Running is a heavy energy requiring process. Thus while running a 100m race, there will be a great need of energy to muscles. Thus they will start performing respiration at much higher rate. Due to this reason, there will be increased release of CO2 by muscles.

**Introduction**

During a 100 m race, several physiological changes occur in an athlete's body in order to support the increased demand for energy and oxygen. These changes include increased breathing rate, increased availability of oxygen to muscles, increased production of carbon dioxide by muscles, and increased carbon dioxide concentration in the blood. Let's explore the order in which these changes typically occur.

**Increased Breathing Rate**

The first change that occurs during a 100 m race is an increased breathing rate. As the athlete starts running, their muscles require more oxygen to produce energy. In order to meet this increased demand, the body responds by increasing the rate and depth of breathing. This allows for a greater intake of oxygen into the lungs.

**Increased Availability of Oxygen to Muscles**

Once the breathing rate has increased, the body works to deliver the inhaled oxygen to the muscles. Oxygen is transported to the muscles through the bloodstream, specifically by binding to hemoglobin in red blood cells. The increased breathing rate ensures a higher oxygen intake, which leads to an increased concentration of oxygen in the blood. As a result, more oxygen is available to be delivered to the muscles.

**Increased Production of Carbon Dioxide by Muscles**

During intense exercise, the muscles produce energy through a process called cellular respiration. This process generates carbon dioxide as a waste product. As the athlete continues running, the production of carbon dioxide by the muscles increases. This is because the muscles are working harder and consuming more energy.

**Increased Carbon Dioxide Concentration in Blood**

As the production of carbon dioxide by the muscles increases, the concentration of carbon dioxide in the blood also rises. Carbon dioxide is transported in the blood in the form of bicarbonate ions and dissolved carbon dioxide. The increased concentration of carbon dioxide triggers the body's respiratory system to eliminate excess carbon dioxide by increasing the breathing rate and depth.

**Conclusion**

In summary, the changes that occur in an athlete's body during a 100 m race follow a specific order. The increased breathing rate is the first change to occur, allowing for a greater intake of oxygen. Subsequently, the increased availability of oxygen to the muscles takes place as the oxygen is transported through the bloodstream. The increased production of carbon dioxide by the muscles follows, and finally, the increased carbon dioxide concentration in the blood triggers a further increase in the breathing rate to eliminate excess carbon dioxide. These physiological changes work together to support the athlete's energy demands during the race.