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.