP must start quickly.

During hard exercise when anaerobic respiration occurs with aerobic respiration, an oxygen debt builds up. This is because glucose is not broken down completely to form carbon dioxide and water. Some of it is broken down to form lactic acid. Panting after exercise provides oxygen to break down lactic acid. The increased heart rate also allows lactic acid to be carried away by the blood to the liver, where it is broken down. When you stop sprinting and start to recover you will actually need more oxygen to recover than your body would have liked to use had enough been available. This is called Excess Post Exercise Oxygen Consumption. After exercise there are other factors causing an increase in oxygen needs as well as repaying the lack of oxygen during exercise.

High altitude is the description given where the athlete begins to experience the limitations that a reduced oxygen intake place upon the body. The human body has a built-in mechanism to counter the effects of low oxygen in the immediate atmosphere. When the body senses that it is not receiving its usual level of oxygen, it determines that it must produce a greater number of red blood cells, which carry oxygen to the bloodstream. The increase of transportation capability means that the body will try to make use of the amount of available oxygen.

Sources:

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/respiration/ respirationrev4.shtml

http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/organism_energy/ respirationrev5.shtml

http://www.teachpe.com/oxygen_debt.php http://www.faqs.org/sports-science/Ha-Ja/High-Altitude-Effects-on-Sport-

Performance.html

Samia B Year 11 Science Homework