1. 400 m running, Acids & Bases (The production of lactic acid and its subsequent neutralisation to ensure a stable pH level in muscles)

2. The 400 m, an event which can trace its heritage back to the Ancient Olympic Games of 724 BC, is widely recognised as one of the most physically demanding single athletics races. It is considered to be so demanding because the energy system (anaerobic glycolysis) employed by athletes for sprinting normally only provides energy for 30 to 40 s, a few seconds fewer than it normally takes to complete the distance. The 400 metres

3. Lactate is an unfortunate by-product of anaerobic glycolysis and acids and bases will be explored in the following slides through this link to sport. Lactate itself is not an acid, but it is closely related to the substance lactic acid (which you may have heard sports men and women talk about) and for the purpose of this module they will be considered to be the same for simplification. The 400 metres

4. The body has three main processes in replenishing ATP stores – the energy needed for cells to work and subsequently for muscles to contract. The demand for ATP will determine which process is used by the body. The processes are: ATP PC Anaerobic glycolysis Aerobic glycolysis Energy provision in the body

5. ATP PC – creates ATP quickly but only lasts 6-10 s. This energy system would commonly be used for sudden and very fast muscle contractions needed in very explosive power events such as the 100 m sprint, high jump and long jump. Energy provision in the body (ATP PC, anaerobic and aerobic glycolysis)

6. Anaerobic glycolysis – no oxygen required but only lasts for 30-40 s. An unfortunate by-product of anaerobic glycolysis is lactic acid, which must be removed from muscle cells to ensure continued function. This can be done by providing oxygen to the muscle cells after the anaerobic glycolysis process with a cool-down exercise, keeping well- oxygenated blood circulating to these muscle cells. Energy provision in the body – Anaerobic glycolysis

7. Aerobic glycolysis is the most efficient, but slowest, energy provision process, and requires oxygen. With this process glucose is fully broken down into water and carbon dioxide, which can be removed from the muscle cells easily by the blood. Energy provision in the body – Aerobic glycolysis

8. Acids An acid is a proton, or H +, donor, i.e. it will donate a hydrogen ion to another compound. Lactate, in its acidic form, is lactic acid. It is a H + donor, which makes it an acid, hence its name. Acids and bases

9. Bases A base is a proton, or H +, acceptor, commonly an OH - ion, i.e. it is a compound which will accept the H + ions from an acid. Acids and bases

10.  The pH scale is used to measure whether a solution is acidic or a base.  Pure water at 25 o C has a concentration of H + ions equal to that of OH - ions and this is defined as neutral on the pH scale with a value of 7.0.  Acids have a higher concentration of H + ions than OH - ions and so have a pH value of less than 7.0.  Bases have a lower concentration of H + ions than OH - ions so have a pH value of more than 7.0. pH – the measurement of acidity levels

11. The normal pH level of muscle cells is 7.1, but this reduce to 6.5 with the build up of free H + ions released through the hydrolysation of ATP. The increase of intramuscular lactate concentration also produces an increase in H + ions. The acidic pH level of 6.5 can impair muscle contraction and stimulate nerve endings in the muscles, resulting in the sensation of pain. Changing pH levels in muscle cells due to build up of H + ions

12. The body will neutralise (return to its natural state) the pH level of its muscle cells in two ways – by removing lactic acid, or more accurately lactate, or preventing the build up of it in the first place. Lactate is removed from the local muscle cells, either by being dispersed by the blood to less concentrated areas of the body, or by being taken by the blood to the liver, where it is converted back into glucose. Balancing of pH levels in muscle cells (Lactate removal)

13. Lactate can be prevented from being produced by employing an energy system such as aerobic glycolyis, which does not result in the production of lactate. NB: When insufficient oxygen is available lactate is produced Balancing of pH levels in muscle cells (Prevention of lactate production or accumulation)

14. The accumulation of lactate can also be prevented by ensuring a rapid & continuous supply of oxygen reaches the muscle cells after anaerobic glycolysis has taken place. The oxygen breaks down the lactate to pyruvate, which can be used to fuel a separate energy cycle. A cool-down can help oxygenated blood to reach the required muscle cells quickly. Balancing of pH levels in muscle cells (Prevention of lactate production or accumulation continued)

15. 1.What is the energy system employed by the body that produces lactic acid as a by-product? The energy system that produces lactic acid as a by-product is anaerobic glycolysis. 2.Define the terms acid and base. An acid is: An acid is a proton or hydrogen ion (H + ) donator. A base is: A base is a hydrogen ion (H + ) acceptor, most commonly a hydroxide ion (OH - ). Worksheet answers – Q1 & 2

16. 3.What is the scale used to measure acidity? What value is considered to be neutral on this scale and how is this neutral value determined? The scale used to measure acidity is known as the pH scale. The value 7.0 on this scale is considered to be neutral. This is determined by the fact that at 25 o C pure water has a concentration of H + ions equal to that of OH - ions and has a value of 7.0 on the pH scale. Worksheet answers - Q3

17. 4.The pH value of a muscle cell under normal conditions is 7.1. This can drop to a pH value of 6.5 if extensive amounts of anaerobic glycolysis has taken place. If this happens would the muscle cell be experiencing acidic or alkaline conditions? (Explain your answer). If the muscle cell pH value dropped to 6.5 on the scale the muscle cell would be experiencing acidic conditions. This is because any value under the neutral value of 7.0 on the pH scale is considered to be acidic. Worksheet answers – Q4