A Level Physical Education WJEC

Short-Term Responses to Exercise

Cardio-Pulmonary Responses

• Heart Rate (HR): This is the number of heartbeats per minute. During exercise, the HR rapidly increases to supply the muscles with more oxygen and nutrients.
• Stroke Volume (SV): The amount of blood pumped by the left ventricle of the heart in one contraction. This also increases to meet the demand for oxygen.
• Cardiac Output (CO): It's the product of HR and SV and represents the total volume of blood the heart pumps per minute. This increases during exercise.
• Blood Pressure: Systolic pressure (pressure exerted when the heart contracts) rapidly increases during exercise; diastolic pressure (pressure in the arteries when the heart is at rest) remains relatively stable.
• Respiration Rate: The number of breaths taken per minute. This increases during exercise to increase oxygen supply and to remove waste products.
• Oxygen Uptake (VO2): The amount of oxygen the body utilises from the inhaled air increases during exercise.
• Lactic acid production: A by-product of anaerobic metabolism, its amount quickly elevates during high-intensity exercise.

Muscular Responses

• Increase in muscle temperature: Exercise causes muscles to heat up, promoting enzyme activity and oxygen supply.
• Energy production: In order to keep up with energy demands, muscles increase ATP production through aerobic or anaerobic metabolism.
• Motor unit recruitment: The amount and type of motor units activated increase with the intensity of exercise.
• Lactate Threshold (LT): Yes, it refers to the exercise intensity at which lactate (lactic acid) starts to accumulate in the bloodstream. This occurs quicker at high levels of intense exercise.

Metabolic Responses

• Increased metabolic rate: The rate at which the body metabolises calories from food for immediate use or storage as fat. This rate increases during exercise and can remain elevated for a considerable time afterwards.
• Glycogen Depletion: Muscle and liver glycogen reserves are quickly depleted during intense physical activity.
• Lipolysis: The breaking down of lipids into glycerol and free fatty acids for energy production. This process increases during prolonged, low-intensity exercise.
• Protein Catabolism: Proteins are broken down for energy during prolonged, high-intensity exercise when glycogen stores are depleted.